← Product Code [NXO](/submissions/IM/subpart-f%E2%80%94immunological-test-systems/NXO) · K191718

# Buhlmann fCAL turbo and CALEX Cap (K191718)

_Buhlmann Laboratories AG · NXO · Sep 24, 2019 · Immunology · SESE_

**Canonical URL:** https://fda.innolitics.com/submissions/IM/subpart-f%E2%80%94immunological-test-systems/NXO/K191718

## Device Facts

- **Applicant:** Buhlmann Laboratories AG
- **Product Code:** [NXO](/submissions/IM/subpart-f%E2%80%94immunological-test-systems/NXO.md)
- **Decision Date:** Sep 24, 2019
- **Decision:** SESE
- **Submission Type:** Traditional
- **Regulation:** 21 CFR 866.5180
- **Device Class:** Class 2
- **Review Panel:** Immunology
- **Attributes:** Pediatric

## Indications for Use

The BÜHLMANN fCAL turbo is an in vitro diagnostic assay intended for the quantitative measurement of fecal calprotectin, a neutrophilic protein that is a marker of intestinal mucosal inflammation, in human stool. The BÜHLMANN fCAL turbo aids in the diagnosis of inflammatory bowel disease (IBD), specifically Crohn's disease (CD) and ulcerative colitis (UC) and aids in the differentiation of IBD from irritable bowel syndrome (IBS) in conjunction with other laboratory and clinical findings. The BÜHLMANN CALEX Cap is a single use tube intended for the preparation of human stool samples to be used with the BÜHLMANN fCAL turbo.

## Device Story

Device consists of CALEX Cap, a single-use tube for stool sample collection and extraction, used with previously cleared BÜHLMANN fCAL turbo assay. CALEX Cap replaces manual weighing for sample preparation; provides 1:500 dilution. Assay uses particle-enhanced turbidimetric immunoassay (PETIA) on clinical chemistry analyzers (Roche cobas c501/c502). Stool extracts incubated with polystyrene nanoparticles coated with calprotectin-specific avian polyclonal antibodies; calprotectin mediates immunoparticle agglutination. Turbidity measured via light absorbance at 546 nm; proportional to calprotectin concentration. Results quantified via interpolation on calibration curve. Used in clinical laboratories; results interpreted by clinicians to support IBD diagnosis and differentiation from IBS.

## Clinical Evidence

Clinical performance evaluated via method comparison (n=248) against BÜHLMANN fCAL ELISA and extraction method comparison (n=241) between CALEX Cap and manual weighing. Passing-Bablok regression showed high correlation (r=0.972 vs ELISA; r=0.921 vs manual). Clinical sensitivity/specificity for IBD vs IBS/non-IBD established: sensitivity 91.1% (borderline positive) and 80.0% (borderline negative); specificity 76.2% (borderline positive) and 85.1% (borderline negative). Precision studies (repeatability, reproducibility) performed across multiple sites/days/lots with %CVs generally <15%.

## Technological Characteristics

PETIA assay; polystyrene nanoparticles coated with avian polyclonal antibodies. Analyzed on clinical chemistry analyzers (Roche cobas c501/c502) at 546 nm. CALEX Cap is a single-use plastic extraction tube containing buffer. Measuring range: 30–2,000 μg/g (direct) or 30–10,000 μg/g (automated dilution). Traceable to internal standard (recombinant MRP8/14 dimer).

## Regulatory Identification

A fecal calprotectin immunological test system is an in vitro diagnostic device that consists of reagents used to quantitatively measure, by immunochemical techniques, fecal calprotectin in human stool specimens. The device is intended for in vitro diagnostic use as an aid in the diagnosis of inflammatory bowel diseases (IBD), specifically Crohn's disease and ulcerative colitis, and as an aid in differentiation of IBD from irritable bowel syndrome.

## Special Controls

The device is classified as Class II under regulation 21 CFR 866.5180 with special controls. The special control guidance document, "Class II Special Controls Guidance Document: Fecal Calprotectin Immunological Test Systems" will be available shortly.

*Classification.* Class II (special controls). The special control for these devices is FDA's guidance document entitled “Class II Special Controls Guidance Document: Fecal Calprotectin Immunological Test Systems.” For the availability of this guidance document, see § 866.1(e).

## Predicate Devices

- BÜHLMANN fCAL turbo ([K190784](/device/K190784.md))

## Submission Summary (Full Text)

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Food and Drug Administration
10903 New Hampshire Avenue
Silver Spring, MD 20993-0002
www.fda.gov

# 510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY

## I Background Information:

A 510(k) Number
K191718

B Applicant
BÜHLMANN Laboratories AG

C Proprietary and Established Names
BÜHLMANN fCAL turbo and CALEX Cap

D Regulatory Information
|  Product Code(s) | Classification | Regulation Section | Panel  |
| --- | --- | --- | --- |
|  NXO | Class II | 21 CFR 866.5180 - Fecal Calprotectin Immunological Test System | IM - Immunology  |

## II Submission/Device Overview:

A Purpose for Submission:
BÜHLMANN requests clearance for CALEX Cap for use with the previously cleared BÜHLMANN fCAL turbo assay (K190784). The current submission provides study data obtained from extraction reproducibility, method comparison, and extract and CALEX Cap stability to support the performance of CALEX Cap.

B Measurand:
Fecal calprotectin

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C Type of Test:

Quantitative, Particle-enhanced turbidimetric immunoassay (PETIA)

III Intended Use/Indications for Use:

A Intended Use(s):

See Indications for Use below.

B Indication(s) for Use:

The BÜHLMANN fCAL turbo is an in vitro diagnostic assay intended for the quantitative measurement of fecal calprotectin, a neutrophilic protein that is a marker of intestinal mucosal inflammation, in human stool. The BÜHLMANN fCAL turbo aids in the diagnosis of inflammatory bowel disease (IBD), specifically Crohn's disease (CD) and ulcerative colitis (UC) and aids in the differentiation of IBD from irritable bowel syndrome (IBS) in conjunction with other laboratory and clinical findings.

The BÜHLMANN CALEX Cap is a single use tube intended for the preparation of human stool samples to be used with the BÜHLMANN fCAL turbo.

C Special Conditions for Use Statement(s):

Rx - For Prescription Use Only

D Special Instrument Requirements:

Roche cobas c501/c502

IV Device/System Characteristics:

A Device Description:

The BÜHLMANN fCAL turbo (herein referred to as fCAL turbo) is a particle-enhanced turbidimetric immunoassay (PETIA) intended for the automated quantitative determination of fecal calprotectin in human stool extracts using marketed clinical chemistry analyzers. The fCAL turbo was cleared by the FDA under K190784; with the exception of labeling updates, there have been no changes to the assay.

The CALEX Cap is a single use tube filled with Extraction Buffer. The device is used to sample stool specimens and extract calprotectin. The CALEX Cap is an alternative to manual extraction methods and leads to a final sample dilution of 1:500. Stool specimen extracts

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prepared using the CALEX Cap can be directly measured using the fCAL turbo.

## B Principle of Operation:

The fCAL turbo test is a particle enhanced turbidimetric immunoassay (PETIA) which allows for automated quantification of calprotectin in fecal extracts on clinical chemistry analyzers. Fecal samples are extracted with extraction buffer using the manual weighing or CALEX Cap sampling and extraction method and applied at a final dilution of 1:500. The extracts are incubated with reaction buffer and mixed with polystyrene nanoparticles coated with calprotectin-specific antibodies (immunoparticles).

Calprotectin available in the sample mediates immunoparticle agglutination. Sample turbidity, measured by light absorbance, increases with calprotectin-immunoparticle complex formation and is proportional to calprotectin concentration. The detected light absorbance allows quantification of calprotectin concentration via interpolation on an established calibration curve.

## V Substantial Equivalence Information:

### A Predicate Device Name(s):

BÜHLMANN fCAL turbo

### B Predicate 510(k) Number(s):

K190784

### C Comparison with Predicate(s):

|  Device & Predicate Device(s): | K191718 | K190784  |
| --- | --- | --- |
|  Device Trade Name | BÜHLMANN fCAL turbo and CALEX Cap | BÜHLMANN fCAL turbo  |
|  General Device Characteristic Similarities |  |   |
|  Intended Use/Indications For Use | The BÜHLMANN fCAL turbo is an in vitro diagnostic assay intended for the quantitative measurement of fecal calprotectin, a neutrophilic protein that is a marker of intestinal mucosal inflammation, in human stool. The BÜHLMANN fCAL turbo aids in the diagnosis of inflammatory bowel disease | The BÜHLMANN fCAL turbo is an in vitro diagnostic assay intended for the quantitative measurement of fecal calprotectin, a neutrophilic protein that is a marker of intestinal mucosal inflammation, in human stool. The BÜHLMANN fCAL turbo aids in the diagnosis of  |

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|   | (IBD), specifically Crohn's disease (CD) and ulcerative colitis (UC) and aids in the differentiation of IBD from irritable bowel syndrome (IBS) in conjunction with other laboratory and clinical findings.
The BÜHLMANN CALEX Cap is a single use tube intended for the preparation of human stool samples to be used with the BÜHLMANN fCAL turbo. | inflammatory bowel disease (IBD), specifically Crohn's disease (CD) and ulcerative colitis (UC) and aids in the differentiation of IBD from irritable bowel syndrome (IBS) in conjunction with other laboratory and clinical findings.  |
| --- | --- | --- |
|  Analyte | Human fecal calprotectin (MRP8/14) | Same  |
|  Assay format | Quantitative | Same  |
|  Specimen type | Human stool | Same  |
|  Clinical Decision Thresholds | Normal: < 80 μg/g
Gray-zone: 80–160 μg/g
Elevated: > 160 μg/g | Same  |
|  Solid Phase | Polystyrene nanoparticles (beads) | Same  |
|  Detection Method | Automated clinical chemistry analyzer read at 546 nm | Same  |
|  Antibody | Avian polyclonal antibodies against human calprotectin coated on polystyrene beads | Same  |
|  Measuring Range | Direct measuring range: 30–2,000 μg/g
Measuring range with automatic dilution: 30–10,000 μg/g | Same  |
|  Calibrator Level | 6 levels:
Target values: 0, 50, 200, 500, 1000, 2000 μg/g | Same  |
|  Calibrator Source | Native human calprotectin from human granulocyte extract | Same  |
|  Calibrator Configuration | Available as a separate BÜHLMANN fCAL turbo Calibrator Kit | Same  |

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|  Control Level | 2 (low and high) | Same  |
| --- | --- | --- |
|  Control Source | Native human calprotectin from human granulocyte extract | Same  |
|  Control Configuration | Available as a separate BÜHLMANN fCAL turbo Control Kit | Same  |
|  General Device Characteristic Differences |  |   |
|  Extraction Method | Manual Weighing (1:50 dilution in Extraction Buffer) | Same  |
|   |  CALEX Cap (1:500 dilution in Extraction Buffer) | Not applicable  |
|  Extraction Storage | Extract obtained by manual weighing:
2–8°C for 11 days
-20°C for 2 months | Same  |
|   |  CALEX Cap extracts:
2–8°C for 3.5 days | Not applicable  |

VI Standards/Guidance Documents Referenced:

- Class II Special Controls Guidance Document: Fecal Calprotectin Immunological Test Systems - Guidance for Industry and FDA Staff, JULY 2006
- CLSI EP05-A3 Evaluation of Precision of Quantitative Measurement Procedures; Approved Guideline – Third Edition
- CLSI EP6-A Evaluation of The Linearity of Quantitative Measurement Procedures: A Statistical Approach; Approved Guideline
- CLSI EP07-A2 Interference Testing in Clinical Chemistry; Approved Guideline – Second Edition
- CLSI EP10-A2 Preliminary Evaluation of Quantitative Clinical Laboratory Measurement Procedures Interference Testing in Clinical Chemistry; Approved Guideline – Second Edition
- CLSI EP17-A2 Evaluation of Detection Capability for Clinical Laboratory Measurement Procedures; Approved Guideline – Second Edition
- CLSI EP25-A Evaluation of Stability of In Vitro Diagnostic Reagents; Approved Guideline

VII Performance Characteristics (if/when applicable):

A Analytical Performance:

1. Precision/Reproducibility:
To evaluate extraction reproducibility, stool samples in three different categories of stool consistency with one liquid (Sample 7), seven semi-solid (Sample 1, 3, 4, 6, 8, 11, and 12),

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and four solid samples (Sample 2, 5, 9, and 10) were each extracted using three lots of CALEX Cap by two operators and tested with two extractions with three replicates per extraction over two days, for a total of 72 BÜHLMANN fCAL turbo test results obtained per sample. For each sample, the mean BÜHLMANN fCAL turbo test result was calculated and the within-extraction, between-extraction, total standard deviations (SD) and associated coefficients of variation (%CV) were calculated.

|  Sample | Mean (μg/g) | Within-run |   | Between-extraction |   | Between-day |   | Between-Lot |   | Between-operator |   | Total  |   |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   |   |  SD | %CV | SD | %CV | SD | %CV | SD | %CV | SD | %CV | SD | %CV  |
|  1 | 42.7 | 3.2 | 7.5 | 4.6 | 10.8 | 0.0 | 0.0 | 2.7 | 6.3 | 0.0 | 0.0 | 6.2 | 14.5  |
|  2 | 71.5 | 3.9 | 5.4 | 6.9 | 9.6 | 9.4 | 13.1 | 0.0 | 0.0 | 0.0 | 0.0 | 12.2 | 17.1  |
|  3 | 111.3 | 3.3 | 2.9 | 14.2 | 12.7 | 0.0 | 0.0 | 6.8 | 6.1 | 7.8 | 7.0 | 17.9 | 16.1  |
|  4 | 119.8 | 2.9 | 2.4 | 7.2 | 6.0 | 5.8 | 4.8 | 0.0 | 0.0 | 0.0 | 0.0 | 9.7 | 8.1  |
|  5 | 213.0 | 3.2 | 1.5 | 27.9 | 13.1 | 0.0 | 0.0 | 0.0 | 0.0 | 9.0 | 4.2 | 29.5 | 13.8  |
|  6 | 297.2 | 3.7 | 1.2 | 24.5 | 8.2 | 13.5 | 4.6 | 18.0 | 6.1 | 12.3 | 4.1 | 35.6 | 12.0  |
|  7 | 561.2 | 5.5 | 1.0 | 18.6 | 3.3 | 66.1 | 11.8 | 0.0 | 0.0 | 0.0 | 0.0 | 68.9 | 12.3  |
|  8 | 610.0 | 4.7 | 0.8 | 74.3 | 12.2 | 28.2 | 4.6 | 0.0 | 0.0 | 0.0 | 0.0 | 79.6 | 13.1  |
|  9 | 940.4 | 12.2 | 1.3 | 152.7 | 16.2 | 34.8 | 3.7 | 0.0 | 0.0 | 97.5 | 10.4 | 184.9 | 19.7  |
|  10 | 1558.4 | 7.8 | 0.5 | 152.0 | 9.8 | 39.9 | 2.6 | 98.6 | 6.3 | 146.2 | 9.4 | 236.4 | 15.2  |
|  11 | 2041.6 | 27.2 | 1.3 | 150.3 | 7.4 | 133.8 | 6.6 | 88.9 | 4.4 | 10.5 | 0.5 | 221.9 | 10.9  |
|  12 | 3440.0 | 48.7 | 1.4 | 177.7 | 5.2 | 321.5 | 9.3 | 0.0 | 0.0 | 0.0 | 0.0 | 370.5 | 10.8  |

Other precision studies for BÜHLMANN fCAL turbo were evaluated in K190784.

2. Linearity: Evaluated in K190784
3. Analytical Specificity/Interference: Evaluated in K190784
4. Assay Reportable Range: Evaluated in K190784
5. Traceability, Stability, Expected Values (Controls, Calibrators, or Methods): Traceability: No international reference material or reference measurement procedures are available for calprotectin. Therefore, metrological traceability to international (SI) units cannot be established. The BÜHLMANN fCAL turbo is traceable to an internal standard generated by mixing a recombinant calprotectin antigen (MRP8/14 dimer) with the BÜHLMANN B-CAL-EX extraction buffer. Final

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value assignment was performed with the BÜHLMANN fCAL turbo using multiple reagent lots.

Stability: CALEX Cap Real-time stability: CALEX Cap was stored at 2–8°C. The test samples were stored at –20°C and all necessary reagents were stored at 2–8°C. The test samples and CALEX Cap were equilibrated to room temperature for at least one hour before extracting and testing stool samples. CALEX Cap was stable for up to 29 months. The real time stability claim of CALEX Cap is 24 months at 2–8°C.

CALEX Cap Transport Stability: CALEX Cap was stored at 28 or 37°C for 1, 2, 3, and 4 weeks. The test samples and CALEX Cap were equilibrated to room temperature for at least one hour before extracting and testing stool samples. The transport stability claim of CALEX Cap is 4 weeks up to 37°C.

CALEX Cap Extract Real-time stability: The sample extracts were stored at 2–8°C after the stool samples were extracted using CALEX Cap. The CALEX Cap extracts were stable for 3.5 days (84 hours) at 2–8°C.

Expected Values: Evaluated in K190784

6. Detection Limit:
Evaluated in K19078

7. Assay Cut-Off:
|  Calprotectin Concentration | Interpretation | Follow-Up  |
| --- | --- | --- |
|  < 80 μg/g | Normal | None  |
|  80 μg/g ≤ x ≤ 160 μg/g | Gray-zone/Borderline | Retest within 4–6 weeks  |
|  > 160 μg/g | Elevated | Repeat as needed  |

B Comparison Studies:

1. Method Comparison between BÜHLMANN fCAL ELISA and BÜHLMANN fCAL turbo (K190784):
Evaluated in K190784

2. Extraction Method Comparison for BÜHLMANN fCAL turbo:
A total of 241 samples were obtained for the extraction method comparison study; test results with the samples prepared using the manual weighing and the CALEX Cap extraction method within the measuring range for BÜHLMANN fCAL turbo (n = 202) were included in the regression analysis. The study subject population consisted of: 93 samples from patients with IBD (72 adults and 21 pediatric); 34 samples from patients with IBS (25 adults and 9 pediatric); 37 samples from patients with other GI conditions (34 adults and 3 pediatric); and 38 samples from normal healthy adults. The linear regression analysis obtained from Passing-Bablok regression analysis comparing BÜHLMANN fCAL turbo test results using

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the manual weighing method to corresponding BÜHLMANN fCAL turbo test results using the CALEX Cap method is shown below:

|  N | Range (μg/g) | Slope (95% CI) | Intercept (95% CI) | R | % Bias at 80 μg/g (95% CI) | % Bias at 160 μg/g (95% CI)  |
| --- | --- | --- | --- | --- | --- | --- |
|  202 | 31.6–9,869.8 | 1.149 (1.100–1.201) | -8.3 (-17.1– -2.0) | 0.921 | 4.6 (-4.3–9.1) | 9.7 (4.2–13.8)  |

All 241 samples were used in a qualitative assessment of the assay. The study subject population consisted of 101 samples from patients with IBD (78 adults and 23 pediatric), 42 samples from patients with IBS (32 adult and 10 pediatric), 44 samples from patients with other GI conditions (41 adult and 3 pediatric), and 54 samples from normal healthy adults. Agreement was calculated between test results with BÜHLMANN fCAL turbo using the manual weighing method compared to corresponding test results using the CALEX Cap method. The comparison analysis was performed using cut-offs of both assays and the number of study subjects at each level. The results are shown in the table below:

|   | Subject number in BÜHLMANN fCAL turbo with CALEX Cap (μg/g)  |   |   |   |   |
| --- | --- | --- | --- | --- | --- |
|   |   |  < 80 | 80–160 | > 160 | Total  |
|  Subject number in BÜHLMANN fCAL turbo with manual weighing (μg/g) | < 80 | 71 | 8 | 0 | 79  |
|   |  80–160 | 3 | 30 | 4 | 37  |
|   |  > 160 | 0 | 3 | 122 | 125  |
|  Total |   | 74 | 41 | 126 | 241  |

Estimates of percent agreement, positive percent agreement (PPA) and negative percent agreement (NPA), between BÜHLMANN fCAL turbo assay results using manual weighing and BÜHLMANN fCAL turbo assay results using CALEX Cap are shown below:

|  Metric | Estimate | 95% C.I.  |
| --- | --- | --- |
|  PPA at 80μg/g cutoff | 159/162 = 98.1% | [94.7%, 99.6%]  |
|  NPA at 80μg/g cutoff | 71/79 = 89.9% | [81.0%, 95.5%]  |
|  PPA at 160μg/g cutoff | 122/125 = 97.6% | [93.1%, 99.5%]  |
|  NPA at 160μg/g cutoff | 112/116 = 96.6% | [91.4%, 99.1%]  |

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3. Matrix Comparison: Not applicable

C Clinical Studies:

1. Clinical Sensitivity: Evaluated in K190784
2. Clinical Specificity: Evaluated in K190784
3. Other Clinical Supportive Data (When 1. and 2. Are Not Applicable): Not applicable

D Clinical Cut-Off:

Not applicable

E Expected Values/Reference Range:

Evaluated in K190784

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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**Source:** [https://fda.innolitics.com/submissions/IM/subpart-f%E2%80%94immunological-test-systems/NXO/K191718](https://fda.innolitics.com/submissions/IM/subpart-f%E2%80%94immunological-test-systems/NXO/K191718)

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