Elecsys sFlt-1 and Elecsys PlGF
Device Facts
| Record ID | K241453 |
|---|---|
| Device Name | Elecsys sFlt-1 and Elecsys PlGF |
| Applicant | Roche Diagnostics |
| Product Code | QWH · Clinical Chemistry |
| Decision Date | Feb 7, 2025 |
| Decision | SESE |
| Submission Type | Traditional |
| Regulation | 21 CFR 862.1602 |
| Device Class | Class 2 |
Indications for Use
Immunoassays for the in vitro quantitative determination of the soluble fms-like tyrosine kinase-1/placental growth factor (sFlt-1/PlGF) ratio in human serum. The sFlt-1/PlGF ratio is indicated as an aid in the risk assessment of pregnant women, with a singleton pregnancy (23+0 to 34+6/7 weeks’ gestation) hospitalized for hypertensive disorders of pregnancy (preeclampsia, chronic hypertension with or without superimposed preeclampsia, or gestational hypertension), to develop preeclampsia with severe features within two weeks from testing. The sFlt-1/PlGF ratio should be used in conjunction with clinical assessment and routine laboratory testing. The electrochemiluminescence immunoassay “ECLIA” is intended for use on cobas e immunoassay analyzers.
Device Story
Device consists of two immunoassays (sFlt-1 and PlGF) run on cobas e 411 analyzers; uses electrochemiluminescence technology to quantify sFlt-1 and PlGF in human serum. Input: 20-50 µL patient serum sample; biotinylated/ruthenium-labeled antibodies form sandwich complexes; microparticles capture complexes via biotin-streptavidin interaction; magnetic capture on electrode surface; voltage application induces chemiluminescence measured by photomultiplier. Output: analyte concentrations (pg/mL) used to calculate sFlt-1/PlGF ratio. Used in clinical laboratory settings by trained personnel. Ratio > 38 indicates high risk for severe preeclampsia within two weeks; ratio ≤ 38 indicates low risk. Results aid clinicians in risk stratification and management of hypertensive disorders of pregnancy; used alongside clinical assessment and routine labs.
Clinical Evidence
Prospective, multicenter, blinded, non-interventional study (n=556) evaluated clinical performance in pregnant women (23+0 to 34+6/7 weeks) hospitalized for hypertensive disorders. Primary endpoint: development of severe preeclampsia within two weeks. Results: Sensitivity 91.4% (95% CI: 86.4-95.0), Specificity 77.3% (95% CI: 72.7-81.5), PPV 66.9%, NPV 94.7%. Prevalence of severe preeclampsia was 33%.
Technological Characteristics
Sandwich immunoassay; electrochemiluminescence (ECLIA) detection; ruthenium complex label; streptavidin-coated microparticles. Dimensions/form factor: rackpack reagent system. Connectivity: cobas e immunoassay analyzers. Software: automated instrument-specific calibration and master curve via reagent barcode. Materials: monoclonal antibodies (mouse), phosphate buffer, preservatives. Biotin tolerance up to 1200 ng/mL.
Indications for Use
Indicated for pregnant women, singleton pregnancy (23+0 to 34+6/7 weeks' gestation), hospitalized for hypertensive disorders of pregnancy (preeclampsia, chronic hypertension, or gestational hypertension), to assess risk of developing preeclampsia with severe features within two weeks.
Regulatory Classification
Identification
A prognostic test for development or progression of preeclampsia is an in vitro diagnostic device intended to measure one or more analytes obtained from human samples. A prognostic test for development or progression of preeclampsia is indicated as an aid in the risk assessment for the development or progression of preeclampsia. This device is not intended for diagnosis of any disease.
Predicate Devices
- B·R·A·H·M·S sFlt-1/ PlGF KRYPTOR Test System (DEN220027)
Related Devices
- DEN220027 — B·R·A·H·M·S sFlt-1/ PlGF KRYPTOR Test System · Brahms GmbH, Part of Thermo Fisher Scientific · May 18, 2023
- K963770 — BIOCIRCUITS IOS QUANTITATIVE HCG TEST CARTRIDGES/BIOCIRCUITS IOS IMMUNOASSAY CONTROLS · Biocircuits Corp. · Dec 5, 1996
- K060548 — STRATUS CS ACUTE CARE BETAHCG AND NT-PROBNP TESTPAK AND TESTPAK ASSAY, CALPAK AND DILPAK · Dade Behring, Inc. · Apr 6, 2006
Submission Summary (Full Text)
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FDA
U.S. FOOD & DRUG
ADMINISTRATION
# 510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY
ASSAY ONLY
## I Background Information:
A 510(k) Number
K241453
B Applicant
Roche Diagnostics
C Proprietary and Established Names
Elecsys sFlt-1 and Elecsys PlGF
D Regulatory Information
| Product Code(s) | Classification | Regulation Section | Panel |
| --- | --- | --- | --- |
| QWH | Class II | 21 CFR 862.1602 - Prognostic Test For Development Or Progression Of Preeclampsia | TX - Clinical Toxicology |
## II Submission/Device Overview:
A Purpose for Submission:
New Device
B Measurand:
Soluble fms-like tyrosine kinase-1 (sFlt-1)
Placental growth factor (PlGF)
C Type of Test:
Immunofluorescent quantitative assay
Food and Drug Administration
10903 New Hampshire Avenue
Silver Spring, MD 20993-0002
www.fda.gov
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K241453 - Page 2 of 19
## III Intended Use/Indications for Use:
### A Intended Use(s):
See Indications for Use below.
### B Indication(s) for Use:
Immunoassays for the in vitro quantitative determination of the soluble fms-like tyrosine kinase-1/placental growth factor (sFlt-1/PlGF) ratio in human serum. The sFlt-1/PlGF ratio is indicated as an aid in the risk assessment of pregnant women, with a singleton pregnancy (23+0 to 34+6/7 weeks’ gestation) hospitalized for hypertensive disorders of pregnancy (preeclampsia, chronic hypertension with or without superimposed preeclampsia, or gestational hypertension), to develop preeclampsia with severe features within two weeks from testing. The sFlt-1/PlGF ratio should be used in conjunction with clinical assessment and routine laboratory testing.
The electrochemiluminescence immunoassay “ECLIA” is intended for use on cobas e immunoassay analyzers.
### C Special Conditions for Use Statement(s):
Rx- For Prescription Use Only
The Elecsys sFlt-1 assay should be used only with the Elecsys PlGF assay and the Elecsys PlGF should be used only with the Elecsys sFlt-1 assay to calculate the ratio (sFlt-1/PlGF).
The ratio must be calculated using Elecsys sFlt-1 and Elecsys PlGF results obtained on the same patient sample and the same immunoassay analyzer.
The assays are not intended to be used individually.
Patient samples should not be diluted.
Do not use gel separation tubes as the performance in this sample type has not been established.
For in vitro diagnostic use only.
### D Special Instrument Requirements:
Cobas e 411 immunoassay analyzer
## IV Device/System Characteristics:
### A Device Description:
The device is comprised of the Elecsys sFlt-1 assay and the Elecsys PlGF assay. Elecsys sFlt-1 and PlGF assays are supplied as two reagent packs that are run on the cobas e immunoassay analyzer. Each reagent pack is sufficient for 100 determinations, and is comprised of a bundle of three reagent bottles as a single unit:
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sFlt-1
- Reagent M- 1 bottle, 6.5 mL: streptavidin-coated microparticles 0.72 mg/mL; preservative
- Reagent R1- 1 bottle, 9 mL: biotinylated monoclonal anti-sFlt-1 antibody (mouse) 0.5 mg/L; phosphate buffer 100 mmol/L, pH 7.2; preservative
- Reagent R2- 1 bottle, 9 mL: monoclonal anti-sFlt-1 antibody (mouse) labeled with ruthenium complex 1.0 mg/L; biotin scavenger antibody 0.7 mg/mL; phosphate buffer 100 mmol/L, pH 7.2; preservative
PlGF
- Reagent M- 1 bottle, 6.5 mL: streptavidin-coated microparticles 0.72 mg/mL; preservative
- Reagent R1- 1 bottle, 8 mL: biotinylated monoclonal anti- PlGF antibody (mouse) 0.6 mg/L; phosphate buffer 50 mmol/L, pH 6.0; preservative
- Reagent R2- 1 bottle, 8 mL: monoclonal anti- PlGF antibody (mouse) labeled with ruthenium complex 4.0 mg/L; biotin scavenger antibody 1.0 mg/mL; phosphate buffer 50 mmol/L, pH 6.0; preservative
Additional materials required but not provided are calibrators (CalSet sFlt-1 and CalSet PlGF) and analyte controls (Elecsys PreciControl Multimarker.
B Principle of Operation:
Elecsys sFlt-1 and PlGF assays are sandwich immunoassays based on electrochemiluminescence technology. Each assay takes 18 minutes to complete and are run on the cobas e 411 immunoassay analyzer.
1st incubation:
sFlt-1: 20 µL of sample, a biotinylated monoclonal sFlt-1-specific antibody and a monoclonal sFlt-1- specific antibody labeled with a ruthenium complex react to form a sandwich complex. PlGF: 50 µL of sample, a biotinylated monoclonal PlGF-specific antibody and a monoclonal PlGF-specific antibody labeled with a ruthenium complex react to form a sandwich complex.
2nd incubation: After addition of streptavidin-coated microparticles, the complex becomes bound to the solid phase via interaction of biotin and streptavidin.
The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell. Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier.
Results are determined via instrument-specific calibration curves which are generated by 2-point calibration and a master curve provided via the reagent barcode or e-barcode.
The sFlt-1/PlGF ratio is either manually calculated or programmed as a calculated test in the instrument software or the Laboratory Information System (LIS).
V Substantial Equivalence Information:
K241453 - Page 3 of 19
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K241453 - Page 4 of 19
A Predicate Device Name(s):
B·R·A·H·M·S sFlt-1/ PlGF KRYPTOR Test System
B Predicate 510(k) Number(s):
DEN220027
C Comparison with Predicate(s):
| Device & Predicate Device(s): | K241453 | DEN220027 |
| --- | --- | --- |
| Device Trade Name | Elecsys sFlt-1 and Elecsys PlGF | B·R·A·H·M·S sFlt-1/ PlGF KRYPTOR Test System |
| General Device Characteristic Similarities | | |
| Intended Use/Indications For Use | Quantitative determination of the soluble fms like tyrosine kinase-1/placental growth factor (sFlt-1/PlGF) ratio. The sFlt-1/PlGF ratio is indicated as an aid in the risk assessment of pregnant women, with a singleton pregnancy (23+0 to 34+6/7 weeks’ gestation) hospitalized for hypertensive disorders of pregnancy (preeclampsia, chronic hypertension with or without superimposed preeclampsia, or gestational hypertension), to develop preeclampsia with severe features within two weeks from testing. The sFlt-1/PlGF ratio should be used in conjunction with clinical assessment and routine laboratory testing. | Same |
| Methodology | Quantitative immunofluorescent | Same |
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| | assay | |
| --- | --- | --- |
| General Device Characteristic Differences | | |
| Sample Type | Human serum | Human serum/plasma |
| Clinical cut-off | sFlt-1/PlGF ratio = 38 | sFlt-1/PlGF ratio = 40 |
| Measuring Range | sFlt-1:80-85,000 pg/mL
PlGF:10-5,400 pg/mL | sFlt-1: 315-90,000 pg/mL
PlGF: 7.6-4,000 pg/mL |
VI Standards/Guidance Documents Referenced:
Clinical & Laboratory Standards Institute (CLSI) EP05-A3, Evaluation of Precision Performance of Quantitative Measurement Methods; Approved Guideline - Third Edition.
CLSI EP06, Evaluation of Linearity of Quantitative Measurement Procedures, 2nd Edition.
CLSI EP07, Interference Testing in Clinical Chemistry, 3rd edition.
CLSI EP17-A2, Evaluation of Detection Capability for Clinical Laboratory Measurement Procedures; Approved Guideline - Second Edition.
ISO 17511, In vitro diagnostic medical devices — Requirements for establishing metrological traceability of values assigned to calibrators, trueness control materials and human samples.
VII Performance Characteristics (if/when applicable):
A Analytical Performance:
1. Precision/Reproducibility:
Precision - Single-site study:
Repeatability and within-laboratory precision was evaluated based on recommendations per CLSI guideline EP05-A3. Ten human serum sample pools from pregnant women and non-pregnant women (six native and four spiked) and two controls were tested with the Elecsys sFlt-1 and Elecsys PlGF assays. Each sample was tested in duplicates per run, two runs per day, across 21 days, on one cobas e411 immunoassay analyzer using one reagent lot for a total of 84 replicates per concentration.
Results were analyzed by balanced two-way nested ANOVA. Results for sFlt-1, PlGF, and the sFlt-1/PlGF ratio are shown below.
K241453 - Page 5 of 19
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sFlt-1
| Sample | Mean (pg/mL) | Repeatability | | Within-laboratory precision | |
| --- | --- | --- | --- | --- | --- |
| | | SD (pg/mL) | % CV | SD (pg/mL) | % CV |
| Serum 9 | 78.6 | 1.9 | 2.3 | 2.8 | 3.5 |
| Serum 4* | 89.3 | 2.0 | 2.3 | 3.2 | 3.5 |
| Serum 10 | 90.7 | 2.0 | 2.2 | 3.3 | 3.7 |
| Control 1 | 106 | 2.1 | 2.0 | 3.0 | 2.8 |
| Serum 2 | 632 | 6.5 | 1.0 | 11.1 | 1.8 |
| Control 2 | 1044 | 9.5 | 0.9 | 17.3 | 1.7 |
| Serum 1 | 1690 | 21.1 | 1.2 | 28.2 | 1.7 |
| Serum 8 | 2522 | 28.6 | 1.1 | 46.0 | 1.8 |
| Serum 9 | 3867 | 43.0 | 1.1 | 74.1 | 1.9 |
| Serum 7 | 18037 | 246.0 | 1.4 | 405.0 | 2.2 |
| Serum 5 | 36992 | 682.0 | 1.8 | 1287.0 | 3.5 |
| Serum 6 | 76873 | 1870.0 | 2.4 | 2842.0 | 3.7 |
*One replicate was excluded from analyses due to concentrations below the reportable range of PlGF.
PIGF
| Sample | Mean (pg/mL) | Repeatability | | Within-laboratory precision | |
| --- | --- | --- | --- | --- | --- |
| | | SD (pg/mL) | % CV | SD (pg/mL) | %CV |
| Serum 4 | 11.8 | 0.7 | 5.7 | 1.2 | 9.9 |
| Serum 6 | 39.4 | 1.1 | 2.7 | 2.1 | 5.3 |
| Serum 1 | 46.3 | 1.0 | 2.2 | 1.5 | 3.3 |
| Serum 5 | 74.0 | 1.9 | 2.5 | 4.1 | 5.6 |
| Serum 8 | 74.7 | 1.3 | 1.8 | 2.3 | 3.1 |
| Serum 2 | 89.9 | 1.2 | 1.3 | 2.0 | 2.3 |
| Serum 7 | 96.0 | 1.6 | 1.6 | 2.4 | 2.5 |
| Control 1 | 96.9 | 1.5 | 1.5 | 2.3 | 2.3 |
| Serum 3 | 441 | 4.5 | 1.0 | 7.3 | 1.7 |
| Control 2 | 950 | 8.7 | 0.9 | 17.1 | 1.8 |
| Serum 9 | 4923 | 78.4 | 1.6 | 116.0 | 2.4 |
| Serum 10 | 8894 | 141.0 | 1.6 | 178.0 | 2.0 |
K241453 - Page 6 of 19
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sFlt-1/PlGF Ratio
| Sample | Mean ratio | Repeatability | | Within-laboratory precision | |
| --- | --- | --- | --- | --- | --- |
| | | SD | CV % | SD | CV % |
| Serum 10 | 0.01 | 0.0003 | 2.5 | 0.0004 | 3.7 |
| Serum 9 | 0.02 | 0.0005 | 2.9 | 0.0005 | 3.4 |
| Control 1 | 1 | 0.025 | 2.3 | 0.026 | 2.3 |
| Control 2 | 1 | 0.015 | 1.4 | 0.017 | 1.5 |
| Serum 2 | 7 | 0.1 | 1.7 | 0.1 | 1.9 |
| Serum 4 | 8 | 0.4 | 4.9 | 0.5 | 7.0 |
| Serum 3 | 9 | 0.1 | 1.1 | 0.1 | 1.4 |
| Serum 8 | 34 | 0.5 | 1.5 | 0.8 | 2.4 |
| Serum 1 | 37 | 0.7 | 2.0 | 1.0 | 2.7 |
| Serum 7 | 188 | 3.0 | 1.6 | 3.9 | 2.1 |
| Serum 5 | 501 | 17.9 | 3.6 | 27.4 | 5.5 |
| Serum 6 | 1957 | 71.8 | 3.7 | 101.0 | 5.1 |
Lot-to-lot variability - Single-site study:
Lot-to-lot variability of Elecsys sFlt-1 and Elecsys PlGF was evaluated on one cobas e 411 analyzer using three reagent lots. Ten human serum pools and two levels of controls were tested for five days, one run per day, with five replicates per run for a total of 75 replicates per sample.
Results were analyzed by balanced two-way nested ANOVA. Results for sFlt-1, PlGF, and the sFlt-1/PlGF ratio for the combined lots are shown below.
sFlt-1
| Sample | Mean pg/mL | Repeatability | | Between-Day | | Between lot | | Total | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | | SD | CV % | SD | CV % | SD | CV % | SD | CV % |
| Serum 9 | 80.1 | 2.5 | 3.1 | 0.1 | 0.1 | 0.8 | 1.0 | 2.6 | 3.3 |
| Serum 4 | 90.5 | 2.4 | 2.7 | 0 | 0 | 1.1 | 1.2 | 2.6 | 2.9 |
| Serum 10 | 92.7 | 4.1 | 4.4 | 0.2 | 0.2 | 0 | 0 | 4.1 | 4.4 |
| Control 1 | 109 | 2.7 | 2.5 | 0.0 | 0.0 | 2.0 | 1.8 | 3.4 | 3.1 |
| Serum 2 | 643 | 10.1 | 1.6 | 0.0 | 0.0 | 1.0 | 0.2 | 10.1 | 1.6 |
| Control 2 | 1056 | 13.8 | 1.3 | 12.4 | 1.2 | 0.0 | 0.0 | 18.6 | 1.8 |
| Serum 1 | 1691 | 27.5 | 1.6 | 0.0 | 0.0 | 0.0 | 0.0 | 27.5 | 1.6 |
| Serum 8 | 2507 | 40.1 | 1.6 | 0.0 | 0.0 | 13.8 | 0.6 | 42.4 | 1.7 |
| Serum 3 | 3863 | 52.8 | 1.4 | 2.9 | 0.7 | 21.8 | 0.6 | 57.2 | 1.5 |
| Serum 7 | 17827 | 262 | 1.5 | 93.2 | 0.5 | 284 | 1.6 | 397 | 2.2 |
| Serum 5 | 36258 | 1183 | 3.3 | 334 | 0.9 | 452 | 1.3 | 1310 | 3.6 |
| Serum 6 | 75752 | 2284 | 3.0 | 427 | 0.6 | 930 | 1.2 | 2503 | 3.3 |
K241453 - Page 7 of 19
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PIGF
| Sample | Mean pg/mL | Repeatability | | Between-Day | | Between lot | | Total | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | | SD | CV % | SD | CV % | SD | CV % | SD | CV % |
| Serum 4 | 11.7 | 1.0 | 8.4 | 0.0 | 0.0 | 0.1 | 0.8 | 1.0 | 8.4 |
| Serum 6 | 37.6 | 0.8 | 2 | 0.4 | 1.1 | 0.4 | 1 | 1.0 | 2.5 |
| Serum 1 | 46.6 | 1.3 | 2.7 | 0.0 | 0.0 | 0.4 | 0.8 | 1.4 | 3 |
| Serum 5 | 68.4 | 3.0 | 4.4 | 0.0 | 0.0 | 0.9 | 1.3 | 3.2 | 4.6 |
| Serum 8 | 75.5 | 1.8 | 2.4 | 0.0 | 0.0 | 0.7 | 0.9 | 2.0 | 2.6 |
| Serum 2 | 91.9 | 2.1 | 2.3 | 0.0 | 0.0 | 1.1 | 1.2 | 2.4 | 2.6 |
| Serum 7 | 97.2 | 2.1 | 2.2 | 0.0 | 0.0 | 0.8 | 0.8 | 2.3 | 2.3 |
| Control 1 | 98.6 | 2.0 | 1.9 | 0.0 | 0.0 | 1.6 | 1.6 | 2.5 | 2.6 |
| Serum 3 | 444 | 6.8 | 1.5 | 2.9 | 0.6 | 5.3 | 1.2 | 9.1 | 2.1 |
| Control 2 | 971 | 16 | 1.7 | 1.1 | 0.1 | 13.1 | 1.3 | 20.7 | 2.1 |
| Serum 9 | 4901 | 121 | 2.5 | 0.0 | 0.0 | 29.2 | 0.6 | 125 | 2.6 |
| Serum 10 | 8882 | 200 | 2.3 | 0.0 | 0.0 | 108 | 1.2 | 227 | 2.6 |
sFlt-1/PIGF Ratio
| Sample | Mean | Repeatability | | Between-Day | | Between lot | | Total | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | | SD | CV % | SD | CV % | SD | CV % | SD | CV % |
| Serum 10 | 0.01 | 0.0005 | 4.5 | 0.0005 | 0.8 | 0.00005 | 0.5 | 0.0005 | 4.6 |
| Serum 9 | 0.02 | 0.0006 | 3.6 | 0.0006 | 0.0 | 0.0002 | 1.0 | 0.0006 | 3.7 |
| Control 2 | 1.1 | 0.01 | 1.3 | 0.01 | 0.6 | 0.01 | 1.0 | 0.02 | 1.8 |
| Control 1 | 1.1 | 0.02 | 2.0 | 0.01 | 0.5 | 0.003 | 0.3 | 0.02 | 2.1 |
| Serum 2 | 7.0 | 0.1 | 1.8 | 0.1 | 0.7 | 0.1 | 1.1 | 0.2 | 2.2 |
| Serum 4 | 7.8 | 0.5 | 6.6 | 0.1 | 0.9 | 0.0 | 0.0 | 0.5 | 6.7 |
| Serum 3 | 8.7 | 0.1 | 1.2 | 0.1 | 0.7 | 0.2 | 1.8 | 0.2 | 2.3 |
| Serum 8 | 33.2 | 0.6 | 1.8 | 0.0 | 0.0 | 0.5 | 1.5 | 0.8 | 2.4 |
| Serum 1 | 36.3 | 0.8 | 2.1 | 0.1 | 0.2 | 0.4 | 1.0 | 0.9 | 2.4 |
| Serum 7 | 183 | 3.3 | 1.8 | 0.5 | 0.3 | 4.6 | 2.5 | 5.7 | 3.1 |
| Serum 5 | 531 | 26.9 | 5.1 | 0.0 | 0.0 | 13.6 | 2.6 | 30.2 | 5.7 |
| Serum 6 | 2015 | 72.6 | 3.6 | 0.0 | 0.0 | 48.5 | 2.4 | 87.3 | 4.3 |
Reproducibility - Multi-site study:
A three-site reproducibility study was conducted using ten human serum sample pools from pregnant women and non-pregnant women (six native and four spiked) and two controls with the Elecsys sFlt-1 and Elecsys PIGF assays on cobas e411 immunoassay analyzers. Testing was performed using three reagent lots, one lot of calibrator, and one lot of controls at each site with each sample assayed in replicates of five per run, one run per day over five days, for a total of 75 replicates (per sample per site).
K241453 - Page 8 of 19
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Results were analyzed by crossed-nested ANOVA. Results for sFlt-1, PlGF, and the sFlt-1/PlGF ratio for the combined sites are shown below.
sFlt-1
| Sample | Mean (pg/mL) | Repeatability | | Between-day | | Within-site | |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | SD | %CV | SD | %CV | SD | %CV |
| Serum 4 | 94 | 3.3 | 3.5 | 0.9 | 1.0 | 3.4 | 3.6 |
| Control 1 | 110 | 2.7 | 2.2 | 1.4 | 1.3 | 3.1 | 2.8 |
| Serum 5 | 111 | 3.0 | 2.7 | 1.0 | 0.9 | 3.2 | 2.8 |
| Control 2 | 1062 | 22.5 | 2.1 | 11.6 | 1.1 | 25.3 | 2.4 |
| Serum 1 | 2010 | 55 | 2.7 | 15.4 | 0.8 | 57.2 | 2.8 |
| Serum 8 | 2048 | 54.8 | 2.7 | 21 | 1.0 | 58.7 | 2.9 |
| Serum 9 | 2063 | 43.1 | 2.1 | 13.5 | 0.7 | 45.1 | 2.2 |
| Serum 2 | 2179 | 46.5 | 2.1 | 22.3 | 1.0 | 51.6 | 2.4 |
| Serum 3 | 3427 | 78.1 | 2.3 | 31.8 | 0.9 | 84.4 | 2.5 |
| Serum 10 | 17603 | 489.0 | 2.8 | 0.0 | 0.0 | 489.0 | 2.8 |
| Serum 6 | 28122 | 927.0 | 3.3 | 345.0 | 1.2 | 989.0 | 3.5 |
| Serum 7 | 73980 | 3597.0 | 4.9 | 1653.0 | 2.2 | 3959.0 | 5.4 |
| Sample | Mean (pg/mL) | Between-lot | | Between-site | | Reproducibility | |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | SD | %CV | SD | %CV | SD | %CV |
| Serum 4 | 94 | 1.9 | 2.0 | 0.4 | 0.4 | 3.9 | 4.2 |
| Control 1 | 110 | 3.5 | 3.2 | 0.8 | 0.7 | 4.8 | 4.3 |
| Serum 5 | 111 | 2.2 | 2.0 | 0.5 | 0.4 | 3.8 | 3.5 |
| Control 2 | 1062 | 16.5 | 1.6 | 6.3 | 0.6 | 30.9 | 2.9 |
| Serum 1 | 2010 | 21.8 | 1.1 | 28.0 | 1.4 | 67.3 | 3.4 |
| Serum 8 | 2048 | 24.6 | 1.2 | 39.2 | 1.9 | 74.7 | 3.7 |
| Serum 9 | 2063 | 24.0 | 1.2 | 22.5 | 1.1 | 55.8 | 2.7 |
| Serum 2 | 2179 | 24.9 | 1.1 | 33.1 | 1.5 | 66.2 | 3.0 |
| Serum 3 | 3427 | 37.0 | 1.1 | 35.0 | 1.0 | 98.6 | 2.9 |
| Serum 10 | 17603 | 282.0 | 1.6 | 229.0 | 1.3 | 609.0 | 3.5 |
| Serum 6 | 28122 | 160.0 | 0.6 | 461.0 | 1.6 | 1103.0 | 3.9 |
| Serum 7 | 73980 | 1512.0 | 2.0 | 3783.0 | 5.1 | 5681.0 | 7.7 |
PIGF
| Sample | Mean (pg/mL) | Repeatability | | Between-day | | Within-site | |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | SD | %CV | SD | %CV | SD | %CV |
| Serum 4 | 9.4 | 0.8 | 8.9 | 0.5 | 4.8 | 0.9 | 10.1 |
| Serum 7 | 31.7 | 1.1 | 3.6 | 0.5 | 1.5 | 1.2 | 3.9 |
| Serum 6 | 33.2 | 1.4 | 4.3 | 0.6 | 1.7 | 1.5 | 4.6 |
| Serum 9 | 41 | 1.2 | 2.9 | 0.5 | 1.2 | 1.3 | 3.1 |
| Serum 1 | 44.2 | 1.2 | 2.6 | 0.7 | 1.7 | 1.4 | 3.1 |
| Serum 10 | 96 | 2.4 | 2.5 | 1.0 | 1.1 | 2.6 | 2.7 |
| Control 1 | 99 | 2.0 | 2.0 | 1.2 | 1.2 | 2.3 | 2.3 |
| Serum 2 | 243 | 4.8 | 2.0 | 3.7 | 1.5 | 6.1 | 2.5 |
| Serum 3 | 531 | 9.8 | 1.9 | 7.7 | 1.5 | 12.5 | 2.4 |
| Control 2 | 970 | 19.0 | 2.0 | 14.3 | 1.5 | 23.8 | 2.5 |
K241453 - Page 9 of 19
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| Serum 5 | 4913 | 113.0 | 2.3 | 81.1 | 1.7 | 139.0 | 2.8 |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Serum 8 | 8826 | 222.0 | 2.5 | 128.0 | 1.5 | 256.0 | 2.9 |
| Sample | Mean (pg/mL) | Between-lot | | Between-site | | Reproducibility | |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | SD | %CV | SD | %CV | SD | %CV |
| Serum 4 | 9.4 | 0.2 | 2.5 | 0.7 | 7.5 | 1.2 | 13 |
| Serum 7 | 31.7 | 0.7 | 2.3 | 0.7 | 2.3 | 1.6 | 5.1 |
| Serum 6 | 33.2 | 0.9 | 2.6 | 0.7 | 2.2 | 1.9 | 5.7 |
| Serum 9 | 41 | 1.3 | 3.3 | 0.2 | 0.5 | 1.9 | 4.5 |
| Serum 1 | 44.2 | 1.3 | 2.8 | 0.0 | 0.0 | 1.9 | 4.2 |
| Serum 10 | 96 | 2.4 | 2.5 | 1.4 | 1.5 | 3.8 | 3.9 |
| Control 1 | 99 | 2.5 | 2.5 | 0.8 | 0.8 | 3.5 | 3.5 |
| Serum 2 | 243 | 5.5 | 2.3 | 5.2 | 2.1 | 9.7 | 4 |
| Serum 3 | 531 | 10.8 | 2.0 | 8.7 | 1.6 | 18.6 | 3.5 |
| Control 2 | 970 | 21.1 | 2.2 | 13.5 | 1.4 | 34.5 | 3.6 |
| Serum 5 | 4913 | 56.5 | 1.2 | 186.0 | 3.8 | 239.0 | 4.9 |
| Serum 8 | 8826 | 110.0 | 1.3 | 350.0 | 4.0 | 447.0 | 5.1 |
sFlt-1/PlGF Ratio
| Sample | Mean | Repeatability | | Between-day | | Within-site | |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | SD | %CV | SD | %CV | SD | %CV |
| Serum 5 | 0.02 | 0.0005 | 2.2 | 0.0003 | 1.2 | 0.0006 | 2.5 |
| Serum 8 | 0.2 | 0.004 | 1.9 | 0.002 | 0.8 | 0.005 | 2.0 |
| Control 2 | 1.1 | 0.02 | 1.5 | 0.0 | 0.0 | 0.02 | 1.5 |
| Control 1 | 1.1 | 0.03 | 2.5 | 0.003 | 0.3 | 0.03 | 2.5 |
| Serum 3 | 6.5 | 0.1 | 1.7 | 0.04 | 0.6 | 0.1 | 1.8 |
| Serum 2 | 9.0 | 0.1 | 1.6 | 0.1 | 0.7 | 0.2 | 1.7 |
| Serum 4 | 10.2 | 0.9 | 9.1 | 0.4 | 3.6 | 1.0 | 9.8 |
| Serum 1 | 45.6 | 1.2 | 2.6 | 0.5 | 1.1 | 1.3 | 2.8 |
| Serum 9 | 50.7 | 1.4 | 2.8 | 0.5 | 1.0 | 1.5 | 3.0 |
| Serum 10 | 183 | 4.4 | 2.4 | 0.0 | 0.0 | 4.4 | 2.4 |
| Serum 6 | 850 | 41.5 | 4.9 | 11.3 | 1.3 | 43.0 | 5.1 |
| Serum 7 | 2338 | 110.0 | 4.7 | 55.5 | 2.4 | 123.0 | 5.3 |
| Sample | Mean | Between-lot | | Between-site | | Reproducibility | |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | SD | %CV | SD | %CV | SD | %CV |
| Serum 5 | 0.02 | 0.0004 | 1.6 | 0.0008 | 3.4 | 0.001 | 4.5 |
| Serum 8 | 0.2 | 0.004 | 1.8 | 0.005 | 2.3 | 0.08 | 3.5 |
| Control 2 | 1.1 | 0.02 | 1.8 | 0.01 | 1.0 | 0.03 | 2.6 |
| Control 1 | 1.1 | 0.02 | 1.4 | 0.02 | 1.5 | 0.04 | 3.2 |
| Serum 3 | 6.5 | 0.2 | 2.4 | 0.1 | 1.0 | 0.2 | 3.2 |
| Serum 2 | 9.0 | 0.2 | 2.3 | 0.1 | 0.6 | 0.3 | 3.0 |
| Serum 4 | 10.2 | 0.0 | 0.0 | 0.8 | 8.2 | 1.3 | 12.7 |
| Serum 1 | 45.6 | 1.4 | 3.0 | 0.5 | 1.2 | 1.9 | 4.2 |
| Serum 9 | 50.7 | 1.4 | 2.8 | 0.4 | 0.8 | 2.1 | 4.2 |
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| Serum 10 | 183 | 6.4 | 3.5 | 0.1 | 0.1 | 7.7 | 4.2 |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Serum 6 | 850 | 21.8 | 2.6 | 20.4 | 2.4 | 52.4 | 6.2 |
| Serum 7 | 2338 | 71.0 | 3.0 | 81.9 | 3.5 | 164.0 | 7.0 |
2. Linearity:
The linearity performance of the Elecsys sFlt-1 and Elecsys PlGF assays was established following the recommendations in the CLSI guideline EP06-Ed2.
sFlt-1
In the study, eleven separate panels that together cover the full measuring range were evaluated. The high concentration sample for each panel consisted of native human serum samples or samples spiked with recombinant sFlt-1 antigen. Known volumes of each respective high concentration sample in the panel were mixed with a low concentration sample to prepare different levels for linearity testing. For each linearity panel, the samples were measured in four replicates with one lot of reagent kit using one instrument. The results for each linearity panel were analyzed by weighted linear regression with an intercept; with expected concentrations based on the dilutions on the x-axis and average observed concentration on the y-axis. At each concentration, the deviation from linearity was calculated based on the difference between the observed concentration and the predicted concentration. The deviation from linearity at each level supports that the assay is linear across the claimed sFlt-1 measuring range of 80 to 85,000 pg/mL.
PlGF
In the study, three separate panels that cover the full measuring range were evaluated. The high concentration sample for each panel consisted of human serum samples spiked with a mixture of PlGF-1/PlGF-2. Known volumes of each respective high concentration sample in the panel were mixed with a low concentration sample to prepare different levels for linearity testing. For each linearity panel, the samples were measured in four replicates with one of reagent kit using one instrument. The results for each linearity panel were analyzed by weighted linear regression with an intercept; with expected concentrations based on the dilutions on the x-axis and average observed concentration on the y-axis. At each concentration, the deviation from linearity was calculated based on the difference between the observed concentration and the predicted concentration. The deviation from linearity at each level supports that the assay is linear across the claimed PlGF measuring range of 10 to 5400 pg/mL.
3. Analytical Specificity/Interference:
Endogenous substances
Endogenous interference testing was conducted based on recommendations in CLSI EP07-3rd edition. Potential endogenous interferents or equivalent amounts of solvent were spiked into 4 native human serum sample pools from pregnant women containing different concentrations of sFlt-1 and PlGF covering different analytes ratios. Testing was conducted in replicates of five on one cobas e 411 analyzer. The data showed that the % interference for endogenous substances was within ±10% for both sFlt-1 and PlGF.
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| Interfering Substance | Highest concentration of interferent tested that did not show significant interference |
| --- | --- |
| Biotin | 1200 ng/mL |
| Bilirubin | 26.4 mg/dL |
| Hemoglobin | 1100 mg/dL |
| Intralipid (Lipemia) | 2200 mg/dL |
| Rheumatic Factor | 1320 IU/mL |
## Exogenous substances
Potential exogenous interferents or equivalent amounts of solvent were spiked into serum sample pools containing approximately 100 pg/mL sFlt-1 and 20 pg/mL PlGF, 5000 pg/mL sFlt-1 and 80 pg/mL PlGF, or 5000 pg/mL sFlt-1 and 130 pg/mL PlGF. Four additional drugs prescribed to treat hypertension and prevent seizures in pregnant women (Magnesium Sulfate, alpha-Methyldopa, Nifedipine, Labetalol) were also tested for potential interference using four different serum pools collected from the pregnant women covering the measuring ranges and containing a ratio close to the cut-off. For all substances, testing was conducted in replicates of five on one cobas e 411 analyzer. The data showed that the % interference for exogenous substances was within ± 10% for both sFlt-1 and PlGF.
| Interfering Substance | Highest concentration of interferent tested that did not show significant interference (mg/L) |
| --- | --- |
| Acetaminophen | 260 |
| Acetyl cysteine | 150 |
| Acetylsalicylic acid | 1000 |
| Albumin | 60000 |
| Ampicillin - Na | 1000 |
| Ascorbic acid | 300 |
| Caffeine | 59 |
| Calcium | 200 |
| Cefoxitin | 2500 |
| Cyclosporine | 5 |
| Dihydralazin | 200 |
| Doxycycline | 50 |
| Ethanol | 5% (v/v) |
| Folic acid | 2.4 |
| Gentamicin | 10 |
| Heparin* | 5000 U/L (sFlt-1), 500 U/L (PlGF) |
| Ibuprofen | 500 |
| Iron | 72 |
| Levodopa | 20 |
| Metronidazole | 200 |
| Metroprolol | 5 |
| Phenylbutazone | 400 |
| Rifampicin | 60 |
| Theophylline | 100 |
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| Magnesium Sulfate | 252 |
| --- | --- |
| Alpha-Methyldopa | 1800 |
| Nifedipine | 72 |
| Labetalol | 1400 |
* The labeling contains the following limitation:
"Due to interference of heparin > 500 U/L with Elecsys PlGF, the sFlt-1/PlGF assay should not be used in pregnant women receiving heparin within 36 hours after heparin administration."
## Human Anti-Mouse Antibodies (HAMA)
The effect on quantitation of analyte in the presence of human anti-mouse antibodies (HAMA) using the Elecsys sFlt-1 and Elecsys PlGF assays was determined on the cobas e411 analyzer using human serum sample pools from pregnant women. Four different human serum sample pools from pregnant women containing different concentrations of sFlt-1, PlGF, and sFlt-1/PlGF ratios were tested in duplicate with HAMA spiked at a concentration of 81 µg/L.
| sFlt-1 (pg/mL) | Deviation | PlGF (pg/mL) | Deviation | Ratio | Deviation |
| --- | --- | --- | --- | --- | --- |
| 95.2 | 162 pg/mL | 11.6 | 2 % | 8.24 | 156% |
| 3624 | 5 % | 91 | -5 % | 39.8 | 12 % |
| 7919 | 4 % | 316 | -5 % | 25.1 | 10 % |
| 2190 | 8 % | 1155 | -5 % | 2.16 | 14 % |
No interference was observed for the Elecsys PlGF assay. Significant positive deviation from the reference sample was observed for the Elecsys sFlt-1 assay at analyte concentrations ≤ 2190 pg/mL.
The labeling contains the following limitation:
"Heterophilic human anti-mouse antibodies (HAMA) interference was tested up to a HAMA concentration of 81 µg/L. No HAMA interference for Elecsys PlGF was found. For sFlt-1 concentrations ≤ 2190 pg/mL, the HAMA was shown to interfere, resulting in sFlt-1/PlGF ratios ≥ 10 % deviation with a positive bias.
## Interference from potential cross-reactive substances
A pooled human serum from pregnant women with sFlt-1 ~5000 pg/mL, PlGF ~ 130 pg/mL (sFlt-1/PlGF ratio ~38) was prepared and divided into two aliquots as the test sample (with added substance) and the control sample (with no added substance). Sample testing was conducted with one lot of reagent kit for each analyte with five replicates on one cobas e 411 analyzer. For each substance, the results were analyzed to identify the highest concentration of that substance that did not show significant interference. The results are summarized below.
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sFlt-1
| Substance | Highest concentration of interferent tested that did not show significant interference |
| --- | --- |
| VEGF 165 | 2750 pg/mL |
| VEGF-B | 10000 pg/mL |
| VEGF/PlGF-1 | 10000 pg/mL |
| VEGFR2 | 11 μg/mL |
| VEGFR3 | 1.43 μg/mL |
| PlGF-2 | 5000 pg/mL |
PlGF
| Substance | Highest concentration of interferent tested that did not show significant interference |
| --- | --- |
| VEGF 165 | 10000 pg/mL |
| VEGF-B | 10000 pg/mL |
| VEGF/PlGF-1 | 2750 pg/mL |
| VEGFR2 | 11 μg/mL |
| VEGFR3 | 1.43 μg/mL |
sFlt-1/PlGF Ratio
| Interfering substance | Highest concentration of interferent tested that did not show significant interference |
| --- | --- |
| VEGF 165 | 10000 pg/mL |
| VEGF-B | 10000 pg/mL |
| VEGF/PlGF-1 | 5500 pg/mL |
| VEGFR2 | 11 μg/mL |
| VEGFR3 | 1.43 μg/mL |
Cross-reactivity
sFlt-1
A study was conducted to evaluate the Elecsys sFlt-1 assay on the cobas e411 analyzer for potential cross-reactivity to VEGFR2, VEGFR3, and VEGF-B. Native serum pools with sFlt-1 concentrations of ~1300 and ~9000 pg/mL or ~5000 pg/mL were spiked with the potential cross-reactants. Results from these spiked serum samples were compared to unspiked reference samples and the % cross-reactivity was calculated using the following formula:
$$
\% \text{ cross-reactivity} = (\text{mean of spiked sample} - \text{mean of unspiked sample}) / \text{spiked concentration of cross-reactant} \times 100
$$
Results are shown below.
| Substance | Substance Concentration | Test sample average sFlt-1, pg/mL | Control sample average sFlt-1, pg/mL | % Cross-Reactivity |
| --- | --- | --- | --- | --- |
| VEGFR2 | 11,000,000 pg/mL | 1342 | 1283 | 0.0005% |
| | | 9790 | 9556 | 0.002% |
| VEGFR3 | 1,430,000 pg/mL | 1298 | 1279 | 0.001% |
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| | | 9725 | 9565 | 0.011% |
| --- | --- | --- | --- | --- |
| VEGF-B | 10,000 pg/mL | 5215 | 5012 | 2.03% |
## PIGF
A study was conducted to evaluate the Elecsys sFlt-1 assay on the cobas e411 analyzer for potential cross-reactivity to VEGF165, VEGF-B, PIGF-2, PIGF-1/VEGF heterodimer. Native serum pools with PIGF concentrations of ~ 65 and ~180 pg/mL or ~130 pg/mL were spiked with the potential cross-reactants. Results from these spiked serum samples were compared to unspiked reference samples and the % cross-reactivity was calculated using the following formula:
$$
\% \text{ cross-reactivity} = (\text{mean of spiked sample} - \text{mean of unspiked sample}) / \text{spiked concentration of cross-reactant} \times 100
$$
Results are shown below.
| Substance | Substance Concentration | Test sample average PIGF, pg/mL | Control sample average PIGF, pg/mL | % Cross-reactivity |
| --- | --- | --- | --- | --- |
| VEFG165 | 44,000 pg/mL | 83 | 57 | 0.058% |
| | | 215 | 204 | 0.024% |
| PlGF-2 | 2750 pg/mL | 728 | 61 | 25% |
| | | 1022 | 204 | 29% |
| | 100 pg/mL | 175 | 133 | 42% |
| PlGF-1/VEGF heterodimer | 44,000 pg/mL | 486 | 60 | 0.968% |
| | | 1075 | 208 | 1.969% |
| VEGF-B | 10,000 pg/mL | 142 | 133 | 0.09% |
The labeling contains the following mitigation:
"Recombinant PIGF-2 protein shows up to 42% cross-reactivity and interferes with the Elecsys PIGF assay. Therefore, caution should be used when interpreting sFlt-1/PlGF assay results in the setting of exogenous recombinant PIGF-2 protein therapeutic use."
## High dose hook effect
Three low analyte serum samples from single donors were spiked with recombinant sFlt-1 or PIGF to achieve high concentrations. For each sample, a dilution series was prepared using human serum which contained low levels of sFlt-1 or low levels of PIGF. No hook effect was seen up to 200,000 pg/mL sFlt-1 and up to 100,000 pg/mL of PIGF.
4. Assay Reportable Range:
The analytical measuring range for the Elecsys sFlt-1 and PIGF assays is 80 to 85,000 pg/mL and 10 to 5,400 pg/mL, respectively.
5. Traceability, Stability, Expected Values (Controls, Calibrators, or Methods):
## Metrological Traceability
The metrological traceability of the Elecsys sFlt-1 and Elecsys PIGF was established following the guidelines in EN ISO 17511:2020 In vitro diagnostic medical devices –
{15}
Requirements for establishing metrological traceability of values assigned to calibrators, trueness control materials and human samples. The calibrators were established using a commercially available reference preparation of sFlt-1 and PlGF that is considered by the sponsor as the highest reference for the assay. The sponsor's detailed metrological traceability for sFlt-1 and PlGF was reviewed and found to be acceptable.
## Specimen Stability
To validate sample stability claims in the labeling, storage conditions at room temperature (15-25°C), refrigerated (2-8°C), frozen (-20 ± 5°C) and various freeze/thaw cycles were tested and compared to results obtained from fresh, never frozen native patient samples. The data support the sample stability for 6 days at 15-25 °C, 15 days at 2-8 °C, 6 months at -20 °C (± 5 °C) and one freeze/thaw cycle.
## 6. Detection Limit:
### Limit of Blank (LoB)
To determine the LoB for the Elecsys sFlt-1 and Elecsys PlGF assays, one analyte-free serum sample was evaluated with three reagent lots for a total of 60 measurements per reagent lot. Testing was conducted on one cobas e411 analyzer, six runs over three days with ten replicates per run. The LoB was determined for each lot using the non-parametric approach described in CLSI EP17-A2. The LoB was determined as the 95th percentile of measurements of blank samples.
### Limit of Detection (LoD)
To determine the LoD for the Elecsys sFlt-1 and PlGF assays, five low-analyte serum samples were assayed with three reagent lots for a total of 60 measurements per reagent lot. Testing was conducted in six runs over three days with two replicates per run on one cobas e411 analyzer. The LoD was determined for each lot as described in CLSI EP17-A2 using the following equation:
$$
\mathrm{LoD} = \mathrm{LoB} + 1.653 \times \mathrm{SD}_{\text{total}}
$$
### Limit of Quantitation (LoQ)
To determine the LoQ for the Elecsys sFlt-1 and PlGF assays, four low-analyte serum samples were measured in replicates of five, one run per day over five days on one cobas e411 analyzer using three reagent lots. For each lot, the LoQ was defined as the mean concentration of the lowest sample which could be quantified with an intermediate precision of no more than 20% CV.
The LoB, LoD, and LoQ studies support the following labeling claims:
| Analyte | LoB | LoD | LoQ |
| --- | --- | --- | --- |
| sFlt-1 (pg/mL) | 6 | 10 | 15 |
| PlGF (pg/mL) | 2 | 3 | 10 |
## 7. Assay Cut-Off:
The measuring range for the Elecsys sFlt-1 and PlGF assays is determined by the linearity experiments, precision/reproducibility, and the clinical studies.
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# B Comparison Studies:
1. Method Comparison with Predicate Device:
Not Applicable: see clinical studies in Section VII.C.
2. Matrix Comparison:
Not Applicable.
# C Clinical Studies:
1. Clinical Sensitivity:
The clinical performance of the Elecsys sFlt-1/PlGF ratio was evaluated on the cobas e411 analyzer using serum samples from the clinical study titled PRAECIS: Preeclampsia Risk Assessment: Evaluation of Cut-offs to Improve Stratification. Identification and Validation of a Cut-off for the Ratio of Soluble Fms-like Tyrosine Kinase-1 to Placental Growth Factor (sFlt-1/PlGF) to Stratify Risk in Pregnant Women with Hypertensive Disorders of Pregnancy.
The study was a prospective, multicenter, blinded, non-interventional study conducted across 18 sites in the United States. Women with singleton pregnancies between 23+0 and 34+6/7 weeks gestation who were hospitalized (or being hospitalized) for a hypertensive disorder of pregnancy were enrolled. Hypertensive disorders included: preeclampsia (PE), chronic hypertension (HTN) with or without superimposed PE or gestational hypertension, as defined by American College of Obstetricians and Gynecologists (ACOG) 2013 guidelines (Hypertension in Pregnancy. Obstet Gynecol. 2013 Nov;122(5):1122-31.) and the 2019 update (Chronic Hypertension in Pregnancy, OBSTETRICS & GYNECOLOGY, VOL. 133, NO. 1, JANUARY 2019). Women who met the criteria for PE with severe features (sPE) at the time of enrollment were excluded. Women who met the following criteria were also not eligible for the study: withdrew patient consent, multiple fetus pregnancy, outside the gestational age range, or delivered before specimens could be collected. Patients with multiple hospitalizations were not excluded; 34 patients were enrolled twice; one patient was enrolled three times. The study population comprised 556 enrollments of 520 patients of the following races:
| Race | % (n) |
| --- | --- |
| American Indian or Alaskan Native | 0.38 (2) |
| Asian | 5.96 (31) |
| Black/African American | 29.62 (154) |
| Hawaii or Other Pacific Islanders | 0.58 (3) |
| Other | 4.23 (22) |
| Unknown or Undeclared | 5.19 (27) |
| While/Caucasian | 54.04 (281) |
For each patient enrolled into the study, serum samples were collected for determination of sFlt-1 and PlGF levels at baseline, and derivation of the sFlt-1/PlGF ratio. The samples were stored frozen (-70°C) and sent to a central laboratory for later testing as a batch. Information
{17}
about sample stability was provided to support the use of frozen samples to demonstrate clinical performance.
All women enrolled in the study were followed for two weeks or until delivery within two weeks. The development of sPE within a two-week window of enrollment was the study endpoint/clinical outcome. A central adjudication committee (panel of 3 independent obstetricians) was assembled to review data and arrive at consensus regarding each patient's diagnoses for the development of sPE following the 2013 ACOG clinical practice guidelines. The measured results were compared to the external clinical adjudication result.
The interpretation of results of the device based on the sFlt-1/PlGF ratio for progression to preeclampsia with severe features within 2 weeks were as follows:
High risk if sFlt-1/PlGF ratio > 38
Low risk if sFlt-1/PlGF ratio ≤ 38
The severe preeclampsia status per adjudication panel and device results were analyzed based on the number of enrollments (n=556). The results are shown below.
| | | Severe preeclampsia status | | |
| --- | --- | --- | --- | --- |
| | | Yes | No | Total |
| SFlt-1/PlGF | Ratio > 38 | 170
True positive | 84
False positive | 254 |
| | Ratio ≤ 38 | 16
False negative | 286
True negative | 302 |
| | Sum | 186 | 370 | 556 |
Prevalence for developing sPE within two weeks in the clinical study = 33% (186/556). Of the 556 results, there were 84 false positives and 16 false negatives.
The positive predictive value (PPV) and negative predictive value (NPV) are summarized below:
| PPV (95% CI) | NPV (95% CI) |
| --- | --- |
| 66.9 % (60.8, 72.7) | 94.7% (91.5, 96.9) |
The positive likelihood ratio (PLR) and negative likelihood ratio (NLR) are summarized below:
| PLR (95% CI) | NLR (95% CI) |
| --- | --- |
| 4.03 (3.32, 4.88) | 0.11 (0.07, 0.18) |
The sensitivity and specificity are summarized below:
| Sensitivity (95% CI) | Specificity (95% CI) |
| --- | --- |
| 91.4 % (86.4, 95.0) | 77.3 % (72.7, 81.5) |
The clinical results were stratified into subgroups based on the four hypertensive disorders of pregnancy, gestation age (<30 weeks and ≥ 30 weeks), and maternal age (18-34 years and 35-50 years). There was no significant difference in clinical performance across the hypertensive disorders of pregnancy, gestation age, or maternal age.
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2. Clinical Specificity:
See section C.1.
3. Other Clinical Supportive Data (When 1. and 2. Are Not Applicable):
See section C.1.
D Clinical Cut-Off:
See Section C.1.
E Expected Values/Reference Range:
In a population of 380 healthy pregnant women between week 23+0 up to week 34+6 gestation, the sFlt-1/PlGF ratio median was established at 3.2, the 2.5th percentile at 0.9 and the 97.5% percentile at 13.5.
VIII Proposed Labeling:
The labeling supports the finding of substantial equivalence for this device.
IX Conclusion:
The submitted information in this premarket notification is complete and supports a substantial equivalence decision.
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