(59 days)
Portrait Toxigenic C. difficile Assay, a prescription device under 21 CFR Part 801.109 that is indicated for the detection of toxigenic Clostridium difficile in human fecal samples collected from patients suspected of having Clostridium difficile infection (CDI). The test utilizes automated blocked primer enabled helicase-dependent amplification (bpHDA) to detect toxin gene sequences associated with toxin producing C. difficile. The Portrait Toxigenic C. difficile Assay is intended as an aid in the diagnosis of CDI.
The Portrait Toxigenic C. difficile Assay as run on the Portrait Analyzer is a bench top fully automated in vitro diagnostics system that includes the Portrait Analyzer, control Laptop PC and single-use Portrait Toxigenic C. difficile Test Cartridges and sample preparation apparatus. The Portrait Analyzer is designed to perform automated sample extraction; blocked primer mediated thermophilic helicasedependent amplification (bpHDA); and chip-based detection with integrated data analysis in approximately 85 minutes.
The sample to be tested is inserted into the sample preparation that has been preloaded with buffer and briefly vortexed. The vortexed mixture is then loaded into the assay cartridge. The cartridge is loaded into the Portrait Analyzer which performs extraction (cell lysing), amplification, hybridization and signal formation on the detection chip. The resulting signal(s) are detected and interpreted by the automated Portrait Analyzer.
In addition to the necessary probes and primers to detect the presence of tcdB (toxin B gene) performance of the Portrait Toxigenic C. difficile Assay includes an integrated SPC to insure the adequate processing of the sample during preparation and subsequent extraction and amplification steps.
Here's an analysis of the Portrait Toxigenic C. difficile Assay's acceptance criteria and the study proving it meets them, based on the provided text:
Acceptance Criteria and Device Performance for Portrait Toxigenic C. difficile Assay
1. Table of Acceptance Criteria and Reported Device Performance
The document does not explicitly state pre-defined acceptance criteria in a table format for sensitivity, specificity, PPV, and NPV. However, the reported clinical performance implicitly serves as the criteria the device met for de novo classification. The reproducibility and precision studies also have implicit agreement rate criteria that were "within the expected percent." For this table, I will present the reported clinical performance statistics.
| Metric | Reported Device Performance (%) | Implied Acceptance Criteria (Achieved) |
|---|---|---|
| Sensitivity | 98.0% (92.4-99.6% CI95) | ≥ 92.4% |
| Specificity | 90.9% (87.7-93.3% CI95) | ≥ 87.7% |
| PPV | 71.4% (63.1-78.6% CI95) | ≥ 63.1% |
| NPV | 99.5% (98.0-99.9% CI95) | ≥ 98.0% |
Reproducibility Study Results (Agreement)
| Sample Type | All Sites (%) | Implied Acceptance Criteria (Achieved) |
|---|---|---|
| Moderate Positive | 97.8% | "within the expected percent" |
| Low Positive | 96.7% | "within the expected percent" |
| High Negative | 95.6% | "within the expected percent" |
Precision Study Results (Agreement)
| Sample Type | In-house (%) | Implied Acceptance Criteria (Achieved) |
|---|---|---|
| Moderate Positive | 100% | "within the expected percent" |
| Low Positive | 98.3% | "within the expected percent" |
| High Negative | 93.1% | "within the expected percent" |
2. Sample Size Used for the Test Set and Data Provenance
- Test Set Sample Size (Clinical Evaluation): 540 eligible specimens.
- Data Provenance: The clinical evaluation was a "multi-site clinical evaluation at 4 US institutions." This indicates prospective data collection for the clinical study directly comparing the device to the reference method.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications
The document does not specify the number or qualifications of experts involved in establishing the ground truth for the clinical test set. The ground truth method, "reference culture/cell cytotoxicity (TBC/CCNA) testing," implies laboratory testing rather than expert consensus on interpretation.
For the Reproducibility Study:
- Site 1 (external): Dr. Gerald Denys, PI (Principal Investigator)
- Site 4 (external): Dr. Nate Ledeboer, PI (Principal Investigator)
- The document implies that these PIs oversaw the testing at their respective sites, but it doesn't state they were involved in establishing the ground truth for a test set. Rather, they likely ensured proper execution of the reproducibility protocol.
4. Adjudication Method for the Test Set
The document does not describe any specific adjudication method for establishing the ground truth for the clinical test set. The ground truth was based on "reference culture/cell cytotoxicity (TBC/CCNA) testing."
5. If a Multi Reader Multi Case (MRMC) Comparative Effectiveness Study Was Done
No, a Multi Reader Multi Case (MRMC) comparative effectiveness study was not done. The study compares the device's performance against a reference laboratory method (TBC/CCNA), not against human readers or with AI assistance to human readers.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
Yes, the primary clinical study is a standalone (algorithm only) performance evaluation. The "Portrait toxigenic C. difficile Assay" (the device/algorithm) was directly compared to the "reference culture/cell cytotoxicity (TBC/CCNA) testing." The results (sensitivity, specificity, PPV, NPV) are for the device acting on its own.
7. The Type of Ground Truth Used (expert consensus, pathology, outcomes data, etc.)
The ground truth used for the clinical test set was reference laboratory testing, specifically "reference culture/cell cytotoxicity (TBC/CCNA) testing." This is a gold standard diagnostic method for C. difficile infection.
8. The Sample Size for the Training Set
The document does not provide information regarding a specific training set or its sample size. This is typical for in vitro diagnostic (IVD) devices where the device development often involves internal optimization and verification using various strains and analytical samples (as described in the nonclinical studies), rather than a distinct "training set" in the machine learning sense. The non-clinical studies detail testing with 44 additional toxigenic C. difficile strains and other microorganisms for analytical performance.
9. How the Ground Truth for the Training Set Was Established
As no specific "training set" is described in the provided text in the context of machine learning, there is no information on how its ground truth was established. The analytical performance studies (LoD, cross-reactivity) used known strains and concentrations, where the "ground truth" was inherently defined by the composition of the tested samples.
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EVALUATION OF AUTOMATIC CLASS III DESIGNATION (DE NOVO) FOR PORTRAIT TOXIGENIC C. DIFFICILE ASSAY
REGULATORY INFORMATION
FDA identifies this generic type of device as:
A Clostridium difficile toxin gene amplification assay is a device that consists of reagents for the amplification and detection of target sequences in Clostridium difficile toxin genes in fecal specimens from patients suspected of having Clostridium difficile infection (CDI). The detection of clostridial toxin genes, in conjunction with other laboratory tests, aids in the clinical laboratory diagnosis of CDI caused by Clostridium difficile.
NEW REGULATION NUMBER: 21 CFR 866.3130
CLASSIFICATION: II
PRODUCT CODE: OZN
BACKGROUND
DEVICE NAME: PORTRAIT TOXIGENIC C. DIFFICILE ASSAY
510(K): K113358
DATE OF 510(K) NSE DECISION: FEBRUARY 3, 2012
DATE OF DE NOVO PETITION: MARCH 2, 2012
PETITIONER CONTACT: GREAT BASIN SCIENTIFIC, INC. – MR LARRY REA
PETITIONER'S RECOMMENDED CLASSIFICATION: II
PETITIONER'S RECOMMENDED CONTROLS:
- · Class II Special Controls Guidance Document: Toxin Gene Amplification Assays for the detection of Clostridium difficile.
- · General controls
INDICATIONS FOR USE
Portrait Toxigenic C. difficile Assay, a prescription device under 21 CFR Part 801.109 that is indicated for the detection of toxigenic Clostridium difficile in human fecal samples collected from patients suspected of having Clostridium difficile infection (CDI). The test utilizes automated blocked primer enabled helicase-dependent amplification (bpHDA) to detect toxin gene sequences associated with toxin producing C. difficile. The Portrait Toxigenic C. difficile Assay is intended as an aid in the diagnosis of CDI.
LIMITATIONS
For prescription use only
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PLEASE REFER TO THE LABELING FOR A MORE COMPLETE LIST OF WARNINGS, PRECAUTIONS AND CONTRAINDICATIONS.
DEVICE DESCRIPTION
The Portrait Toxigenic C. difficile Assay as run on the Portrait Analyzer is a bench top fully automated in vitro diagnostics system that includes the Portrait Analyzer, control Laptop PC and single-use Portrait Toxigenic C. difficile Test Cartridges and sample preparation apparatus. The Portrait Analyzer is designed to perform automated sample extraction; blocked primer mediated thermophilic helicasedependent amplification (bpHDA); and chip-based detection with integrated data analysis in approximately 85 minutes.
The sample to be tested is inserted into the sample preparation that has been preloaded with buffer and briefly vortexed. The vortexed mixture is then loaded into the assay cartridge. The cartridge is loaded into the Portrait Analyzer which performs extraction (cell lysing), amplification, hybridization and signal formation on the detection chip. The resulting signal(s) are detected and interpreted by the automated Portrait Analyzer.
In addition to the necessary probes and primers to detect the presence of tcdB (toxin B gene) performance of the Portrait Toxigenic C. difficile Assay includes an integrated SPC to insure the adequate processing of the sample during preparation and subsequent extraction and amplification steps.
SUMMARY OF NONCLINICAL/BENCH STUDIES
- a. The limit of detection (LoD) of the Portrait toxigenic C. difficile Assay for C. difficile was assessed and confirmed by using strains of two different toxinotypes: ATCC strain 43255 (CCUG 19126, VPI 10463), toxinotype 0 A+B+ and ATCC strain 43598 (1470), toxinotype VIII A-B+.
The following Table shows performance of the Portrait Toxigenic C. difficile assay on serial dilutions of two C. difficile strains for initial sensitivity study (CFU/test).
| C. difficile strains | Toxinotype | Tested SerialDilutions(CFU/test) | 'C. difficiledetected |
|---|---|---|---|
| ATCC 43255 (CCUG 19126, VPI 10463) | Type 0 A+B+ | 53.5 | 1/1 |
| ATCC 43255 (CCUG 19126, VPI 10463) | Type 0 A+B+ | 5.35 | 3/4 |
| ATCC 43598 (1470) | Type VIII A-B+ | 177 | 3/3 |
| ATCC 43598 (1470) | Type VIII A-B+ | 88.5 | 3/3 |
| ATCC 43598 (1470) | Type VIII A-B+ | 17.7 | 1/3 |
The following Table shows performance of the Portrait Toxigenic C. difficile Assay on 20 replicates of two C. difficile strains for establishing LoD (CFU/test).
| C. difficile strains | Toxinotype | TestedCFU/test | C. difficile detected |
|---|---|---|---|
| ATCC 43255 (CCUG 19126, VPI10463) | Type 0 A+B+ | 39 | 20/20 |
| ATCC 43598 (1470) | Type VIII A-B+ | 39 | 20/20 |
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b. In addition to the 2 strains used to determine the assay LOD, 44 additional strains of Toxigenic C. difficile were tested in replicates of 3 at concentrations just above the LOD (48 CFU/test), All strains were correctly identified as positive (including four NAP1/B1/027 strains: 2004013, 2004118, 2009292, and ATCC BAA-1805) by the Portrait Toxigenic C. difficile Assay. Toxinotypes and strains tested: Type 0 Strains: 2004111, 2004205, 2004206, 2005022, 2005283, 2006017, 2007070, 2007302, 2008222, 2009078, 2009087, 2009141, Type 0, A+B+: ATCC 9689(90556-M6S), Type A-B+: CCUG 37782 , Type A+B+: ATCC 17857 (870), ATCC43594 (1253), ATCC43594 (W1194), ATCC 43596 (545), ATCC43599 (2022), ATCC 43600 (2149), ATCC 51695 (BDMS 18 AN), ATCC 700792 (14797-2), ATCC BAA-1382 (630), CCUG 9004, CCUG 9018, CCUG 37766, CCUG 37770, CCUG 37774, CCUG 37776, CCUG 37783. CCUG 37784. ATCC BAA-1814. TYPE III: 2004013*, 2004118*, 2005359*, 2009292*, TYPE III A+B+: ATCC BAA-1805, TYPE V: 2005088*, 2005325*, 2007217*, 2007816*, 2007838*,TYPEVIII: 2006376*,TYPE X A-B+: CCUG 20309 (8864)
*C. difficile isolates obtained from the CDC -
c. These studies were done to assess the potential cross-reactivity of the Portrait Toxigenic C. difficile Assay with medically relevant levels of bacteria, viruses and
fungi. Bacteria and fungi were tested at concentrations > 6 x 106 CFU/mL or 1 x 105 TCID50/mL. No cross reactivity was observed. Bacterial strains tested: Aeromonas hydrophila, Bacteroides fragilis, Campylobacter coli, Campylobacter fetus, Campylobacter jejuni, Citrobacter freundii, Clostridium difficile (A-,B-), Clostridium perfringens. Clostridium sordellii. Enterobacter cloacae. Enterococcus faecalis. Enterococcus faecium van A, Escherichia coli, Escherichia coli 0157:H7, Escherichia fergusonii, Escherichia hermannii, Helicobacter pylori. Klebsiella pneumoniae, Lacotococcus lactis, Listeria monocytogenes, Peptostreptococcus anaerobius, Plesiomonas shigelloides, Proteus vulgaris, Pseudomonas aeruginosa, Pseudomonas fluorescens, Salmonella enterica, serovar Typhimurium (group B), Salmonella enterica, serovar Choleraesuis (group C1), Salmonella enterica, serovar Newport (group C2), Salmonella enterica, serovar Typhi (group D), Salmonella enterica, serovar Newington (group E), Serratia liquefaciens, Serratia marcescens, Shigella boydii, Shigella flexneri, Shigella sonnei, Staphylococcus aureus, Staphylococcus aureus Cowan 1, Staphylococcus epidermidis, Vibrio parahaemolyticus, Yersinia entercolitica. Viruses: Adenovirus Type 40, Adenovirus Type 41, Coxsackievirus Type B4, Echovirus Type 11, Rotavirus. Fungi: Candida albicans. Parasites: Cryptosporidium parvum (gDNA), Giardia intestinalis WB clone C6 gDNA. -
d. In addition to the Specificity/Cross reactivity testing, the Portrait toxigenic C. difficile Assay was tested against the same organisms that were used in the Analytical Specificity panel at the specified concentrations against two strains of toxigenic C. difficile spiked into the pooled human stool samples at two times the limit of detection (73 CFU/test). The strains tested were: ATCC 43255 (Toxinotype 0 A+B+) and ATCC 43598 (toxinotype VIII A-B+). All organisms were tested against each strain in triplicate and the Portrait results were positive for all microorganisms tested across both strains.
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Interfering Substances:
The following potentially inhibiting substances were tested without showing Assay Interference:
| Substance | Active Ingredient | Substance | Active Ingredient |
|---|---|---|---|
| Anusol® Plus (TUCKS) | Mineral oil, pramoxine HCl, Zincoxide | Moist Towelettes | water, aloe, glycerin, polysorbate 20,disodium cocoamphodiacetate,tocopheryl acetate,methylchloroisothiazolinone,methylisothiazolinone, quaternium-15, potassium sorbate, disodiumEDTA, Citric acid, fragrance |
| Barium sulfate | Barium sulfate | Miconazole 2% cream (Rite Aid) | Miconazole nitrate 2% |
| Calcium carbonate (TUMS) | Calcium carbonate | Mucin (porcine) | |
| Cimetidine (Tagamet HB 200) | Cimetidine | Naproxen | Naproxen |
| Fecal fats | Stearic acid | (Prilosec OTC) | Omeprazole magnesium |
| Fleet® CB (liquid glycerinlaxative) | Glycerin | Pepto-Bismol® Proctor & Gamble | Bismuth subsalicylate |
| Hydrocortisone Cream(Cortizone-10 max strength) | Hydrocortisone 1% | Preparation H® Wyeth | Glycerin, Phenylephrine HCl,Pramoxine, White petrolatum |
| Imodium® McNeil-PPC | Loperamide HCl | Senna laxative (Rite Aid) | Sennosides |
| Kaopectate® Chattem | Bismuth subsalicylate | Vancomycin Fluka | Vancomycin |
| K-Y Jelly® McNeil-PPC | water, glycerin,hydroxyethylcellulose, chlorhexidinegluconate, gluconolactone,methylparaben, sodium hydroxide | Vaseline Unilever | Petroleum jelly |
| Metranidazole Actavis (0.75%) | Metranidazole | Whole Blood |
Reproducibility:
Reproducibility studies were performed in-house and at two external clinical sites which were provided with masked coded panels of low, moderate and high concentrations of C. difficile. Over the course of five days, two runs were performed with three replicates of each sample per run on each day. A minimum of two operators performed the runs at each site and two different lots of disposable Test Cartridges were used. Results of the Reproducibility studies are summarized in the table below.
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Reproducibility Study Results
| Sample Type | % agreement* | |||
|---|---|---|---|---|
| In-house site | Site 1 (external) | Site 4 (external) | All Sites | |
| Moderate Positive | 30/30 100% | 30/30 100% | 28/30 93.3% | 88/90 97.8% |
| Low Positive | 30/30 100% | 30/30 100% | 27/30 90.0% | 87/90 96.7% |
| High Negative | 27/30 90.0% | 29/30 96.7% | 30/30 100% | 86/90 95.6% |
- For Moderate Positive and Low Positive samples, % agreement = 'C. difficile positive' calls/total
runs. For High Negative samples, % agreement = 'C. difficile ' negative calls/total runs.
- Site 1, Clarion Health Indianapolis, IN (Dr. Gerald Denys, PI)
‡ Site 4, Medical College of Wisconsin, Milwaukee, WI (Dr. Nate Ledeboer , PI)
A precision study was also performed in-house over the course of 12 days. Each day two runs were performed using different operators and two replicates of each sample per run.
| Sample Type | % agreement* | |
|---|---|---|
| Moderate Positive | 58/58 | 100% |
| Low Positive | 57/58 | 98.3% |
| High Negative | 54/58 | 93.1% |
Results of the in-house Precision Study were as follows:
- For Moderate Positive and Low Positive samples, % a greement = 'C. difficile positive' /total runs .
For High Negative samples , % agreement = 'C. difficile 'negative/total runs .
The results for the reproducibility and precision studies of the Portrait Toxigenic C. difficile Assay were within the expected percent across all three sites.
BIOCOMPATIBILITY/MATERIALS
N/A
SHELF LIFE/STERILITY
The Portrait Analyzer has no sterility requirements. The Portrait Toxigenic C. difficile Assay cartridge will be tested to achieve a minimum of 26 weeks stability.
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ANIMAL STUDIES
N/A
ELECTROMAGNETIC COMPATIBILITY AND ELECTRICAL SAFETY
The Portrait Analyzer was tested and complied with the requirements for electromagnetic compatibility.
MAGNETIC RESONANCE (MR) COMPATIBILITY N/A MECHANICAL SAFETY N/A SOFTWARE
| Version: Portrait Analyzer software version 1.5.23.19 | ||
|---|---|---|
| Level of Concern: Moderate | ||
| Yes | No | |
| Software description: | X | |
| Device Hazard Analysis: | X | |
| Software Requirements Specifications: | X | |
| Architecture Design Chart: | X | |
| Design Specifications: | X | |
| Traceability Analysis/Matrix: | X | |
| Development: | X | |
| Verification & Validation Testing: | X | |
| Revision level history: | X | |
| Unresolved anomalies: | X |
The information provided is adequate for each of the items listed above.
Links and relationships between software requirements, specifications, testing and software related hazards are summarized in a Traceability Matrix. In summary, the Analyzer function is controlled by software communicating with hardware drivers and responding to signals from various sensors that monitor fluid, thermal and optical conditions on the assay cartridge. Performance of all individual modules (e.g. Thermal PID Module. Optical Sense Module, etc.) has undergone verification testing at the module level (Intra-Module and Regression Testing), All system related functions have undergone system level verification testing to confirm that all interrelated systems meet all performance specifications.
SUMMARY OF CLINICAL INFORMATION
Clinical performance of the Portrait toxigenic C. difficile Assay was determined in a multi-site clinical evaluation at 4 US institutions by comparison of the Portrait Assay results to reference culture/cell cytotoxicity (TBC/CCNA) testing. A total of 540 eligible specimens were tested with the Portrait toxigenic C. difficile Assay vs.
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TBC/CCNA. Relative to TBC/CCNA, Portrait toxigenic C. difficile Assay demonstrated a sensitivity of 98.0% and a specificity of 90.9% for toxigenic C. difficile when compared to the reference method. The resulting Negative predictive value NPV is 99.5 % and a Positive predictive value of 71.4%.
| Cytotoxic bacterial | |||
|---|---|---|---|
| PortraitC. | Positive | Negative | Total |
| Positive | 100 | 40 | 140 |
| Negative | 2 | 398 | 400 |
| Totals | 102 | 438 | 540 |
| CI95 | ||
|---|---|---|
| Sensitivity | 100/102 98.0% | 92.4-99.6% |
| Specificity | 398/438 90.9% | 87.7-93.3% |
| PPV | 71.4% | 63.1-78.6% |
| NPV | 99.5% | 98.0-99.9% |
CI95: confidence intervals at 95%
PPV: Positive predictive value NPV: Negative predictive value
LABELING
Labeling has been provided which includes instructions for use and an appropriate prescription statement as required by 21 CFR 801.109(b)
RISKS TO HEALTH
The table below identifies the risks to health that may be associated with use of the Clostridium difficile toxin gene amplification assay and the measures recommended to mitigate these risks.
| Identified Risk | Mitigation Method |
|---|---|
| A false positive test result for anindividual may lead to inappropriate useof antibiotics for treatment | Kit includes quality control material andinstructions for use. |
| A false negative test result for anindividual may lead to a potential delayin treatment | Kit includes quality control material andinstructions for use |
| Failure of the test to perform properly | Product labeling provides instructionsfor use and limitations of the assay |
| Failure to properly interpret the testresults | Product labeling describes interpretationof results |
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SPECIAL CONTROLS:
In combination with the general controls of the FD&C Act, the Portrait Toxigenic C. difficile Assay is subject to the following special controls:
-
- The special controls for the Clostridium difficile toxin gene amplification assay are contained in the guidance document: "Class II Special Controls Guidance Document: Toxin Gene Amplification Assays for the Detection of Clostridium difficile."
CONCLUSION
The De Novo petition for the Portrait Toxigenic C. difficile assay is granted and the device is classified under the following:
Product Code: OZN Device Type: Clostridium difficile toxin gene amplification assay Class: II Regulation: 21 CFR 866.3130
§ 866.2660 Microorganism differentiation and identification device.
(a)
Identification. A microorganism differentiation and identification device is a device intended for medical purposes that consists of one or more components, such as differential culture media, biochemical reagents, and paper discs or paper strips impregnated with test reagents, that are usually contained in individual compartments and used to differentiate and identify selected microorganisms. The device aids in the diagnosis of disease.(b)
Classification. Class I (general controls). The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to § 866.9.