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The Xpert® CT/NG test, performed on the GeneXpert® Instrument Systems, is a qualitative in vitro real-time PCR test for the automated detection and differentiation of genomic DNA from Chlamvdia trachomatis (CT) and/or Neisseria gonorrhoeae (NG) to aid in the diagnosis of chlamydial and gonorrheal disease in the urogenital tract and extragenital sites (pharynx and rectum). The assay may be used to test the following specimens from asymptomatic and symptomatic individuals: female and male urine, patient-collected vaginal swabs (collected in a clinical setting), clinician-collected endocervical swabs, and female and male pharyngeal and rectal swabs.

The Xpert CT/NG test is an automated in vitro diagnostic test for qualitative detection and differentiation of DNA from Chlamydia trachomatis (CT) and/or Neisseria gonorrhoeae (NG). The test is performed on the Cepheid GeneXpert Instrument Systems. The Xpert CT/NG test on the GeneXpert Instrument System automates and integrates sample purification, nucleic acid amplification and detection of the target sequences in simple or complex samples using real-time PCR. The system consists of an instrument, personal computer, and preloaded software for running the tests and viewing the results. The system requires the use of single-use disposable cartridges that hold the PCR reagents and host the PCR process. Because the cartridges are self-contained, crosscontamination between samples is minimized.

The Xpert CT/NG test includes reagents for the detection and differentiation of CT and NG. A Sample Processing Control (SPC), a Sample Adequacy Control (SAC), and a Probe Check Control (PCC) are also included. The SPC is present to control for adequate processing of the target bacteria and to monitor the presence of inhibitors in the PCR reaction. The SAC reagents detect the presence of a single copy human gene and monitor whether the specimen contains human cells. The PCC verifies reagent rehydration, PCR tube filling in the cartridge, probe integrity, and dye stability.

The GeneXpert Instrument Systems, comprised of the GeneXpert Dx Systems, the GeneXpert Infinity-48 System. GeneXpert Infinity-48s. and the GeneXpert Infinity-80 System, have 1 to 80 randomly accessible modules, depending upon the instrument, that are each capable of performing separate sample preparation and real-time PCR tests. Each module contains a syringe drive for dispensing fluids (i.e., the syringe drive activates the plunger that works in concert with the rotary valve in the cartridge to move fluids between chambers), an ultrasonic horn for lysing cells or spores, and a proprietary I-CORE® thermocycler for performing real-time PCR and detection.

The ancillary specimen collection kits for use with the Xpert CT/NG test are the Xpert Vaginal/Endocervical Specimen Collection Kit, Xpert Swab Specimen Collection kit and the Xpert Urine Specimen Collection kit.

This looks like a 510(k) summary for the Cepheid Xpert CT/NG test. The document provides information on analytical and clinical performance studies.

Here's a breakdown of the requested information based on the provided text:

1. Table of acceptance criteria and the reported device performance:

The document doesn't explicitly state "acceptance criteria" with numerical targets for clinical performance (sensitivity, specificity) in the same way it defines LoD for analytical sensitivity. However, based on the presentation and context, the reported sensitivities and specificities from the clinical performance study appear to be the performance demonstrated to justify substantial equivalence.

Since the submission is for a 510(k), the implied "acceptance criteria" for clinical performance is that the device's performance is substantially equivalent to a predicate device. The document states "the Xpert CT/NG test performance is equivalent to the predicate" in the conclusions.

Here's a table summarizing the reported clinical performance:

Analytical Sensitivity (LoD) - (Example of explicit acceptance criteria and performance)

• Acceptance Criteria for LoD: The lowest concentration at which 95% of at least 20 replicates are positive.
• Reported Device Performance (LoD - Pharyngeal Swab Matrix):
  • CT ATCC vr885 serovar D: 161 EB/mL
  • CT ATCC vr879 serovar H: 225 EB/mL
  • NG ATCC 19424: 7.1 CFU/mL
  • NG ATCC 49226: 6.4 CFU/mL
• Reported Device Performance (LoD - Rectal Swab Matrix):
  • CT ATCC vr885 serovar D: 88 EB/mL
  • CT ATCC vr879 serovar H: 161 EB/mL
  • NG ATCC 19424: 4.9 CFU/mL
  • NG ATCC 49226: 5.3 CFU/mL

2. Sample size used for the test set and the data provenance:

• Sample Size for Test Set:
  • Pharyngeal Swabs: 2577 specimens (eligible for inclusion in data analyses)
  • Rectal Swabs: 2538 specimens (eligible for inclusion in data analyses)
• Data Provenance:
  • Country of Origin: United States ("multi-site prospective investigational study at 9 US institutions").
  • Retrospective or Prospective: Prospective ("multi-site prospective investigational study").

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

The document does not specify the number of experts or their qualifications for establishing the ground truth. It states that the ground truth was established using an "anatomic site infected status (ASIS) algorithm based on combined results from two NAAT tests, with a tiebreaker NAAT test if applicable." This suggests a reliance on laboratory test results rather than human expert interpretation of raw data.

4. Adjudication method (e.g. 2+1, 3+1, none) for the test set:

The adjudication method used for establishing the ASIS (ground truth) was a form of 2+1 rule:

• The anatomic site was considered infected if both primary reference NAAT test results were positive.
• The anatomic site was considered not infected if both primary reference NAAT test results were negative.
• If there was discordance between the two primary reference tests, an additional (tiebreaker) NAAT was performed. In this case, agreement of 2 out of 3 (two primary reference tests + tiebreaker) determined the ASIS result.

5. If a multi reader multi case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:

No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. This study is an analytical and clinical performance evaluation of an in vitro diagnostic (IVD) nucleic acid amplification test (NAAT), not an AI-assisted diagnostic imaging or interpretation device that would involve human readers.

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:

Yes, a standalone performance study was done. The study directly compares the results of the Xpert CT/NG test (algorithm only) to the established ASIS ground truth for each specimen. There is no human-in-the-loop component mentioned for the interpretation of the Xpert CT/NG results themselves.

7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):

The ground truth used was Anatomic Site Infected Status (ASIS), which was determined by a composite reference method involving multiple nucleic acid amplification tests (NAATs). This is a type of laboratory-based diagnostic ground truth, not pathology, expert consensus on images, or long-term outcomes data.

8. The sample size for the training set:

The document does not provide information on the sample size for a training set. This is typical for traditional in vitro diagnostic (IVD) submissions like this one, as the assay development and validation generally don't utilize "training sets" in the same way machine learning algorithms do. The studies described are for validation of the final device.

9. How the ground truth for the training set was established:

Not applicable, as a distinct training set and its ground truth establishment are not discussed in this document, which focuses on the validation of the Xpert CT/NG assay.

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The Cepheid Xpert® CT/NG Control Panel is intended for use as an external assayed positive and negative quality control to monitor the performance of in vitro laboratory nucleic acid testing procedures for the qualitative detection of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) performed with the Cepheid Xpert® CT/NG assay on the GeneXpert® Instrument System. The controls consist of cultured and inactivated Chlamydia trachomatis and Neisseria gonorrhoeae as the positive control and human cells as the negative control.

The Cepheid Xpert® CT/NG Control Panel is not intended to replace manufacturer controls provided with the device.

The Cepheid Xpert® CT/NG Control Panel is used to monitor the extraction, amplification and detection of the Cepheid Xpert® CT/NG Assay. The Cepheid Xpert® CT/NG Control Panel contains authentic pathogens inactivated by radiological or temperature treatments. Each Cepheid Xpert® CT/NG Control Panel consists of 6 individually packaged positive control swabs and 6 individually wrapped negative control swabs. Each positive control swab contains Chlamydia trachomatis and Neisseria gonorrhoeae as well as preservatives and stabilizers. Each negative control swab contains human cells as well as preservatives and stabilizers. Each swab is individually wrapped with a desiccant in a heat-sealed foil pouch.

The provided text describes the acceptance criteria and performance data for the Cepheid Xpert® CT/NG Control Panel, which is an assayed quality control material for clinical microbiology assays. This is a diagnostic device, not an AI/ML-based device, so many of the requested criteria related to AI/ML studies (such as MRMC studies, training set details, or ground truth establishment by experts for imaging) are not applicable.

Here's an analysis based on the provided document:

1. A table of acceptance criteria and the reported device performance

The acceptance criteria for this device appear to be 100% agreement with expected results for both positive and negative controls. The reported device performance met these criteria.

• C. trachomatis: 92/92 (100%)
• N. gonorrhoeae (NG2): 92/92 (100%)
• N. gonorrhoeae (NG4): 92/92 (100%)
• SPC: 92/92 (100%) |
  | Negative Controls: 100% agreement with expected negative results for all analytes (SAC, SPC) | 100% agreement for all analytes:
• SAC: 97/97 (100%)
• SPC: 97/97 (100%) |
  | Consistency in Ct values across sites and operators (implied by %CV data) | Mean Ct and %CV values were reported across sites, demonstrating consistency. (e.g., Overall Mean Ct for C. trachomatis 31.8 (3.8)). |

2. Sample size used for the test set and the data provenance

• Test Set Sample Size:
  • Positive Controls: 92 replicates were tested across three sites. (31 from Site 1, 31 from Site 2, 30 from Site 3, with some additional runs for re-tests).
  • Negative Controls: 97 replicates were tested across three sites. (33 from Site 1, 34 from Site 2, 30 from Site 3, with some additional runs for re-tests).
• Data Provenance: The data was generated prospectively through a multi-site evaluation. The document does not specify the country of origin of the testing sites, but given it's an FDA submission, it's highly likely to be within the US or under US regulatory guidelines.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts

This is an in vitro diagnostic (IVD) device, specifically a quality control. The "ground truth" is inherent to the control material itself (i.e., the positive control contains the target microbes at a known concentration, and the negative control does not).

Therefore:

• Number of experts: Not applicable in the context of human interpretation for ground truth. The "ground truth" is established by the known composition of the control material (inactivated pathogens for positive, human cells only for negative).
• Qualifications of experts: Not applicable.

4. Adjudication method for the test set

Not applicable for an IVD quality control device. The results are quantitative (Ct values) and qualitative (positive/negative detection) based on the instrument's algorithm, not human interpretation requiring adjudication. Any "ERROR" or "INVALID" results were retested according to the Instructions for Use, which is a standard procedure for IVD testing.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance

Not applicable. This is an IVD quality control device, not an AI/ML imaging or diagnostic aid for human readers.

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done

This device evaluates the performance of the Cepheid Xpert® CT/NG assay and GeneXpert® Instrument System, which is an automated system. The performance data presented demonstrates the "standalone" or "algorithm only" performance of the control panel interacting with the assay/instrument system as intended, without human interpretation as a variable.

7. The type of ground truth used

The ground truth is based on the known composition of the control materials:

• Positive control: Contains cultured and inactivated Chlamydia trachomatis and Neisseria gonorrhoeae.
• Negative control: Contains human cells.

The "expected results" (positive or negative) are determined by these known compositions.

8. The sample size for the training set

Not applicable. This is a manufactured control material, not an AI/ML algorithm that requires a training set. Its development involves formulation and manufacturing processes, followed by validation and verification studies (which are described as the "performance data").

9. How the ground truth for the training set was established

Not applicable, as there is no "training set" in the AI/ML sense for this type of device. The "ground truth" for the control material itself is established during its design and manufacturing by precisely controlling its components.

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The Xpert CT/NG Assay, performed on the GeneXpert Instrument Systems, is a qualitative in vitro real-time PCR test for the automated detection and differentiation of genomic DNA from Chlamydia trachomatis (CT) and/or Neisseria gonorrhoeae (NG) to aid in the diagnosis of chlamydial and gonorrheal urogenital disease. The assay may be used to test the following specimens from asymptomatic individuals: female and male urine, endocervical swab, and patient-collected vaginal swab (collected in a clinical setting).

Ancillary Collection Kits:

Xpert Vaginal/Endocervical Specimen Collection Kit

The Cepheid Xpert Vaginal/Endocervical Specimen Collection Kit is designed to collect, preserve, and transport Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis DNA in endocervical swab specimens (collected by a clinician) and patient-collected vaginal swab specimens (collected in a clinical setting) from symptomatic and asymptomatic women prior to analysis with the Xpert CT/NG Assay and the Xpert TV Assay.

Xpert Urine Specimen Collection Kit

The Cepheid Xpert Urine Specimen Collection Kit is designed to preserve and transport Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis DNA in first-catch female and male urine specimens from symptomatic and asymptomatic individuals prior to analysis with the Xpert CT/NG Assay and the Xpert TV Assay.

The Xpert CT/NG Assay is a rapid, automated in vitro diagnostic test for qualitative detection and differentiation of DNA from Chlamydia trachomatis (CT) and/or Neisseria gonorrhoeae (NG). The assay is performed on the Cepheid GeneXpert Instrument Systems. The Xpert CT/NG Assay on the GeneXpert Instrument System automates and integrates sample purification, nucleic acid amplification and detection of the target sequences in simple or complex samples using real-time PCR. The system consists of an instrument, personal computer, and preloaded software for running the tests and viewing the results. The system requires the use of single-use disposable cartridges that hold the PCR reagents and host the PCR process. Because the cartridges are self-contained, crosscontamination between samples is minimized.

The Xpert CT/NG Assay includes reagents for the detection and differentiation of CT and NG. A Sample Processing Control (SPC), a Sample Adequacy Control (SAC), and a Probe Check Control (PCC) are also included. The SPC is present to control for adequate processing of the target bacteria and to monitor the presence of inhibitors in the PCR reaction. The SAC reagents detect the presence of a single copy human gene and monitor whether the specimen contains human cells. The PCC verifies reagent rehydration, PCR tube filling in the cartridge, probe integrity, and dye stability.

The GeneXpert Instrument Systems, comprised of the GeneXpert Dx Systems, the GeneXpert Infinity-48 System and the GeneXpert Infinity-80 System, have 1 to 80 randomly accessible modules, depending upon the instrument, that are each capable of performing separate sample preparation and real-time PCR tests. Each module contains a syringe drive for dispensing fluids (i.e., the syringe drive activates the plunger that works in concert with the rotary valve in the cartridge to move fluids between chambers), an ultrasonic horn for lysing cells or spores, and a proprietary I-CORE® thermocycler for performing real-time PCR and detection.

The ancillary specimen collection kits for use with the Xpert CT/NG Assay are the Cepheid® Xpert® Vaginal/Endocervical Specimen Collection kit and the Cepheid® Xpert® Urine Specimen Collection kit.

The provided text describes a 510(k) premarket notification for the Xpert CT/NG Assay, a qualitative in vitro real-time PCR test for the detection of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG). This submission is primarily to support the removal of a limitation statement regarding the device's performance in pregnant women, building upon a previously cleared predicate device (K121710).

It's important to note that this document does not describe an AI/ML-based device. It is a molecular diagnostic test. Therefore, many of the requested criteria related to AI/ML device validation (e.g., number of experts for ground truth, MRMC study, training set details) are not applicable to this type of medical device submission.

However, I can extract the relevant information regarding performance criteria and the study conducted to support the change in the intended use.

Here's the breakdown based on the provided document:

Acceptance Criteria and Reported Device Performance

The "acceptance criteria" for this type of submission are typically demonstrating substantial equivalence to a predicate device and showing that the device performs as intended for its specified use. In this specific case, the main goal was to re-evaluate the device's performance in pregnant women to remove a previous limitation.

Since this is a diagnostic test and not an AI/ML device, the performance is typically measured by sensitivity and specificity against a confirmed ground truth, or by demonstrating equivalent performance to a legally marketed predicate device. The document refers back to the original 510(k) (K121710) for most of the detailed analytical and clinical performance characteristics, as the core technology of the device itself has not changed.

Table of Acceptance Criteria and Reported Device Performance (as inferred from the context of a 510(k) for a diagnostic test, particularly the focus within this document):

Note: For a molecular diagnostic test like this, the "acceptance criteria" are usually based on assay validation metrics (e.g., LOD, inclusivity, exclusivity, clinical agreement with a reference method) that would have been established in the predicate device's clearance. This submission focuses on a specific clinical population.

Study Details:

1. Sample sizes used for the test set and the data provenance:

   • Test Set Sample Size: The document states "Reanalysis of the clinical data from 510(k) #K121710 was performed for the specimens collected from women who were pregnant at the time of collection." The exact number of pregnant women's specimens re-analyzed is not provided in this document but would be found in the K121710 submission details.
   • Data Provenance: The data comes from the original clinical study conducted for the predicate device (K121710). The document does not specify the country of origin, nor whether the original study was retrospective or prospective, but clinical studies for FDA clearance are typically prospective.

2. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

   • Not Applicable in the traditional sense for a PCR test. Ground truth for diagnostic tests like this is typically established by:
     • Reference standard methods: Usually a combination of culture, a highly sensitive and specific laboratory-developed test (LDT), or another gold standard for detecting the bacterial DNA/organism.
     • Discrepancy resolution algorithms: In many PCR studies, samples that show discordant results between the investigational device and a comparator method are further tested by a third, highly reliable method (e.g., an in-house PCR with different targets, sequencing).
   • The document does not specify the ground truth method or expert involvement in establishing it, as it refers back to the K121710 submission.

3. Adjudication method for the test set:

   • Not Applicable in the traditional sense of human reader adjudication. For molecular diagnostic tests, ground truth is established by laboratory methods, not by human interpretation of images. Discrepancy resolution for discordant results between methods is a common practice, but it's not "adjudication" by experts in the context of image interpretation. The document doesn't detail this process for the K121710 data reanalysis.

4. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, if so, what was the effect size of how much human readers improve with AI vs without AI assistance:

   • Not Applicable. This is a molecular diagnostic test (PCR), not an AI-assisted imaging device. Human readers are not involved in interpreting results in the way they would be with an AI device for radiology, for example.

5. If a standalone (i.e., algorithm only without human-in-the-loop performance) was done:

   • Partially Applicable / This is a Standalone Device. The Xpert CT/NG Assay is a fully automated, standalone in vitro diagnostic device. It performs sample purification, nucleic acid amplification, and detection without human intervention in the assay process itself. The "performance" is the direct output of the instrument.

6. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):

   • Likely a composite reference standard or culture/validated PCR. For sexually transmitted infections (STIs) detected via nucleic acid amplification tests (NAATs), the ground truth is typically established by using a combination of other highly sensitive and specific laboratory methods (e.g., another validated NAAT, potentially culture for NG, or a rigorous discrepancy resolution algorithm). The document refers to the original K121710 for details.

7. The sample size for the training set:

   • Not Applicable / No separate "training set" for an AI/ML model. For a molecular diagnostic test, there isn't a "training set" in the sense of an AI model. The assay's performance characteristics (e.g., primer design, probe specificity, assay conditions) are optimized during development and then validated using analytical and clinical studies. The data from K121710 was likely used as a "test set" for performance evaluation, not for training a model.

8. How the ground truth for the training set was established:

   • Not Applicable. (As there is no "training set" for an AI/ML model here). The ground truth for the clinical validation would have been established using the accepted reference methods for CT/NG detection, as described in point 6.

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The Xpert® CT/NG Assay, performed on the GeneXpert® Instrument Systems, is a qualitative in vitro real-time PCR test for the automated detection and differentiation of genomic DNA from Chlamydia trachomatis (CT) and/or Neisseria gonorrhoeae (NG) to aid in the diagnosis of chlamydial and gonorrheal urogenital disease. The assay may be used to test the following specimens from asymptomatic and symptomatic individuals: female and male urine, endocervical swab, and patient-collected vaginal swab (collected in a clinical setting).

Ancillary Collection Kits Indications for Use:

The Cepheid® Xpert® CT/NG Vaginal/Endocervical Specimen Collection Kit is designed to collect, preserve and transport patient Chiamydia trachomatis and Neisseria gonorrhoeae DNA in endocervical and vaginal specimens from symptomatic and asymptomatic individuals prior to analysis with the Cepheid Xpert CT/NG Assay.

The Cepheid® Xpert® CT/NG Urine Specimen Collection Kit is designed to preserve and transport Chlamydia trachomatis and Neisseria gonorrhoeae DNA in first-catch male and female urine specimens from symptomatic and asymptomatic individuals prior to analysis with the Cepheid Xpert CT/NG Assay.

The Xpert CT/NG Assay is an automated in vitro diagnostic test for qualitative detection and differentiation of DNA from Chlamydia trachomatis (CT) and/or Neisseria gonorrhoege (NG). The assay is performed on the Cepheid GeneXpert Instrument Systems. The GeneXpert Instrument Systems automate and integrate sample purification, nucleic acid amplification, and detection of the target sequences in simple or complex samples using real-time PCR and RT-PCR assays. The systems consist of an instrument, personal computer, and preloaded software for running the tests on collected samples and viewing the results. The system requires the use of single-use disposable cartridges that hold the PCR reagents and host the PCR process. Because the cartridges are selfcontained, cross-contamination between cartridges during the testing process is minimized.

The Xpert CT/NG Assay includes reagents for the 5' exonuclease real-time PCR detection and differentiation of CT and NG. Reagents for the detection of a Sample Processing Control (SPC), a Sample Adequacy Control (SAC), and a Probe Check Control (PCC) are also included in the cartridge. The SPC is present to control for adequate processing of the target bacteria and to monitor the presence of inhibitors in the PCR reaction. The SAC reagents detect the presence of a single copy human gene and monitor whether the specimen contains human DNA. The PCC verifies reagent rehydration. PCR tube filling in the cartridge, probe integrity, and dye stability. The primers and probes in the Xpert CT/NG Assay detect chromosomal sequences in the bacteria. One target is detected for CT (CT1) and two different targets are detected for NG (NG2 and NG4). Both NG targets need to be positive for the Xpert CT/NG Assay to return a positive NG result.

The GeneXpert Instrument Systems, comprised of the GeneXpert Dx Systems, the GeneXpert Infinity-48 System and the GeneXpert Infinity-80 System, have 1 to 80 randomly accessible modules, depending upon the instrument, that are each capable of performing separate sample preparation and real-time PCR tests. Each module contains a svringe drive for dispensing fluids (i.e., the syringe drive activates the plunger that works in concert with the rotary valve in the cartridge to move fluids between chambers), an ultrasonic horn for lysing cells or spores, and a proprietary I-CORE® thermocycler for performing real-time PCR and detection.

The ancillary specimen collection kits for use with the Xpert CT/NG Assay are the Cepheid® Xpert® CT/NG Vaginal/Endocervical Specimen Collection Kit and the Cepheid® Xpert® CTNG Urine Specimen Collection Kit.

This response describes the acceptance criteria and the study that proves the device meets the acceptance criteria, as extracted from the provided text.

Acceptance Criteria and Device Performance

The acceptance criteria for the Xpert CT/NG Assay are primarily demonstrated through its analytical sensitivity (Limit of Detection - LoD), analytical specificity (cross-reactivity), and clinical performance (sensitivity and specificity compared to a Patient Infected Status algorithm).

Table of Acceptance Criteria and Reported Device Performance (Clinical Performance - Overall "All" Category):

Note: The document does not explicitly state pre-defined numerical "acceptance criteria" thresholds for clinical performance. Instead, it presents the achieved performance metrics, which are then assessed for substantial equivalence to predicate devices.

Study Information

1. Sample sizes used for the test set and data provenance:

• Clinical Study:

  • Female Subjects: A total of 3767 female subjects were included in the overall clinical performance analysis across various specimen types.
    • Patient-Collected Vaginal Swabs (PC-VS) analyzed for CT: 3766 subjects
    • Endocervical Swabs (ES) analyzed for CT: 3757 subjects
    • Female Urine analyzed for CT: 3767 subjects
    • PC-VS analyzed for NG: 3766 subjects
    • ES analyzed for NG: 3757 subjects
    • Female Urine analyzed for NG: 3767 subjects
  • Male Subjects: A total of 3436 male subjects were included in the overall clinical performance analysis.
    • Male Urine analyzed for CT: 3436 subjects
    • Male Urine analyzed for NG: 3436 subjects
  • Data Provenance: The study was a "multi-site prospective investigational study at 36 US and UK institutions". This indicates the data is prospective and collected from multiple countries (United States and United Kingdom).

• Reproducibility Study (Test Set):

  • Panel of 22 specimens (11 in urine matrix, 11 in swab matrix), tested 4 times per day, by 2 operators, for 5 days, across 3 sites.
  • Total replicates per panel member: 22 specimens x (4 runs/day * 5 days * 2 operators * 3 sites) = 120 replicates per panel member.

• Instrument System Precision Study (Test Set):

  • Panel of 20 specimens (10 in urine matrix, 10 in swab matrix), tested on 12 different days by 2 operators, with each operator conducting 4 runs of each panel specimen per day on each of two instrument systems.
  • Total replicates per panel member: 20 specimens x (4 runs/day * 12 days * 2 operators * 2 instrument systems) = Approximately 191-192 total agreement results reported per panel member depending on specific run outcomes (ERROR, INVALID, NO RESULT).

2. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

• The ground truth for the clinical study (Patient Infected Status - PIS) was established using an algorithm based on the results from two currently marketed NAAT tests (predicate devices). The document does not specify the number or qualifications of human experts involved in establishing the PIS, as it relies on a composite reference standard from established molecular diagnostic tests (GEN-PROBE® APTIMA® Combo 2 Assay and Becton Dickenson ProbeTec™ ET Chlamydia trachomatis /Neisseria gonorrhoeae Amplified DNA Assay).

3. Adjudication method for the test set:

• For the clinical study, the PIS algorithm was defined as:
  • Infected (I) for CT or NG: If at least one positive result was reported from each of the two reference NAAT tests.
  • Equivocal (EQ): If both NAAT tests resulted in equivocal results for both sample types (swab and urine). (No study participants fell into this category).
  • Not Infected (NI): Any other combination of results.
  • Specific rules were applied for cases where reference urine was positive and swab negative, or vice versa (e.g., for females, positive on both reference urine and negative on both reference swab would be 'infected' for urine and 'not infected' for swab).
• This approach constitutes a composite reference standard using two predicate devices. It's not a typical human expert adjudication method (e.g., 2+1), but rather an algorithmic adjudication based on existing cleared tests.

4. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, if so, what was the effect size of how much human readers improve with AI vs without AI assistance:

• No MRMC comparative effectiveness study was performed or described. This device is an automated, qualitative in vitro real-time PCR test, meaning it directly detects and differentiates genomic DNA. It does not involve human readers interpreting results, nor does it incorporate AI for diagnostic assistance in the manner typically described in MRMC studies.

5. If a standalone (i.e., algorithm only without human-in-the-loop performance) was done:

• Yes, the clinical performance study evaluated the Xpert CT/NG Assay as a standalone algorithm (device only) against the Patient Infected Status (PIS) algorithm. The device is designed to be fully automated and provides qualitative results (DETECTED, NOT DETECTED), thus it inherently operates without human interpretation of the primary result.

6. The type of ground truth used:

• The ground truth for the clinical performance study was a Patient Infected Status (PIS) algorithm, which served as a composite reference standard. This PIS was derived from the combined results of two predicate (legally marketed) Nucleic Acid Amplification Tests (NAATs): GEN-PROBE® APTIMA® Combo 2 Assay and Becton Dickenson ProbeTec™ ET Chlamydia trachomatis /Neisseria gonorrhoeae Amplified DNA Assay.

7. The sample size for the training set:

• The document describes pre-market non-clinical (analytical) and clinical validation studies. There is no mention of a separate "training set" in the context of machine learning model development. This device is a real-time PCR assay, not a machine learning or AI-based diagnostic that typically undergoes an explicit training phase with a distinct training dataset. The development of such an assay involves analytical optimization and robust validation rather than AI model training.

8. How the ground truth for the training set was established:

• As the device is a real-time PCR assay and not an AI/ML-based system, an explicit "training set" with ground truth in the AI sense is not applicable. The development cycle would involve designing primers and probes, optimizing reaction conditions, and verifying analytical performance against known standards and cultured organisms to establish the assay's ability to detect target DNA. For the non-clinical analytical studies (e.g., LoD, specificity), the ground truth was established by using purified elementary bodies or cells of known organisms at specified concentrations (e.g., ATCC reference strains) or well-characterized human biological samples confirmed negative for the targets.

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