ELECSYS RUBELLA IGM IMMUNOASSAY
Device Facts
| Record ID | K092322 |
|---|---|
| Device Name | ELECSYS RUBELLA IGM IMMUNOASSAY |
| Applicant | Roche Diagnostics |
| Product Code | LFX · Microbiology |
| Decision Date | Mar 12, 2010 |
| Decision | SESE |
| Submission Type | Traditional |
| Regulation | 21 CFR 866.3510 |
| Device Class | Class 2 |
Indications for Use
The Elecsys Rubella IgM immunoassay is for the in vitro qualitative determination of IgM antibodies to rubella virus in human serum and Li-heparin, K₃-EDTA and sodium citrate plasma. This assay may be used as an aid in the presumptive diagnosis of an acute or recent rubella infection, including women of childbearing age. The electrochemiluminescence immunoassay “ECLIA” is intended for use on Elecsys and cobas e immunoassay analyzers. The Elecsys PreciControl Rubella IgM is used for quality control of the Elecsys Rubella IgM immunoassay on the Elecsys and cobas e immunoassay analyzers.
Device Story
The Elecsys Rubella IgM immunoassay is an automated, in vitro diagnostic test for detecting IgM antibodies to rubella virus in human serum or plasma. The device uses an electrochemiluminescence immunoassay (ECLIA) principle. Patient samples are incubated with biotinylated monoclonal anti-human IgM antibodies and rubella-specific recombinant antigens. Ruthenium-labeled rubella-specific antibodies and streptavidin-coated microparticles are added to form a sandwich complex. The reaction mixture is aspirated into a measuring cell where microparticles are magnetically captured on an electrode. Voltage application induces chemiluminescent emission, measured by a photomultiplier. Results are calculated as a Cut-off Index (COI) using a 2-point calibration curve. The device is intended for use on Roche Elecsys and cobas e immunoassay analyzers in clinical laboratory settings. It aids clinicians in diagnosing acute or recent rubella infection. The system includes quality control materials (PreciControl Rubella IgM) to ensure assay performance. The device provides qualitative results (non-reactive, indeterminate, or reactive) to support clinical decision-making.
Clinical Evidence
Method comparison study performed against predicate devices (Zeus Scientific, Abbott AxSym, DPC Immulite). Results for pregnant subjects showed 99.20% negative agreement (131/132) and 0% positive agreement (0/0). Non-pregnant subjects showed 98.90% negative agreement (364/368) and 0% positive agreement (0/1). Precision studies reported intra-assay CVs of 1.03-6.71% and inter-assay CVs of 1.86-17.07% for plasma samples.
Technological Characteristics
Two-step sandwich immunoassay; electrochemiluminescence (ECLIA) detection; streptavidin microparticles; ruthenium-labeled antibodies. Automated platform (Elecsys/cobas e analyzers). Calibrators included in kit. Matrix: human serum, Li-heparin, K3-EDTA, sodium citrate plasma.
Indications for Use
Indicated for the qualitative detection of IgM antibodies to rubella virus in human serum and plasma (Li-heparin, K3-EDTA, sodium citrate) to aid in the presumptive diagnosis of acute or recent rubella infection, particularly in women of childbearing age.
Regulatory Classification
Identification
Rubella virus serological reagents are devices that consist of antigens and antisera used in serological tests to identify antibodies to rubella virus in serum. The identification aids in the diagnosis of rubella (German measles) or confirmation of a person's immune status from past infections or immunizations and provides epidemiological information on German measles. Newborns infected in the uterus with rubella virus may be born with multiple congenital defects (rubella syndrome).
Special Controls
*Classification.* Class II. The special controls for this device are:(1) National Committee for Clinical Laboratory Standards': (i) 1/LA6 “Detection and Quantitation of Rubella IgG Antibody: Evaluation and Performance Criteria for Multiple Component Test Products, Speciment Handling, and Use of the Test Products in the Clinical Laboratory, October 1997,” (ii) 1/LA18 “Specifications for Immunological Testing for Infectious Diseases, December 1994,” (iii) D13 “Agglutination Characteristics, Methodology, Limitations, and Clinical Validation, October 1993,” (iv) EP5 “Evaluation of Precision Performance of Clinical Chemistry Devices, February 1999,” and (v) EP10 “Preliminary Evaluation of the Linearity of Quantitive Clinical Laboratory Methods, May 1998,” (2) Centers for Disease Control's: (i) Low Titer Rubella Standard, (ii) Reference Panel of Well Characterized Rubella Sera, and (3) World Health Organization's International Rubella Standard.
Predicate Devices
Related Devices
- K072617 — ELECSYS RUBELLA IGG IMMUNOASSAY · Roche Diagnostics Corp. · Dec 5, 2008
- K122397 — LIAISON RUBELLA IGM, LIAISON CONTROL RUBELLA IGM · DiaSorin, Inc. · Sep 6, 2012
- K012077 — IMMULITE RUBELLA IGM,LKRM1, LKRM2, IMMULITE 2000 RUBELLA IGM, MODEL L2KRM2, L2KRM6 · Diagnostic Products Corp. · Jan 10, 2002
Submission Summary (Full Text)
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510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION
DECISION SUMMARY
A. 510(k) Number: k092322
B. Purpose for Submission: Clearance of new device
C. Measurand: Rubella-specific IgM in human serum and plasma
D. Type of Test: Electrochemiluminescence immunoassay (ECLIA)
E. Applicant: Roche Diagnostics
F. Proprietary and Established Names: Elecsys Rubella IgM immunoassay
Elecsys PreciControl Rubella IgM
G. Regulatory Information:
1. Regulation section: 21 CFR §866.3510, Rubella virus serological reagents
21 CFR §862.1660, Quality control material
2. Classification: Class II
3. Product code: LFX (Enzyme Linked Immunoabsorbent Assay, Rubella)
JJX (Quality control material, assayed and unassayed)
4. Panel: Virology (81)
H. Intended Use:
1. Intended use(s):
The Elecsys Rubella IgM immunoassay is for the in vitro qualitative determination of IgM antibodies to rubella virus in human serum and Li-heparin, K₃-EDTA and sodium citrate plasma. This assay may be used as an aid in the presumptive diagnosis of an acute or recent rubella infection, including women of childbearing age.
The electrochemiluminescence immunoassay “ECLIA” is intended for use on Elecsys and cobas e immunoassay analyzers.
The Elecsys PreciControl Rubella IgM is used for quality control of the Elecsys Rubella IgM immunoassay on the Elecsys and cobas e immunoassay analyzers.
NOTE: This assay has not been cleared/approved by the FDA for blood/plasma donor screening.
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2. **Indication(s) for use:**
The Elecsys Rubella IgM assay may be used as an aid in the presumptive diagnosis of an acute or recent rubella infection, including in women of childbearing age.
3. **Special conditions for use statement(s):**
For prescription use only
4. **Special instrument requirements:**
Previously cleared with: K961481 (Elecsys 2010 and E170); K060373 (cobas e601). Inclusion of the cobas e analyzers in the labeling has been accepted previously for K072617 and K073501 after review by FDA on Dec. 10, 2008.
I. **Device Description:**
Samples are incubated with biotinylated monoclonal anti-human IgM-specific antibodies and rubella-specific recombinant antigens, forming a complex with the anti-rubella IgM antibodies present in the sample. The addition of ruthenium-labeled rubella specific antibodies and streptavidin-coated microparticles forms a sandwich complex via biotin-streptavidin interaction. The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode, and unbound substances are then removed with ProCell. Voltage application to the electrode induces chemiluminescent emission, which is then measured by a photomultiplier. Results are determined via a calibration curve generated by 2-point calibration and a master curve provided via the reagent barcode.
J. **Substantial Equivalence Information:**
1. **Predicate device name(s):** K984180, Zeus Scientific Rubella IgM ELISA Test System.
Additional predicates for a two out of three consensus (routine and supplemental positive cohorts): Abbott Labs. AxSYM Rubella IgM Antibody Assay (K954318) and DPC Immulite IgM (K012077)
2. **Comparison with main predicate:**
| Similarities | | |
| --- | --- | --- |
| Item | Device | Main Predicate |
| Intended Use | The Elecsys Rubella IgM immunoassay is for the in vitro qualitative determination of IgM antibodies to rubella virus in human serum and Li-heparin, K_{3}- | The Zeus Scientific, Inc. Laboratories Rubella IgM ELISA Test System is designed for the qualitative detection of IgM antibodies to rubella virus in |
| | human serum and Li-heparin, K_{3}- | antigen, and the anti-rubella IgM antibodies are used for the quantitative detection of IgM antibodies to rubella virus in human serum and Li-heparin, K_{3}- |
| Intended Use | Rubella IgM immunoassay is for the in vitro quantitative determination of IgM antibodies to rubella virus in human serum and Li-heparin, K_{3}- | Rubella IgM ELISA Test System is designed for the quantitative detection of IgM antibodies to rubella virus in human serum and Li-heparin, K_{3}- |
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| Similarities | | |
| --- | --- | --- |
| Item | Device | Main Predicate |
| | EDTA and sodium citrate plasma. This assay may be used as an aid in the presumptive diagnosis of an acute or recent rubella infection, particularly in women of childbearing age. The electrochemiluminescence immunoassay “ECLIA” is intended for use on Elecsys and cobas e immunoassay analyzers. | human serum. The test system is intended to be used to evaluate serological evidence of acute or recent infection with rubella virus and is for in vitro diagnostic use. |
| Indications for Use | Aid in the presumptive diagnosis of an acute or recent rubella infection, particularly in women of childbearing age. | Intended to be used to evaluate serological evidence of acute or recent infection with rubella virus. |
| Unit of Measure | COI (S/CO) | COI (S/CO) |
| Calibrator | Included in kit | Included in kit |
| Differences | | |
| Item | Device | Predicate |
| Sample Type | Human serum, lithium heparin plasma, potassium EDTA plasma, and sodium citrate plasma. | Serum. |
| Assay Technique | Electrochemiluminescent immunoassay | ELISA |
| Instrument Platform | Automated. Roche Elecsys 2010 and Modular Analytics E170 (Elecsys module) and cobas e immunoassay analyzers. | No automated instrument platform. ELISA equipment/microwell plate reader needed. No specific model required. |
| Cut-off | Neg: <0.8 Pos: ≥ 1.0 (S/CO) | Neg: ≤ 0.9 Pos: ≥ 1.10 (S/CO) |
| Equivocal Zone | 0.8 to1.0 (S/CO) | 0.91 to 1.09 (S/CO) |
| Calibrator levels | Two | One |
| Calibration frequency | Once per reagent lot and - After 1 month when using same reagent lot - After 7 days when using same reagent kit - As required per QC findings or pertinent regulations | Each time the assay is run. |
| Controls | PreciControl Rubella IgM (sold separately) | Positive and negative control included in kit. |
# K. Standard/Guidance Document Referenced (if applicable):
CLSI EP5-A2, "Evaluation of Precision Performance of Quantitative Measurement Methods"
CLSI EP17-A, "Protocols for Determination of Limits of Detection"
# L. Test Principle:
The Elecsys Rubella IgM Immunoassay is a two-step sandwich immunoassay with
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streptavidin microparticles and electrochemiluminescence detection. The Rubella IgM is composed of a biotin-labeled monoclonal antibody against human IgM, a Rubella-like particle and a ruthenium-labeled anti-Rubella antibody. A relationship exists between the concentration of the IgM antibody targets present in a patient sample and the level of signal count detected by the system. The IgM assay is a qualitative test based on a cut-off formula dependent on the negative and positive calibrators. Cut-off index (COI) is based on the ratio of assay signal to cut-off signal (also abbreviated s/co). COI values equal to or greater than 1.0 are considered positive for the presence of anti-Rubella IgM antibody. Results are determined using a 2 point calibration. The test system contains the human serum-based calibrators intended for use with the system. The Elecsys Precicontrol Rubella IgM contains two levels of human serum. The positive control contains native, inactivated Rubella IgM antibodies.
The Elecsys PreciControl Rubella IgM contains two levels of human serum. The positive control contains native, inactivated Rubella IgM antibodies.
# M. Performance Characteristics (if/when applicable):
# 1. Analytical performance:
# a. Precision/Reproducibility:
Reproducibility was determined at three different external sites (Site A, B, and C) using Elecsys reagents, human sera, and controls in a modified protocol (EP5-A2) of the CLSI (Clinical and Laboratory Standards Institute): 6 times daily for 10 days $(n = 60)$ . Precision was determined at one internal site (Site D), where the samples were run 20 times for repeatability and tested twice a day for 10 days $(n = 100)$ for intermediate precision. Note that the site C intermediate precision $\% \mathrm{CV}$ values (using the Elecsys 2010 and cobas e 411 analyzer) are significantly higher than those from sites A and B (using the Modular Analytics E170 and cobas e 601). The following results were obtained:
| Site A | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| MODULAR ANALYTICS E170 and cobas e 601 analyzers | | | | | | |
| | | | Repeatabilityb | | Intermediate precisionc | |
| Sample | N | Mean S/CO | SD S/CO | CV % | SD S/CO | CV % |
| PCd Rubella IgM 1 | 59 | 0.24 | 0.006 | 2.70 | 0.009 | 3.89 |
| PC Rubella IgM 2 | 59 | 1.77 | 0.085 | 4.83 | 0.098 | 5.57 |
| Serum Pool 1 | 58 | 0.23 | 0.003 | 1.43 | 0.006 | 2.86 |
| Serum Pool 2 | 58 | 1.87 | 0.041 | 2.18 | 0.056 | 3.00 |
| Serum Pool 3 | 58 | 6.21 | 0.125 | 2.01 | 0.208 | 3.35 |
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b) repeatability = within-run precision c) intermediate precision = total precision (includes inter-assay precision) d) PC = PreciControl
| Site B | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| MODULAR ANALYTICS E170 and cobas e 601 analyzers | | | | | | |
| | | | Repeatability | | Intermediate precision | |
| Sample | N | Mean S/CO | SD S/CO | CV % | SD S/CO | CV % |
| PC Rubella IgM 1 | 60 | 0.23 | 0.004 | 1.75 | 0.005 | 2.04 |
| PC Rubella IgM 2 | 60 | 1.68 | 0.041 | 2.46 | 0.047 | 2.77 |
| Serum Pool 1 | 60 | 0.22 | 0.003 | 1.54 | 0.004 | 1.72 |
| Serum Pool 2 | 60 | 1.88 | 0.036 | 1.94 | 0.047 | 2.49 |
| Serum Pool 3 | 60 | 6.47 | 0.122 | 1.89 | 0.178 | 2.75 |
| Li-Heparin Plasma Pool 1 | 60 | 0.24 | 0.004 | 1.54 | 0.004 | 1.54 |
| Li-Heparin Plasma Pool 2 | 60 | 1.90 | 0.029 | 1.53 | 0.046 | 2.42 |
| K3-EDTA Plasma Pool 1 | 60 | 0.26 | 0.004 | 1.46 | 0.005 | 1.78 |
| K3-EDTA Plasma Pool 2 | 60 | 1.90 | 0.030 | 1.60 | 0.045 | 2.36 |
| Site C | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| Elecsys 2010 and cobas 411 analyzers | | | | | | |
| | | | Repeatability | | Intermediate precision | |
| Sample | N | Mean S/CO | SD S/CO | CV % | SD S/CO | CV % |
| PC Rubella IgM 1 | 60 | 0.22 | 0.013 | 5.74 | 0.023 | 10.5 |
| PC Rubella IgM 2 | 60 | 2.00 | 0.077 | 3.86 | 0.209 | 10.4 |
| Serum Pool 1 | 60 | 0.21 | 0.007 | 3.11 | 0.020 | 9.53 |
| Serum Pool 2 | 60 | 1.59 | 0.107 | 6.71 | 0.272 | 17.1 |
| Serum Pool 3 | 60 | 6.39 | 0.277 | 4.34 | 0.694 | 10.9 |
| Li-Heparin Plasma Pool 1 | 60 | 0.23 | 0.008 | 3.22 | 0.022 | 9.60 |
| Li-Heparin Plasma Pool 2 | 60 | 2.00 | 0.079 | 3.96 | 0.183 | 9.14 |
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| K3-EDTA Plasma Pool 1 | 60 | 0.25 | 0.010 | 3.90 | 0.024 | 9.69 |
| --- | --- | --- | --- | --- | --- | --- |
| K3-EDTA Plasma Pool 2 | 60 | 2.01 | 0.056 | 2.79 | 0.172 | 8.59 |
| Site D | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| Elecsys 2010 and cobas e 411 analyzers | | | | | | |
| | Repeatability | | | Intermediate precision | | |
| Sample | Mean COI | SD | CV % | Mean COI | SD | CV % |
| Human Sample 1 | 0.20 | 0.005 | 2.41 | 0.20 | 0.006 | 2.97 |
| Human Sample 2 | 1.29 | 0.016 | 1.23 | 1.31 | 0.024 | 1.86 |
| Human Sample 3 | 3.57 | 0.037 | 1.03 | 6.69 | 0.271 | 4.06 |
| PC Rubella IgM 1 | 0.19 | 0.003 | 1.38 | 0.20 | 0.008 | 4.07 |
| PC Rubella IgM 2 | 1.81 | 0.021 | 1.14 | 1.95 | 0.080 | 4.09 |
Note: the panels used for the precision/reproducibility studies presented here have suboptimal samples regarding the cutoff. Such a panel configuration was acceptable at the time of the original submission. Going forward, newer and current recommendations reflected in published FDA guidelines establish the need for evaluation of samples with values very close to the cutoff (low positive, high negative) for the precision/reproducibility studies. See appropriate FDA guidance documents.
## Quality Control:
Quality control is done using the Elecsys PreciControl Rubella IgM. The controls 1 and 2 should be run as single determinations at least once every 24 hours when the test is in use, once per reagent kit, and after every calibration. The control intervals and limits should be adapted to each laboratory's individual requirements. Results must be within the defined limits. If control values fall outside of the expected range(s), patient results should not be reported and samples and controls should be retested. The recommended quality control material is serum based. The user is responsible for providing alternate control material for plasma samples when necessary. Applicable government regulations and local guidelines for quality control should be followed.
b. Linearity/assay reportable range: N/A
c. Traceability, Stability, Expected values (controls, calibrators, or methods): Traceability:
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This method has been standardized against a Roche standard. The units have been selected arbitrarily.
# Stability:
Reagents:
| unopened at 2-8 °C | up to the stated expiration date |
| --- | --- |
| M, R1, R2 after opening at 2-8 °C | 12 weeks |
| | 2 weeks or |
| on MODULAR ANALYTICS E170, | 12 weeks if stored alternately in the |
| Elecsys 2010 and cobas e | refrigerator and on the analyzers (up to 84 hours) |
| Cal1, Cal2 after opening at 2-8 °C | 8 weeks |
| on Elecsys 2010 and cobas e 411 at 20-25 °C | up to 5 hours |
| on MODULAR ANALYTICS E170 and cobas e 601 | use only once |
Controls:
| unopened at 2-8 °C | up to the stated expiration date |
| --- | --- |
| after opening at 2-8 °C | 8 weeks |
| on the analyzers | up to 5 hours |
# Samples:
The potential influence of frozen human serum samples after storage at $-20\mathrm{C}$ for 3 months was evaluated using recovery of 3 negative, one low positive, and 3 positive samples vs. a fresh reference, and deemed satisfactory.
Similarly, studies of 6 freeze thaw cycles, sample stability for 3 weeks at $4\mathrm{C}$ , and sample stability at $25\mathrm{C}$ for 3 days resulted in satisfactory recovery within the specified acceptance criteria.
# d. Detection limits:
Range for the electrochemiluminescence signals (counts) for the calibrators: Negative calibrator (Cal1): 500-2700 (Elecsys 2010, MODULAR ANALYTICS E170 and cobas e analyzers).
Positive calibrator (Cal2): 5500-30000 (Elecsys 2010, MODULAR ANALYTICS E170 and cobas e analyzers).
The Limit of Blank (LoB) was determined on Elecsys 2010 Immunoassay Analyzer as the $95^{\text{th}}$ percentile of measurements of blank samples. 5 samples were measured 12 times with single determination. The measurements were then ordered according to their values and the $95^{\text{th}}$ percentile was determined, interpolating between the results of $57^{\text{th}}$ and $58^{\text{th}}$ ranked samples as follows: $\mathrm{LoB} = (\mathrm{Conc. Sample} 57 + \mathrm{Conc. Sample} 58)/2$ .
The LoB was: 955 counts (corresponding to concentration of $\sim 54.24\mathrm{U / mL}$ ).
Limit of detection (LoD) was evaluated on Elecsys 2010 Immunoassay Analyzer according to the guidelines of CLSI EP 17-A. The LoD was determined as the lowest amount of Analyte in a sample that can be detected with $95\%$ probability. 5 samples with low concentration were measured 12
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times with single determination; the precision (SD) was calculated for each sample. A pooled estimate of precision over the five samples was then determined $(\mathrm{SD}_{\mathrm{total}})$ . Calculation of the LoD was performed as follows: $\mathrm{LoD} = \mathrm{LoB} + 1.653 \times \mathrm{SD}_{\mathrm{total}}$ .
The resulting LoD was 362 counts (corresponding to a concentration $\sim 61.53$ U/mL)
# e. Analytical specificity:
# Cross-reactivity:
The specificity of the Elecsys Rubella IgM was evaluated by testing a total of 60 specimens representing a variety of disease states (ANA, CMV, EBV, FTA, HBV, HCV, HIV 1/2, HSV, Mumps, Parv B19, RH, VZV). The testing results are summarized in the table below. For all analytical specificity categories tested, $77.6\%$ overall agreement was observed between the Elecsys immunoassay and an FDA-cleared reference method.
| Cross-reactant | N | IgM Elecsys/Comparator Neg/Neg | IgM Elecsys/Comparator Pos/Neg | IgM Elecsys/Comparator Neg/Pos | IgM Elecsys/Comparator Pos/Pos |
| --- | --- | --- | --- | --- | --- |
| ANAc | 3 | 2 | 0 | 1 | 0 |
| CMV | 4 | 1 | 0 | 2 | 1 |
| EBVc | 1 | 0 | 0 | 1 | 0 |
| FTA | 5 | 5 | 0 | 0 | 0 |
| HBVd | 6 | 5 | 0 | 0 | 0 |
| HCV | 5 | 4 | 0 | 1 | 0 |
| HIV 1/2 | 9 | 9 | 0 | 0 | 0 |
| HSV | 8 | 6 | 0 | 2 | 0 |
| Mumpsc | 3 | 3 | 0 | 0 | 0 |
| Parv B19d | 4 | 3 | 0 | 0 | 0 |
| RH | 7 | 3 | 3 | 1 | 0 |
| VZV | 5 | 3 | 0 | 2 | 0 |
| Sub-total | 60 | 44 | 3 | 10 | 1 |
| Total | 60 | 58 | | | |
c) Cross-reactivity not well assessed due to the limited sample size tested.
d) One sample was repeatedly equivocal by the reference method and was excluded from the calculations
# Interference:
The impact of endogenous interfering substances on the Elecsys Rubella IgM Immunoassay was determined testing natural and spiked samples.
Calculations were based on signal-to-cutoff ratio (S/CO). Acceptance criteria was recovery within $+/- 0.25$ S/CO ( $\leq 0.5$ S/CO) or $80 - 120\%$ ( $>0.5$ S/CO), except for Rheumatoid Factor, for which acceptance criterion was concordance rate to predicate device $>90\%$ .
The assay is unaffected by icterus (bilirubin $< 428~\mu \mathrm{mol / L}$ or $< 25~\mathrm{mg / dL}$ ), hemolysis $(\mathrm{Hb} < 1.49~\mathrm{mmol / L}$ or $< 2.4~\mathrm{g / dL})$ , lipemia (Intralipid $< 1500~\mathrm{mg / dL}$ ), Immunoglobulin A up to $9.6~\mathrm{mg / mL}$ , Immunoglobulin G up to $42~\mathrm{mg / mL}$ and biotin $< 205~\mathrm{nmol / L}$ or $< 50~\mathrm{ng / mL}$ . Criterion: Recovery of
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positive samples within ± 20 % of initial value. In patients receiving therapy with high biotin doses (i.e. > 5 mg/day), no sample should be taken until at least 8 hours after the last biotin administration. Rheumatoid factor was not observed to cause any consistent bias, but RF factor levels > 1650 IU/mL may lead to erroneous results in some instances. Elevated levels of unspecific human IgM may cause interference.
In vitro tests were performed on 18 commonly used pharmaceuticals (Acetylcysteine, Ampicillin-Na, Ascorbic acid, Ca-Dobesilate, Ciclosporine, Cefoxitin, Heparin, Intralipid, Levodopa, Methyldopa, Metronidazole, Phenylbutazone, Doxycycline, Acetylsalicylic acid, Rifampicin, Acetaminophen, Ibuprofen, and Theophylline) and in addition on folic acid. No interference with the assay was found.
f. Assay cut-off:
The cutoff for the Elecsys Rubella IgM assay was initially established by measuring 162 positive rubella samples from 18 commercially available seroconversion panels; and 298 negative samples collected from blood donors. The distribution of positive, equivocal and negative results was compared to results from various reference assays and the cutoffs were set as noted below. This setting revealed an excellent separation of negative and positive samples exhibiting only 2 equivocal results out of 460. The resulting cutoff was verified using another reagent kit lot; and was then applied to the performance evaluation studies described below. The result of a sample is given either as reactive or non-reactive as well as in the form of a cutoff index (signal sample/cutoff). Results obtained with the Elecsys Rubella IgM assay can be interpreted as follows:
Non-reactive: < 0.8 COI; Indeterminate: ≥ 0.8 - < 1.0 COI; Reactive: ≥ 1.0 COI
Samples with a cutoff index < 0.8 are non-reactive in the Elecsys Rubella IgM assay. Samples with a cutoff index between ≥ 0.8 and < 1.0 are considered indeterminate. The sample should be retested. In case the result is still indeterminate, a second sample should be collected e.g. within 1 week. A significant increase of the Rubella IgG antibody titer from a first to a second sample supports the diagnosis of acute Rubella infection. Samples with a cutoff index ≥ 1.0 are reactive in the Elecsys Rubella IgM assay.
The magnitude of the measured result above the cutoff is not indicative of the total amount of antibody present in the sample. The anti-Rubella IgM results in a given specimen, as determined by assays from different manufacturers, can vary due to differences in assay and reagent methods.
Calculation
The analyzer automatically calculates the cutoff based on the measurement of Cal1 and Cal2.
2. Comparison studies:
a. Method comparison with predicate device:
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The performance of the Elecsys Rubella IgM assay was determined by percent agreement among negative samples and percent agreement among positive samples, against a consensus comparator method, in specific populations.
For the clinical routine and the banked positive cohorts, a consensus comparator method was defined using a total of three FDA-cleared predicate devices and a two out of three consensus result approach as described in the following table:
| Predicate Test Results (In Any Order) | | | Final Reference Result |
| --- | --- | --- | --- |
| Result A | Result B | Result C | |
| + | + | (-, Equ, or +) | + |
| - | - | (-, Equ, or +) | - |
| Equ | Equ | (-, Equ, or +) | Equ |
| + | - | Equ | Equ |
All specimens were tested according to the respective package inserts of the FDA-cleared Rubella IgM assays. The three FDA-cleared devices used were the Zeus Scientific Rubella IgM ELISA Test System, the Abbott Labs. AxSYM Rubella IgM Antibody Assay and the DPC Immulite IgM test. Equivocal results that remained equivocal after being retested were considered equivocal for the performance analysis. Any consensus equivocal result discordant with the Elecsys Rubella IgM test result was tallied against the Elecsys in the calculation of performance.
For the vaccine follow up cohort, the Zeus Rubella IgM device was used as the sole comparator.
# b. Matrix comparison:
The effect of analyte detection in the presence of anticoagulants with the Elecsys Rubella IgM was determined on Elecsys 2010 Immunoassay Analyzer by comparing values obtained from samples drawn into Serum-gel Separation-, Li-Heparing-, Citrate-Plasma-, $\mathrm{K}_3$ -EDTA Plasma-, and Plasma Separation tubes. Reference was normal Serum tube without gel. Acceptance criterion for all measurements concerning Serum/Plasma interferences is recovery $\leq 0.5$ S/CO +/- 0.25 S/CO, $>0.5$ S/CO mean recovery $80 - 120\%$ .
The following tables summarize the results for the comparison between serum and 3 plasma matrices.
| Plasma matrix | Number of positive specimens showing recovery to serum within various ranges | | |
| --- | --- | --- | --- |
| | <10% | 10% - 20% | ≥20% |
| Li-heparin | 7 | 1 | 0 |
| K3-EDTA | 3 | 6 | 0 |
| Sodium Citrate | 9 | 0 | 0 |
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| Plasma matrix | Number of negative specimens showing recovery to serum within various ranges | | |
| --- | --- | --- | --- |
| | <0.1 COI | 0.1 - 0.25 COI | >0.25 COI |
| Li-heparin | 24 | 0 | 0 |
| K3-EDTA | 23 | 0 | 0 |
| Sodium Citrate | 23 | 0 | 0 |
# 3. Clinical studies:
a. Clinical Sensitivity: N/A
b. Clinical specificity: N/A
c. Other clinical supportive data (when a. and b. are not applicable):
Percent positive and percent negative agreement with a consensus comparator method was determined as specified under Comparison Studies (see above). Studies were carried out in three independent testing sites (two sites within the US, one in Germany).
# Prospective US clinical study cohort:
501 samples were obtained from a US reference laboratory; representing subjects for whom anti-Rubella testing had been ordered per clinical routine. All samples were frozen sera which had been banked consecutively from the routine collective. 438 were from females (132 of whom were pregnant) and 63 were from males; ages ranged from 18-76 years. Samples were tested on the Elecsys 2010 analyzer and on three FDA-cleared devices, which were used to define a consensus comparator algorithm result using a two-out-of-three approach.
# Clinical routine cohort (non-pregnant)
The following table summarizes the results for the clinical routine cohort (non-pregnant):
| | | Consensus Result Rubella IgM | | | |
| --- | --- | --- | --- | --- | --- |
| Elecsys Rubella IgM | | Positive | Negative | Equivocal | Total |
| | Positive | 0 | 3 | 0 | 3 |
| | Equivocal | 1 | 1 | 0 | 2 |
| | Negative | 0 | 364 | 0 | 364 |
| | Total | 1 | 368 | 0 | 369 |
| Agreement classificationa | Numerator/ Denominator | Percent agreement (%) | 95% confidence interval |
| --- | --- | --- | --- |
| Negative agreement | 364/368 | 98.9 | 97.2 -99.7 |
{11}
Positive agreement 0/1 N/A N/A
e) Discrepant equivocal results were counted against the Elecsys
# Pregnant subjects:
The following tables summarize the overall results for pregnant subjects from the clinical routine cohort:
| | | Consensus Result Rubella IgM | | | |
| --- | --- | --- | --- | --- | --- |
| Elecsys Rubella IgM | | Positive | Negative | Equivocal | Total |
| | Positive | 0 | 0 | 0 | 0 |
| | Equivocal | 0 | 1 | 0 | 1 |
| | Negative | 0 | 131 | 0 | 131 |
| | Total | 0 | 132 | 0 | 132 |
| Agreement classificationd | Numerator/ Denominator | Percent agreement (%) | 95% confidence interval |
| --- | --- | --- | --- |
| Negative agreement | 131/132 | 99.2 | 95.9 -99.98 |
| Positive agreement | 0/0 | N/A | N/A |
d) Discrepant equivocal results were counted against the Elecsys test
# Preselected positive samples cohort:
Due to the extremely low prevalence of IgM positive subjects, 100 additional preselected samples from commercial sources were tested. 100 samples which had tested positive for Rubella IgM were purchased from a US commercial source. All samples were frozen sera. 50 were from females (2 of whom were pregnant) and 50 were from males; ages ranged from 24 - 51 years. Samples were tested in a blinded fashion (together with negative samples).
The following table summarizes the results for all subjects from this preselected cohort:
| | | Consensus Result Rubella IgM | | | |
| --- | --- | --- | --- | --- | --- |
| Elecsys Rubella IgM | | Positive | Negative | Equivocal | Total |
| | Positive | 100* | 0 | 0 | 100 |
| | Equivocal | 0 | 0 | 0 | 0 |
| | Negative | 0 | 0 | 0 | 0 |
| | Total | 100 | 0 | 0 | 100 |
| Agreement classification | Numerator/ Denominator | Percent agreement (%) | 95% confidence interval |
| --- | --- | --- | --- |
| Negative agreement | 0/0 | N/A | N/A |
{12}
* includes two pregnant subjects.
## Vaccination follow up cohort:
Commercially available vaccination follow-up panels comprising 144 samples from 12 subjects (4 male, 8 unknown) were tested to evaluate detection of IgM after vaccination. The first positive bleed of the test was compared to the first positive bleed of the predicate assay, yielding 100 % agreement between the two methods, with 12/12 positive test results.
## Instrument comparison:
Approach to the validation of the different instruments was addressed in a previous FDA decision, see file k072617 for additional details. A total of 313 samples, obtained from blood donors or purchased from commercial sources, were tested on both the Elecsys 2010 and cobas e 411 analyzers and the MODULAR ANALYTICS E170 and cobas e 601 analyzers. Samples had anti-Rubella IgM values ranging from 0.15 - 14.0 COI. The positive agreement was 102/103 or 99.0 % (95 % CI: 95 % - 100 %). The negative agreement was 207/208 or 99.5 % (95 % CI: 97 % - 100 %).
## 4. Clinical cut-off:
Not internationally standard exist for IgM, refer to cutoff section above for additional details.
## 5. Expected values/Reference range:
Reference Range:
| below 0.8 COI | Non reactive |
| --- | --- |
| between = 0.8 and <1.0 COI | Indeterminate |
| equal to or above 1.0 COI | Reactive |
Expected Values: N/A
## N. Proposed Labeling:
The labeling is sufficient and it satisfies the requirements of 21 CFR Part 809.10.
## O. Conclusion:
The submitted information in this premarket notification is complete and supports a substantial equivalence decision.
