Sofia 2 Campylobacter FIA
Device Facts
| Record ID | K211342 |
|---|---|
| Device Name | Sofia 2 Campylobacter FIA |
| Applicant | Quidel Corporation |
| Product Code | LQP · Microbiology |
| Decision Date | Nov 23, 2021 |
| Decision | SESE |
| Submission Type | Traditional |
| Regulation | 21 CFR 866.3110 |
| Device Class | Class 1 |
| Attributes | Pediatric |
Indications for Use
Sofia 2 Campylobacter FIA employs immunofluorescence for the rapid qualitative detection of a Campylobacter-specific antigen in human fecal specimens. Sofia 2 Campylobacter FIA is designed to detect C. jejuni, C. coli, C. lari and C. upsalients with signs and symptoms of gastroenteritis. The test is intended for use with preserved fecal specimens in transport media and unpreserved fecal specimens. Test results should be considered in conjunction with clinical findings and patient history.
Device Story
Sofia 2 Campylobacter FIA is an immunofluorescence-based lateral-flow assay for rapid qualitative detection of Campylobacter antigens in human fecal specimens. Fecal samples are diluted in specimen solution, filtered, and applied to a test cassette. If specific antigens are present, they bind to fluorescent microparticle-coupled antibodies; these complexes are captured on the test strip. The Sofia 2 instrument scans and interprets the fluorescent signal using method-specific algorithms. Used in clinical settings; operated by healthcare professionals. Provides automated, objective results (Positive, Negative, Invalid) in 15 minutes. Supports 'WALK AWAY' (automated timing) or 'READ NOW' (pre-incubation) modes. Assists clinicians in diagnosing Campylobacter-related gastroenteritis by providing rapid diagnostic information to guide patient management.
Clinical Evidence
Prospective clinical study of 811 fresh specimens (191 neat, 620 in transport media) compared to culture and identification. Sensitivity was 100% (8/8; 95% CI: 67.6%-100%) and specificity was 99.3% (797/803; 95% CI: 98.4%-99.7%). Discordant samples (6/6) were confirmed positive by RT-PCR and sequencing. An archived study of 70 frozen specimens showed 100% correlation with culture and molecular methods.
Technological Characteristics
Lateral-flow test cassette using immunofluorescence technology. Employs monoclonal and polyclonal antibodies specific to Campylobacter antigens. Analyte detection via fluorescent microparticles. Compatible with Sofia 2 instrument for automated signal measurement and interpretation. Storage at room temperature (15°C-30°C).
Indications for Use
Indicated for patients with signs and symptoms of gastroenteritis to detect C. jejuni, C. coli, C. lari, and C. upsaliensis antigens in human fecal specimens (unpreserved or in Cary Blair/C&S media).
Regulatory Classification
Identification
Campylobacter fetus serological reagents are devices that consist of antisera conjugated with a fluorescent dye used to identify Campylobacter fetus from clinical specimens or cultured isolates derived from clinical specimens. The identification aids in the diagnosis of diseases caused by this bacterium and provides epidemiological information on these diseases. Campylobacter fetus is a frequent cause of abortion in sheep and cattle and is sometimes responsible for endocarditis (inflammation of certain membranes of the heart) and enteritis (inflammation of the intestines) in humans.
Predicate Devices
- CAMPYLOBACTER QUIK CHEK (K191456)
Related Devices
- K210976 — Curian Campy · Meridian Bioscience, Inc. · Dec 23, 2021
- K173217 — CAMPYLOBACTER QUIK CHEK · Techlab, Inc. · Jan 22, 2018
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
K211342
B Applicant
Quidel Corporation
C Proprietary and Established Names
Sofia 2 Campylobacter FIA
D Regulatory Information
| Product Code(s) | Classification | Regulation Section | Panel |
| --- | --- | --- | --- |
| LQP | Class I, reserved | 21 CFR 866.3110 - Campylobacter fetus Serological Reagents | MI - Microbiology |
| KHO | Class I, exempt | 21 CFR 862.2560 – Fluorometer for Clinical Use | CH - Clinical Chemistry |
## II Submission/Device Overview:
A Purpose for Submission:
To obtain a substantial equivalence determination for the detection of Campylobacter jejuni, Campylobacter coli, Campylobacter lari, and Campylobacter upsaliensis antigens in human stool.
B Measurand:
Campylobacter jejuni, Campylobacter coli, Campylobacter lari, and Campylobacter upsaliensis antigens.
C Type of Test:
Lateral flow fluorescent immunoassay (FIA)
## III Intended Use/Indications for Use:
Food and Drug Administration
10903 New Hampshire Avenue
Silver Spring, MD 20993-0002
www.fda.gov
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K211342 - Page 2 of 12
A Intended Use(s):
See Indications for Use below.
B Indication(s) for Use:
Sofia 2 Campylobacter FIA employs immunofluorescence for the rapid qualitative detection of a *Campylobacter*-specific antigen in human fecal specimens. Sofia 2 Campylobacter FIA is designed to detect *C. jejuni*, *C. coli*, *C. lari* and *C. upsaliensis* from patients with signs and symptoms of gastroenteritis. The test is intended for use with preserved fecal specimens in transport media and unpreserved fecal specimens. Test results should be considered in conjunction with clinical findings and patient history.
C Special Conditions for Use Statement(s):
- Rx - For Prescription Use Only
- The Sofia 2 Campylobacter FIA was evaluated using only fresh fecal samples and fecal samples stored in Cary Blair media or C&S media. The performance of fecal samples stored in other transport media (e.g., formalin, polyvinyl alcohol) has not been evaluated and therefore, should not be used.
- No data exists on the effects of colonic washes, barium enemas, laxatives, or bowel preparations on the performance of the Sofia 2 Campylobacter FIA. All of these procedures can result in extensive dilution or the presence of additives that may affect test performance.
- The fluorescence signal obtained with this assay is invisible to the unaided eye. The test results can only be obtained with the proper use of Sofia 2
D Special Instrument Requirements:
The Sofia 2 Campylobacter FIA can only be run on the Sofia 2 Instrument.
IV Device/System Characteristics:
A Device Description:
The Sofia 2 Campylobacter FIA is an immunofluorescence-based, lateral flow assay that uses an antibody sandwich design to detect Campylobacter-specific antigens in stool specimens from individuals with signs and symptoms of gastroenteritis.
The patient stool sample is placed in the Specimen Tube, containing Specimen Diluent, to make the antigenic components more accessible to the test antibodies. An aliquot of the diluted sample is dispensed through a filter into the Test Cassette sample well. From the sample well, the sample migrates through a test strip containing various unique chemical environments. If *Campylobacter jejuni*, *Campylobacter coli*, *Campylobacter lari*, or *Campylobacter upsaliensis* specific antigens are present, they will be bound by polyclonal antibodies coupled to fluorescent microparticles that migrate through the test strip. The fluorescent microparticles containing bound antigens will be captured by monoclonal antibodies at a defined location on the test strip where they are detected by Sofia 2. If *Campylobacter jejuni*, *Campylobacter coli*, *Campylobacter lari*, or *Campylobacter upsaliensis* specific antigens are not present, the fluorescent microparticles will not be trapped by the capture antibodies nor detected by Sofia 2.
The Test Cassette is placed inside of Sofia 2 for automatically timed development ("Walk Away" mode), or pre-incubated on the bench top prior to loading into Sofia 2 ("Read Now" mode), where Sofia 2 will scan, measure, and interpret the immunofluorescent signal using method-specific algorithms. Note that a supervisor can place Sofia 2 into Locked Walk Away mode, which only
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allows testing to be performed in Walk Away mode. Once testing is complete, Sofia 2 will display the test results (Positive, Negative, or Invalid) on the screen.
## B Principle of Operation:
Immunofluorescence
## V Substantial Equivalence Information:
## A Predicate Device Name(s):
CAMPYLOBACTER QUIK CHEK
## B Predicate 510(k) Number(s):
K191456
## C Comparison with Predicate(s):
| Similarities | | |
| --- | --- | --- |
| Item | DEVICE
Sofia 2 Campylobacter FIA K211342 | PREDICATE
CAMPYLOBACTER QUIK CHEK K191456 |
| Indications For Use | Sofia 2 Campylobacter FIA employs immunofluorescence for the rapid qualitative detection of a Campylobacter-specific antigen in human fecal specimens. Sofia 2 Campylobacter FIA is designed to detect C. jejuni, C. coli, C. lari, and C. upsaliensis from patients with signs and symptoms of gastroenteritis. The test is intended for use with preserved fecal specimens in transport media and unpreserved fecal specimens. Test results should be considered in conjunction with clinical findings and patient history. | The CAMPYLOBACTER QUIK CHEK test is a rapid membrane enzyme-linked immunosorbent assay for the qualitative detection of a Campylobacter-specific antigen in human fecal specimens. The CAMPYLOBACTER QUIK CHEK test is designed to detect C. jejuni, C. coli, C. lari, and C. upsaliensis from patients with signs and symptoms of gastroenteritis. The test is intended for use with preserved fecal specimens in transport media and unpreserved fecal specimens. Test results should be considered in conjunction with clinical findings and patient history. |
| Classification | I | Same |
| Product Code | LQP | Same |
| Regulation | 21 CFR 866.3110 | Same |
| Measured Analyte | Campylobacter-specific antigen | Same |
| Antibody Format | Monoclonal/Polyclonal | Same |
| Type of Test | Qualitative | Same |
| Sample Matrix | Human fecal specimen | Same |
| Specimen Type | Unpreserved fecal specimens and fecal specimens in Cary-Blair and C&S transport media | Same |
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| Controls | Positive and negative control included in the kit | Same |
| --- | --- | --- |
| Species Detected | C. jejuni, C. coli, C. lari, and C. upsaliensis | Same |
| Differences | | |
| Item | DEVICE
Sofia 2 Campylobacter FIA K211342 | PREDICATE
CAMPYLOBACTER QUIK CHEK K191456 |
| Test Principle | Immunofluorescence device | Immunochromatographic device |
| Format | Lateral-flow test cassette | Membrane Enzyme Linked Immunosorbent Assay (ELISA) |
| Read Result Time | 15 minutes | <30 minutes |
| Result Interpretation Method | Result interpretation automated by Sofia 2 Instrument | Visually Read |
| Kit Storage | Room Temperature (15°C-30°C) | Refrigerated (2°C-8°C) |
VI Standards/Guidance Documents Referenced:
None referenced
VII Performance Characteristics (if/when applicable):
A Analytical Performance:
As noted above, the test can be used in "Walk Away" mode, or "Read Now" mode. The primary difference between these modes is that in "Read Now" mode, the operator is responsible for the incubation time; in the "Walk Away" mode, the instrument will wait to read the strip until the specified development time has passed. In this submission, all analytical studies were conducted in "Read Now" mode. A validation study was conducted to demonstrate that the analytic study results using the "Read Now" mode can be considered representative. See section VII.A.3. "Read Now" vs. "Walk Away" Mode Study for more information and the results of this study.
1. Precision/Reproducibility:
The precision of the Sofia 2 Campylobacter FIA was determined using a 3-member masked fecal sample panel that consisted of a negative, low positive (1-2x higher than C95) and a moderate positive (2-3x higher than C95). Each fecal sample was spiked with C. jejuni (strain CCUG 11284) whole organism to achieve the desired level. The samples were tested once per day over a 20-day period by multiple operators using three reagent lots. A total of 240 tests per panel member (1 run per day x 4 replicates per run x 20-days x 3 lots) were performed. Positive and negative controls were run with each sample panel of masked samples. All replicates for the negative panel member were negative and all replicates for the positive panel members were positive.
The reproducibility of the Sofia 2 Campylobacter FIA was determined using an 8-member masked fecal sample panel. The panel consisted of 2 negatives, 2 high negatives (just below C5), 2 low positives (1-2x higher than C95) and 2 moderate positives (2-3x higher than C95). Each fecal sample was spiked with C. jejuni (strain CCUG 11284) whole organism to achieve the desired level. Testing was performed at three laboratories, one of which was on-site. The samples were tested by 2 operators per day over 5 non-consecutive days with 2 reagent lots for a total of
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90 replicates per panel member (1 run per day x 3 replicates per run x 5-days x 3 sites x 2 lots). In total, 180 measurements were performed for each evaluated Campylobacter concentration (e.g. 2 low positive panel members x 90 replicates per panel member = 180 measurements), for a total of 360 expected positive and 360 expected negative measurements. Positive and negative controls were run with each sample panel of masked specimens. The results were consistent among the three locations with 100% reproducibility for all test panel members.
## 2. Linearity:
Not applicable
## 3. Analytical Specificity/Interference:
### Cross-Reactivity and Microbial Interference
The Sofia 2 Campylobacter FIA was evaluated for cross-reactivity with the bacteria, fungi and viruses listed in Table 1. For cross-reactivity testing, bacteria and fungi were spiked at concentrations >10⁷ CFU/mL and viruses were spiked at concentrations >10⁵ TCID₅₀/mL, unless otherwise noted. For cross-reactivity testing, samples were prepared in the absence of C. jejuni. For microbial interference testing, samples were evaluated in the presence of C. jejuni (strain CCUG 11284), which was spiked at 2-3x LoD with whole organism. Due to safety concerns with culturing Listeria monocytogenes, freeze-dried biomaterial from ATCC was reconstituted in 1 mL of sterile PBS and tested alone (negative sample) or spiked with C. jejuni (strain CCUG 11284) whole organism at 2-3x LoD (positive sample). Four (4) clinically positive Norovirus fecal specimens (determined by RT-PCR) were obtained from a clinical repository (Wyoming Public Health Laboratory). The two specimens that were genogroup I (GGI) were pooled, and the two specimens that were genogroup II (GGII) were pooled. The pooled samples served as negative Campylobacter samples while the pooled specimens spiked with Campylobacter jejuni (strain CCUG 11284) whole organism at 2-3x LoD served as the positive samples.
C. helveticus (strain ATCC 51209) was cross-reactive at 6.3×10⁶ CFU/mL, which is ~3x the LoD of C. lari in unpreserved fecal matrix. Additional C. helveticus concentrations were tested and cross-reactivity was no longer observed at 1.98×10⁵ CFU/mL. No other tested microorganism exhibited cross-reactivity with the Sofia 2 Campylobacter FIA.
Table 1. Microorganisms Evaluated for Cross-Reactivity/Microbial Interference
| Bacteria/Fungi | |
| --- | --- |
| Acinetobacter baumannii | Escherichia hermannii |
| Aeromonas hydrophila | Helicobacter pylori |
| Bacillus cereus | Klebsiella pneumoniae |
| Bacillus subtilis | Lactobacillus acidophilus |
| Bacteroides fragilis | Lactococcus lactis |
| Campylobacter concisus | Listeria monocytogenes |
| Campylobacter fetus | Peptostreptococcus anaerobius |
| Campylobacter helveticus | Plesiomonas shigelloides |
| Campylobacter hyointestinalis | Porphyromonas asaccharolytica |
| Candida albicans | Prevotella melaninogenica |
| Citrobacter freundii | Proteus vulgaris |
| Clostridium bifermentans | Pseudomonas fluorescens |
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| Bacteria/Fungi | |
| --- | --- |
| Clostridiodes difficile | Salmonella enterica typhimurium |
| Clostridium perfringens | Serratia marcescens |
| Edwardsiella tarda | Shigella dysenteriae |
| Enterobacter cloacae | Shigella flexneri |
| Enterococcus faecalis | Shigella sonnei |
| Escherichia coli | Staphylococcus aureus |
| Escherichia coli EIEC | Staphylococcus aureus subsp. aureus Rosenbach [formerly Cowan’s] |
| Escherichia coli EPEC | Streptococcus agalactiae |
| Escherichia coli ETEC | Staphylococcus epidermidis |
| Escherichia coli O157:H7 (non-toxigenic) | Vibrio parahaemolyticus |
| Escherichia coli O157:H7 (toxigenic) | Yersinia enterolitica |
| Escherichia fergusonii | |
| Viruses | |
| Adenovirus Type 1 | Enterovirus 69 |
| Adenovirus Type 2 | Enterovirus 70 |
| Adenovirus Type 3 | Enterovirus 71 |
| Adenovirus Type 5 | Human coronavirus |
| Human mastadenovirus F [formerly Adenovirus Type 40]¹ | Echovirus 9 |
| Adenovirus Type 41 | Echovirus 11 |
| Coxsackie virus B2 | Echovirus 18 (ATCC VR-1783) |
| Coxsackie virus B3 | Echovirus 18 (NCPV 0801131v)³ |
| Coxsackie virus B4 | Human parechovirus 1 [formerly Echovirus 22] |
| Coxsackie virus B5 | Echovirus 33⁴ |
| Human Rotavirus² | Norovirus GI |
| Enterovirus 68 | Norovirus GII |
¹Tested at 1.6 x 10⁴ TCID₅₀/mL
²Tested at 5.0 x 10⁶.⁷⁵ TCID₅₀/mL
³Tested at 5.6 x 10³ TCID₅₀/mL
⁴Tested at 1.0 x 10⁴ TCID₅₀/mL
## Interfering Substances Study
The Sofia 2 Campylobacter FIA was evaluated for interference with the substances and concentrations listed in Table 2. Samples were tested in triplicate in both the presence and absence of C. jejuni (strain CCUG 11284) whole organism. Positive samples were spiked with C. jejuni at 2-3x LoD. At the concentrations tested, none of the substances listed in Table 2 were shown to interfere with the performance of the Sofia 2 Campylobacter FIA.
Table 2. Interfering Substances
| Substance | Concentration | Substance | Concentration |
| --- | --- | --- | --- |
| Barium sulfate | 5% w/v | Naproxen Sodium | 0.05% w/v |
| Benzalkonium Chloride | 1% w/v | Nonoxynol-9 | 1% w/v |
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| Ciprofloxacin | 0.25% w/v | Nystatin | 1% w/v |
| --- | --- | --- | --- |
| Ethanol | 1% w/v | Palmitic Acid/Fecal Fat | 40% w/v |
| Hog gastric mucin | 3.5% w/v | Pepto-Bismol® | 5% v/v |
| Human blood | 40% v/v | Phenylephrine | 1% w/v |
| Hydrocortisone | 1% w/v | MiraLax® | 10% w/v |
| Imodium® | 5% v/v | Prilosec OTC® | 5 μg/mL |
| Kaopectate® | 5% v/v | Sennosides | 1% w/v |
| Leukocytes | 0.05% w/v | Simethicone | 10% w/v |
| Maalox® Advanced | 5% v/v | Stearic Acid/Fecal Fat | 40% w/v |
| Mesalazine | 10% w/v | TUMS® | 50 μg/mL |
| Metronidazole | 0.25% w/v | Human Urine | 5% v/v |
| Mineral Oil | 10% w/v | Vancomycin | 0.25% w/v |
| Mylanta® | 4.2 mg/mL | | |
## Prozone Study
The purpose of this study was to demonstrate that a high concentration of Campylobacter (antigen) does not interfere with a positive reaction in the Sofia 2 Campylobacter FIA. High positive samples were prepared by spiking a negative fecal pool with 5.0x10⁷ CFU/mL whole organisms of C. jejuni (strain CCUG 11284), 2.4x10⁸ CFU/mL whole organisms of C. coli (strain CCUG 11283), 1.6x10⁸ CFU/mL whole organisms of C. lari (strain 2015/1582), and 1.3x10⁸ whole organisms of C. upsaliensis (strain 2018/0319H). A total of 5 different dilutions for each Campylobacter species were prepared and tested. Testing was performed in triplicate according to the Package Insert instructions. The results demonstrated that there was no overall hook affect, and that elevated levels of whole organism did not affect the detection of Campylobacter.
## "Read Now" vs. "Walk Away" Mode Study
To demonstrate that performance of the Sofia 2 Campylobacter FIA is not influenced by operating the device in "Read Now" mode under the conditions used for analytical studies, a comparison study was conducted with positive samples prepared by spiking a negative fecal pool with C. jejuni (strain CCUG 11284) at 3x LoD. Negative samples were also included. Each sample was tested in replicates of twenty using five Sofia 2 analyzers. Testing was completed once with Sofia 2 analyzers in "Read Now" mode and once with Sofia 2 analyzers in "Walk Away" mode.
There was 100% agreement between the expected and observed results for all positive and negative samples. These results demonstrate that there is no notable difference in performance between "Read Now" and "Walk Away" modes in the analytical testing setting. These study results are acceptable and support performing analytical testing solely in "Read Now" mode.
4. Assay Reportable Range: Not applicable
5. Traceability, Stability, Expected Values (Controls, Calibrators, or Methods):
## Specimen Stability
The effect of specimen storage on antigen stability was evaluated for both unpreserved stool samples and samples in Cary Blair and C&S transport media. For the analysis, a total of 22 fecal specimens were tested with the Sofia 2 Campylobacter FIA. The fecal specimens consisted of 10 C. jejuni low positive fecal samples (1-2x LoD), 5 C. jejuni moderate positive fecal samples (2-
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3x LoD), 5 C. jejuni high positive fecal samples (4-5x LoD) and 2 negative samples. C. jejuni strain CCUG 11284 was used to generate the positive samples.
Unpreserved and preserved stool samples were stored at room temperature (15-30°C) and refrigerated (2-8°C) and tested at 24 hour intervals for 120 hours. Positive and negative controls were also tested. The following transport media were used for the study: ThermoFisher Protocol Cary Blair media and ThermoFisher Protocol C&S. Positive samples remained positive and negative samples remained negative throughout the study. Storage in transport media did not affect the stability of the samples. Based on these results, the recommended storage time for unpreserved and preserved (Cary Blair and C&S) stool samples is up to 96 hours at room temperature (15-30°C) and refrigerated (2-8°C).
Unpreserved stool was also stored frozen (i.e., -10°C) and tested at 0, 5, 10, and 14 days. Positive samples at all concentrations remained positive and negative samples remained negative throughout the study. Based on these results, the recommended storage time for unpreserved stool samples is up to 13 days frozen at ≤-10°C.
## Freeze/Thaw Stability
Freeze/Thaw stability for unpreserved specimens was evaluated for five freeze/thaw cycles over a 7-day period. C. jejuni, C. coli, C. lari, and C. upsaliensis were each tested by spiking whole organisms into unpreserved stool at the following concentrations: high negative (~0.5x LoD), low positive (1-2x LoD), and high positive (3-5x LoD). For C. jejuni, 4 high negatives, 15 low positives, and 4 high positive samples were prepared and tested. For each of the remaining Campylobacter species, 2 high negatives, 5 low positives, and 2 high positives were tested. All samples were tested in duplicate. For this study, samples were stored at -10°C.
At baseline, 5 of 15 C. jejuni low positive samples yielded one negative replicate and one positive replicate. Repeat testing was performed on 4 of these samples in duplicate, and 3 samples yielded two positive results, while one sample yielded 2 negative results. All subsequent timepoints were positive for the C. jejuni low positive sample, thus the baseline false negative results were considered acceptable. No other sample converted from positive-to-negative or negative-to-positive after any of the freeze/thaw cycles. The data support a claim for four freeze/thaw cycles and demonstrates that freezing neither enhances nor impairs the performance of the Sofia 2 Campylobacter FIA.
## 6. Detection Limit:
### Limit of Detection Study
The limit of detection (LoD) of the Sofia 2 Campylobacter FIA was determined by spiking whole organism culture preparations of Campylobacter jejuni (strain CCUG 11284), Campylobacter coli (strain CCUG 11283), Campylobacter lari (strain 2015/1582), and Campylobacter upsaliensis (strain 2018/0319H) into negative fecal matrix and Cary Blair and C&S transport media. The LoD is defined as the concentration of Campylobacter (in CFU/mL) that yields a positive result 95% of the time and negative result 5% of the time. The LoD was determined for two Sofia 2 Campylobacter FIA cassette lots. For each lot, multiple dilutions of C. jejuni, C. coli, C. lari, and C. upsaliensis were tested in replicates of 20. The LoD values in Table 3 represent the cassette lot yielding the highest (i.e., least sensitive) LoD. The LoDs were similar between lots.
Table 3. LoD Values for the Sofia 2 Campylobacter FIA
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| Species | Fecal Matrix | | Cary Blair | | C&S | |
| --- | --- | --- | --- | --- | --- | --- |
| | CFU/mL | CFU/test | CFU/mL | CFU/test | CFU/mL | CFU/test |
| C. jejuni | 9.82x104 | 2.95x102 | 1.57x105 | 4.38x102 | 1.50x105 | 4.19x102 |
| C. coli | 1.15x106 | 3.45x103 | 1.59x106 | 4.44x103 | 9.02x105 | 2.52x103 |
| C. lari | 2.00x106 | 6.00x103 | 1.75x106 | 4.88x103 | 2.25x106 | 6.28x103 |
| C. upsaliensis | 5.21x106 | 1.56x104 | 5.21x106 | 1.45x104 | 2.71x106 | 7.56x103 |
## Inclusivity Study
The reactivity (inclusivity) study was conducted using C. jejuni and C. coli strains from the Culture Collection University of Gothenburg (CCUG). The reactivity of C. upsaliensis and C. lari were evaluated using clinical isolates obtained from patients with symptoms of gastroenteritis that were isolated at the Centre National de Reference des Campylobacters et Helicobacters – Universite de Bordeaux between 2015 and 2018. The strains are listed in Table 4. For reactivity testing, each strain was spiked into negative fecal matrix at 2-3x the LoD of the corresponding reference strain used to confirm the LoD, and then tested with the Sofia 2 Campylobacter FIA. All results were positive.
Table 4. Strains Evaluated for Reactivity with the Sofia 2 Campylobacter FIA
| C. jejuni | C. coli | C. upsaliensis | C. lari |
| --- | --- | --- | --- |
| CCUG 6951 | CCUG 10956 | 2016/1950 | 2015/2189 |
| CCUG 12081 | CCUG 17755 | 2016/2826 | 2015/1657 |
| CCUG 29411 | CCUG 36994 | 2017/0349 | 2015/2983 |
| CCUG 38106 | CCUG 53138 | 2018/1669 | 2016/1130H |
| CCUG 24567¹ | | | |
¹ CCUG 24567 is a C. jejuni subspecies doylei isolate.
Additional inclusivity testing was performed for select strains of C. coli, C. lari, and C. upsaliensis to verify the lowest concentration of each strain that is reactive in the Sofia 2 Campylobacter FIA. Four-fold serial dilutions for each of the targeted strains were prepared from stock culture slurries using negative fecal matrix and tested in replicates of three in the assay. The qualitative results were used to determine the lowest detectable level in the series, where 3/3 results were positive (Table 5). The results demonstrated that these strains produced positive results in the assay at concentrations below the limit of detection established with the corresponding reference strains. Note: the purpose of this study was not to set a true limit of detection, but the results are used to demonstrate inclusivity of these strains at the specified concentrations detected (bolded in Table 5).
Table 5. Results of Additional Inclusivity Testing
| Species/Strain Tested | Dilution | Concentration (cfu/mL) | N | Pos | Neg | % Pos. |
| --- | --- | --- | --- | --- | --- | --- |
| Campylobacter coli
CCUG 53138
Stock 2.2 x 10⁷ CFU/mL | Stock slurry | 2.2 x 10⁷ | 3 | 3 | 0 | 100 |
| | 1:4 | 5.5 x 10⁶ | 3 | 3 | 0 | 100 |
| | 1:16 | 1.375 x 10⁶ | 3 | 3 | 0 | 100 |
| | 1:64 | 3.438 x 10⁵ | 3 | 3 | 0 | 100 |
| | 1:256 | 8.594x 10⁴ | 3 | 3 | 0 | 100 |
| | 1:1024 | 2.148 x 10⁴ | 3 | 0 | 3 | 0 |
| | 1:4096 | 5.371 x 10³ | 3 | 0 | 3 | 0 |
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| Species/Strain Tested | Dilution | Concentration (cfu/mL) | N | Pos | Neg | % Pos. |
| --- | --- | --- | --- | --- | --- | --- |
| Campylobacter lari
2015/2189
Stock 1.55 x 10^{7} CFU/mL | Stock slurry | 1.55 x 10^{7} | 3 | 3 | 0 | 100 |
| | 1:4 | 3.875 x 10^{6} | 3 | 3 | 0 | 100 |
| | 1:16 | 9.688 x 10^{5} | 3 | 3 | 0 | 100 |
| | 1:64 | 2.422 x 10^{5} | 3 | 3 | 0 | 100 |
| | 1:256 | 6.055 x 10^{4} | 3 | 3 | 0 | 100 |
| | 1:1024 | 1.514 x 10^{4} | 3 | 0 | 3 | 0 |
| | 1:4096 | 3.784 x 10^{3} | 3 | 0 | 3 | 0 |
| Campylobacter lari
2016/1130H
Stock 1.4 x 10^{7} CFU/mL | Stock slurry | 1.4 x 10^{7} | 3 | 3 | 0 | 100 |
| | 1:4 | 3.5 x 10^{6} | 3 | 3 | 0 | 100 |
| | 1:16 | 8.75 x 10^{5} | 3 | 3 | 0 | 100 |
| | 1:64 | 2.188 x 10^{5} | 3 | 3 | 0 | 100 |
| | 1:256 | 5.469 x 10^{4} | 3 | 0 | 3 | 0 |
| | 1:1024 | 1.367 x 10^{4} | 3 | 0 | 3 | 0 |
| | 1:4096 | 3.418 x 10^{3} | 3 | 0 | 3 | 0 |
| Campylobacter upsaliensis
2016/1950
Stock 8.4 x 10^{7} CFU/mL | Stock slurry | 8.4 x 10^{7} | 3 | 3 | 0 | 100 |
| | 1:4 | 2.1 x 10^{7} | 3 | 3 | 0 | 100 |
| | 1:16 | 5.25 x 10^{6} | 3 | 3 | 0 | 100 |
| | 1:64 | 1.313 x 10^{6} | 3 | 3 | 0 | 100 |
| | 1:256 | 3.281 x 10^{5} | 3 | 2 | 1 | 67 |
| | 1:1024 | 8.203 x 10^{4} | 3 | 0 | 3 | 0 |
| | 1:4096 | 2.051 x 10^{4} | 3 | 0 | 3 | 0 |
7. Assay Cut-Off:
To determine the preliminary cut-off the Sofia 2 Campylobacter FIA read on the Sofia 2 Analyzer, a panel of clinical positive, clinical negative, and contrived positive (near LoD) stool samples were evaluated. After the initial cut-offs were established, the values were validated as part of the clinical trial as well as the other analytical studies.
B Comparison Studies:
1. Method Comparison with Predicate Device: Not applicable
2. Matrix Comparison: Not applicable
C Clinical Studies:
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1. Clinical Sensitivity:
Prospective Study
The performance of the Sofia 2 Campylobacter FIA was assessed with specimens prospectively collected from patients with signs and symptoms of gastroenteritis. Specimens were collected from two independent clinical sites. The sensitivity and specificity of the Sofia 2 Campylobacter FIA was calculated by comparing directly to culture results performed at both sites. Prospective testing consisted of 811 stool specimens tested in clinical microbiology laboratories at the Medical College of Wisconsin and TriCore Reference Laboratories. Both “Read Now” and “Walk Away” modes were used for specimen testing.
The ages of patients ranged from 2 years to 93 years with 3% of the specimens coming from patients that were ≤ 18 years. Of the 811 patients tested, 61.9% were female and 38.1% were male. No difference in test performance was observed based on patient age or gender.
A summary of the clinical performance of the Sofia 2 Campylobacter FIA for both sites, combined is shown in Table 6.
The results of the study show that the Sofia 2 Campylobacter FIA exhibited a sensitivity of 100% and a specificity of 99.3% compared to culture. The lower bound of the two-sided 95% confidence interval for the sensitivity point estimate was slightly lower than expectations for this type of assay. However, the sensitivity results were deemed acceptable without the need to conduct additional clinical specimen testing for the following reasons: (1) Challenges with performing prospective clinical studies during the COVID-19 pandemic and, (2) The prospective study was supplemented with archived positive specimens (see section VII.C.Archived Study, below).
All samples with discrepant results were tested at a third site using an in-house species-specific RT-PCR method and bidirectional sequencing. Of the 6 false positive results, all were confirmed to be positive using these additional tests.
Table 6. Clinical Performance of the Sofia 2 Campylobacter FIA
| | Culture | | | |
| --- | --- | --- | --- | --- |
| | | Positive | Negative | Total |
| Sofia 2 Campylobacter FIA | Positive | 8 | 6* | 14 |
| | Negative | 0 | 797 | 797 |
| | Total | 8 | 803 | 811 |
| | | | | |
| Sensitivity | | 100% (8/8), 95% CI: (67.6% - 100%) | | |
| Specificity | | 99.3% (797/803), 95% CI: (98.4% - 99.7%) | | |
*All specimens that were culture negative and Sofia 2 Campylobacter FIA positive were confirmed to be Campylobacter positive by a species-specific RT-PCR method and bidirectional sequencing.
Archived Study
Additional testing was performed at the third clinical site on 70 retrospectively collected specimens with culture results. The study included 35 positive and 35 negative specimens by Campylobacter spp. culture. The patient ages ranged from 2 years to 87 years. All positive specimens were further characterized as Campylobacter spp. positive by a validated in-house RT-PCR (targeting species-specific genes) and by bidirectional sequencing (targeting sequences of the 16S rRNA gene of Campylobacter spp. and species-specific genes for identification). These
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specimens were then tested by the Sofia 2 Campylobacter FIA. With this information, FDA was able to assess if "weak positives" were included in the archived study and determine performance of the Sofia 2 Campylobacter FIA with such specimens. All 35 specimens tested positive for Campylobacter spp. by all methods, yielding 100% correlation with all test methods.
## Rare Isolate Contrived Study
The performance of the Sofia 2 Campylobacter FIA was further evaluated by testing a panel consisting of five C. coli, five C. upsaliensis, and five C. lari isolates. The C. coli strains were obtained from the Culture Collection University of Gothenburg. The C. upsaliensis and C. lari strains are clinical isolates obtained from the Centre National de Reference des Campylobacters et Helicobacters – Universite de Bordeaux. All samples were prepared by spiking negative, pooled fecal matrix with whole organism at 2x the LoD of the reference strain, which was used to confirm the LoD. Both unpreserved stool and preserved stool (Cary Blair and C&S transport media) were evaluated during the study. Due to availability of a limited number of isolates, each isolate and matrix type were tested in triplicate, twice a day over a period of three days for a total of 18 data points. Ninety datapoints per Campylobacter species and matrix were performed (18 data points/isolate x 5 isolates per species = 90 data points). The results of this study demonstrated 100% positive percent agreement (PPA) with expected results for all C. coli and C. upsaliensis isolates, regardless of matrix. For C. lari, 100% PPA with expected results was obtained for all isolates in unpreserved stool and C&S transport media. For C. lari in Cary Blair media, 98.9% PPA was obtained due to a single negative result. Upon retesting the sample that yielded a negative result, a positive result was obtained. These results are acceptable.
2. Clinical Specificity: See section VII.C.1.Prospective Study above.
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: Not applicable
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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