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The ASI Automated RPR (rapid plasma reagin) Test for Syphilis, for use on the ASI Evolution Automated Analyzer, is a qualitative and semiquantitative flocculation test for the detection of nontreponemal antibodies in human serum and plasma to aid in the diagnosis of syphilis. All reactive RPR test samples should be further tested with a treponemal test to determine serological evidence of syphilis infection. The test is intended to be used for in vitro diagnostic testing.

The ASI Evolution is an integrated digital particle analyzer designed to objectively interpret certain slide agglutination tests manufactured by Arlington Scientific. Inc. (ASI). The ASI Evolution fully automates the sample and reagent handling steps of the test procedure. Qualitative and semiquantitative tests are performed by laboratory professionals who use the ASI Evolution to provide standardized test interpretation using criteria that define reactive and nonreactive agglutination reactions.
The ASI Evolution employs a camera that uses light reflectance to create a highly sensitive and high-resolution image of the agglutination immunoassay. This image is then analyzed by the proprietary software algorithm to interpret the agglutination pattern.

The ASI Evolution further provides tools that enable the creation, storage, retrieval and transmittal of the test results.

The ASI Automated RPR Test for Syphilis reagents include the following:

CARBON ANTIGEN - 0.003% cardiolipin, 0.020-0.022% lecithin, 0.09% cholesterol, charcoal (activated) as visual enhancer, phosphate buffer, 0.1% sodium azide as preservative and stabilizers.

CONTROLS (REACTIVE, WEAK REACTIVE, NONREACTIVE) - Human serum or defibrinated plasma (liquid), with 0.1% sodium azide as preservative.

Reagents have two-year expiration dating from date of manufacture. The specific expiration date is located on the label on the vial.

Here's a breakdown of the acceptance criteria and the study proving the device meets them, based on the provided FDA 510(k) summary:

This submission is for a new algorithm for an existing device, the ASI Evolution Automated Syphilis Analyzer, used with the ASI Automated RPR Test for Syphilis. The study aims to demonstrate substantial equivalence of the new algorithm to the original algorithm. Therefore, the acceptance criteria and study design are geared towards showing comparable performance rather than de novo validation against a clinical gold standard.

Acceptance Criteria and Reported Device Performance

The acceptance criteria are implicitly defined by the goal of demonstrating substantial equivalence to the original algorithm. This means the new algorithm's performance (positive agreement and negative agreement) should be comparable to or better than the original algorithm's. While explicit numerical thresholds for acceptance are not stated for agreement, the 95% Confidence Intervals are provided, which typically are evaluated against a pre-defined acceptance range (e.g., lower bound of 90% for positive agreement). The reproducibility section demonstrates 100% agreement, which is a strong indicator of meeting a high standard for reproducibility.

Table of Acceptance Criteria (Implicit) and Reported Device Performance (Calculated from provided data)

Details of the Study Proving Device Meets Acceptance Criteria

1. Sample Sizes Used for the Test Set and Data Provenance:

• Retrospective Study Comparing Algorithms:
  • Serum Samples: 872 individual retrospective samples.
  • Plasma Samples: 890 individual retrospective samples.
  • Pregnant Women Testing: 280 samples (30 reactive, 250 nonreactive).
  • Total Samples for Algorithm Comparison: 872 (serum) + 890 (plasma) + 280 (pregnant women) = 2042 samples.
• Reproducibility Study:
  • 7 samples (2 nonreactive, 2 reactive 1:2, 1 reactive 1:4, 1 reactive 1:8, 1 reactive 1:16).
  • Each sample tested in duplicate within the panel, for 5 non-consecutive days, producing 60 data points per sample (60/60 reported). Total 7 samples x 60 data points = 420 data points.
• End-point Titer Testing:
  • 9 samples (2 nonreactive, 7 reactive with varying titers).
  • Each sample tested in 8 replicates on 10 different days, resulting in 80 data points for each sample. Total 9 samples x 80 data points = 720 data points.
• Data Provenance: Retrospective samples, with identifiers removed, collected from different Departments of Public Health Labs and Blood Banks. No specific country of origin is mentioned, but "U.S. Food & Drug Administration" implies U.S. data.

2. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications of Those Experts:

• For Algorithm Equivalence Study: The "ground truth" for the algorithm comparison study was the results interpreted by the original ASI Evolution algorithm (K173376 and K182391). This device was already cleared by the FDA, implying its outputs were considered reliable. No human experts were explicitly stated to establish ground truth for this direct comparison between two algorithms. However, for discordant results:
  • The 6 discordant serum results (new algorithm nonreactive, original algorithm reactive) were investigated and tested with a treponemal test and found to be reactive. This implies confirmation by an independent, more specific test, which is a common form of "ground truth" for syphilis diagnosis.
  • The 6 discordant plasma results (1 new reactive/original nonreactive, 5 new nonreactive/original reactive) were investigated. The new reactive/original nonreactive sample was tested with a treponemal test and found to be nonreactive. The 5 new nonreactive/original reactive samples were attributed to bubbles or artifacts in the test well. This also points to investigation and confirmation using a more definitive test or root cause analysis, serving as a form of expert adjudication or outcome-based truth.
• For Reproducibility and End-point Titer Testing: The "Expected Result" for these tests was established either by the manual interpretation method prior to testing (for end-point titer samples) or by the known characteristics of the control samples used. This implies laboratory or subject matter expert consensus or established reference values.

3. Adjudication Method for the Test Set:

• For the algorithm comparison (serum and plasma), discordant results between the new and original algorithms were investigated using a treponemal test (for biological confirmation) or attributed to technical issues (e.g., bubbles/artifacts). This serves as an adjudication method based on a more definitive test or root cause analysis.
• For the pregnant women testing, the comparison was made against the "ASI RPR Card Test for Syphilis on the ASiManager-AT Result," which acts as the reference.
• No explicit "2+1" or "3+1" human expert adjudication method was described as the primary ground truth establishment for the algorithm comparison, as the goal was algorithm-to-algorithm equivalence rather than algorithm-to-human.

4. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done:

• No, an MRMC comparative effectiveness study was not performed as the primary validation for this submission. The study focused on demonstrating substantial equivalence between two automated algorithms (new vs. original ASI Evolution algorithm), not on comparing human readers with and without AI assistance.
• Effect size of human readers improving with AI vs. without AI assistance: Not applicable to this study design.

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

• Yes, the core of the submission is a standalone performance study comparing the new algorithm's interpretation capabilities against the existing, cleared original algorithm on the same instrument. The "Performance Data" section explicitly states, "A comparison of the digital interpretation of the results from the ASI Evolution using the original interpretation algorithm... to establish substantial equivalence to the interpretation made by the ASI Evolution using the new interpretation algorithm was conducted."

6. The Type of Ground Truth Used:

• Algorithm vs. Algorithm (Predicate Device as Reference): The primary "ground truth" for the main algorithm comparison study was the output of the predicate device's algorithm (original ASI Evolution algorithm).
• Confirmatory Treponemal Test: For discrepant results in the algorithm comparison studies, a treponemal test was used as a more definitive clinical ground truth to resolve ambiguities.
• Manual Interpretation Methods / Known Reactivity: For reproducibility and end-point titer testing, the "expected result" was based on prior manual interpretation methods or known characteristics of control samples.
• No pathology or direct outcomes data was cited as the primary ground truth for the device clearance.

7. The Sample Size for the Training Set:

• Not specified in the provided document. The document describes a study comparing the new algorithm's performance against the old one (test set). It does not provide details about if or how the new algorithm itself was "trained" using specific data. Given the context of medical device clearance, it's presumed that the algorithm development (training, if any) would have occurred prior to this validation study.

8. How the Ground Truth for the Training Set was Established:

• Not specified in the provided document. As the training set details are not provided, neither is the method for establishing its ground truth.

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The ASI Automated RPR (rapid plasma reagin) Test for Syphilis, for use on the ASI Evolution Automated Syphilis Analyzer, is a qualitative and semi-quantitative nontreponemal flocculation test for the detection of reagin antibodies in human serum and plasma as a screening test for serological evidence of syphilis. All reactive RPR test samples should be further tested with a treponemal test. The ASI Automated RPR Test for Syphilis is for professional use only. The test is intended to be used for in vitro diagnostic testing and blood donor screening.

The ASI Evolution is intended to be used as a fully automated analyzer to objectively interpret the results of the ASI Automated RPR Test for Syphilis. The ASI Evolution is designed to provide standardized test interpretation and to provide for storage, retrieval, and transmittal of the test results. It is intended to be acquired, possessed and used only by health care professionals. The ASI Evolution analyzer, in conjunction with the ASI Automated RPR Test for Syphilis is intended to be used for in vitro diagnostic testing and blood donor screening.

The Automated RPR Test for Syphilis performed on the ASI Evolution is an automated nontreponemal flocculation test for the detection of reqain antibodies in human serum and plasma.

The ASI Evolution is an integrated digital particle analyzer designed to objectively interpret certain slide agglutination tests manufactured by Arlington Scientific, Inc. (ASI). The ASI Evolution fully automates the sample and reagent handling steps of the test procedure. Qualitative and semiquantitative tests are performed by laboratory professionals who use the ASI Evolution to provide standardized test interpretation using criteria that define reactive and nonreactive agglutination reactions.

The ASI Evolution employs a camera that uses light reflectance to create a highly sensitive and high-resolution image of the agglutination immunoassay. This image is then analyzed by the proprietary software algorithm to interpret the agglutination pattern.

The ASI Evolution further provides tools that enable the creation, storage, retrieval and transmittal of the test results.

The ASI Automated RPR Test for Syphilis reagents include the following:

CARBON ANTIGEN - 0.003% cardiolipin, 0.020-0.022% lecithin, 0.09% cholesterol, charcoal (activated) as visual enhancer, phosphate buffer, 0.1% sodium azide as preservative and stabilizers.

CONTROLS (REACTIVE, WEAK REACTIVE, NONREACTIVE) - Human serum or defibrinated plasma (liguid), with 0.1% sodium azide as preservative.

Reagents have two-year expiration dating from date of manufacture. The specific expiration date is located on the label on the vial.

The provided text describes the acceptance criteria and the study that proves the device meets those criteria for the ASI Automated RPR Test for Syphilis on the ASI Evolution, specifically focusing on the semi-quantitative claim for endpoint titer determination.

Here's a breakdown of the requested information:

1. Table of Acceptance Criteria and Reported Device Performance

2. Sample Sizes Used for the Test Set and Data Provenance

• Test Set Description: A randomized and blinded panel of 10 human serum samples with known reagin antibody endpoint titers.
• Sample Size: Each of the 10 samples was tested a minimum of 80 times, for a total of 800 tests (10 samples * 80 tests/sample).
  • 2 of the 10 samples were non-reactive (total 160 non-reactive tests).
  • 8 of the 10 samples were reactive (total 640 reactive tests).
• Data Provenance: The tests were performed in-house on at least five different days by one operator using a single ASI Evolution instrument. The origin of the human serum samples themselves (e.g., country of origin) is not explicitly stated, but they are described as having "known reagin antibody endpoint titers." The study can be considered prospective as it involved testing pre-selected samples with the device to determine its performance against established ground truth.

3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications

• The ground truth for the 10 human serum samples (known reagin antibody endpoint titers) was "determined by the ASI RPR Card Test for Syphilis on the ASiManager-AT."
• The document does not explicitly state the number or qualifications of experts used to establish the ground truth via the ASI RPR Card Test on the ASiManager-AT. It implies that this was an established method of determining titers, rather than an expert consensus process for this specific study.

4. Adjudication Method for the Test Set

• None specified. The study setup describes the device's output being compared directly against the "known reagin antibody endpoint titers" established by the ASiManager-AT, implying a direct comparison rather than an adjudication process between human readers or the device.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

• No. The provided text describes an analytical study evaluating the semi-quantitative performance (endpoint titer validation) of the automated system. It does not include an MRMC study comparing human reader performance with and without AI assistance for this specific indication.
• The document mentions "Clinical performance of the ASI Automated RPR Test for Syphilis on the ASI Evolution was evaluated under K173376," but focuses on overall qualitative detection rather than human reader AI assistance.

6. Standalone (Algorithm Only Without Human-in-the-Loop Performance) Study

• Yes. The described study is a standalone performance evaluation of the ASI Evolution device itself, as it automates the interpretation of the RPR test. The device's proprietary software algorithm analyzes the image and interprets the agglutination pattern to report results (Reactive, Nonreactive, endpoint titers).

7. Type of Ground Truth Used

• The ground truth used was "known reagin antibody endpoint titers," which were "determined by the ASI RPR Card Test for Syphilis on the ASiManager-AT." This can be classified as a reference standard method (another established diagnostic test) rather than direct pathology or outcomes data from patients.

8. Sample Size for the Training Set

• The sample size for the training set is not specified in the provided text. The document describes pre-market validation for the analytical performance and refers to previous clinical performance evaluations (K173376) for qualitative detection. It does not provide details on the data used to train the proprietary software algorithm itself.

9. How the Ground Truth for the Training Set Was Established

• As the training set size is not specified, how its ground truth was established is also not detailed in this document. It is implicitly understood that for an automated system, the training data would also require established ground truth to enable the algorithm to learn to interpret agglutination patterns, but the specifics are not provided here.

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The ASI Automated RPR (rapid plasma reagin) Test for Syphilis, for use on the ASI Evolution Automated Syphilis Analyzer, is a qualitative nontreponemal flocculation test for the detection of reagin antibodies in human serum and plasma as a screening test for serological evidence of syphilis. All reactive RPR test samples should be further tested with a treponemal test. The ASI Automated RPR Test for Syphilis for use on the ASI Evolution produces only a reactive or non-reactive result and does not report RPR titers for reactive samples. The ASI Automated RPR Test for Syphilis is for professional use only. The test is intended to be used for in vitro diagnostic testing. The ASI Evolution is intended to be used as a fully automated analyzer to objectively interpret the results of the ASI automated RPR test for syphilis. The ASI Evolution is designed to provide standardized test interpretation and to provide for storage, retrieval, and transmittal of the test results. It is intended to be acquired, possessed and used only by health care professionals. The ASI Evolution analyzer, in conjunction with the ASI Automated RPR Test is intended to be used for in vitro diagnostic testing. The ASI Automated RPR Test for Syphilis for use on the ASI Evolution produces only a reactive or non-reactive result and does not report RPR titers for reactive samples.

The ASI Evolution is an integrated digital particle analyzer designed to objectively interpret certain slide agglutination tests manufactured by Arlington Scientific, Inc. (ASI). The ASI Evolution fully automates the sample and reagent handling steps of the test procedure. Qualitative tests are performed by laboratory professionals who use the ASI Evolution to provide standardized test interpretation using criteria that define reactive and nonreactive aqqlutination reactions. The ASI Evolution employs a camera that uses light reflectance to create a highly sensitive and high-resolution image of the agglutination immunoassay. This image is then analyzed by the proprietary software algorithm to interpret the agglutination pattern. The ASI Evolution further provides tools that enable the creation, storage, retrieval and transmittal of the test results. The ASI Automated RPR Test for Syphilis reagents include the following: CARBON ANTIGEN - 0.003% cardiolipin, 0.020-0.022% lecithin, 0.09% cholesterol, charcoal (activated) as visual enhancer, phosphate buffer, 0.1% sodium azide as preservative and stabilizers. CONTROLS (REACTIVE, WEAK REACTIVE, NONREACTIVE) - Human serum or defibrinated plasma (liquid), with 0.1% sodium azide as preservative. Reagents have two-year expiration dating from date of manufacture. The specific expiration date is located on the label on the vial.

This document describes the regulatory approval for the ASI Automated RPR Test for Syphilis ASI Evolution. The product is a qualitative nontreponemal flocculation test for the detection of reagin antibodies in human serum and plasma for syphilis screening. It is designed to be used with the ASI Evolution Automated Syphilis Analyzer, which objectively interprets test results as reactive or non-reactive.

Here is a summary of the acceptance criteria and study information:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for the ASI Automated RPR Test for Syphilis ASI Evolution are based on demonstrating substantial equivalence to its predicate device, the ASI RPR Card Test for Syphilis on the ASiManager-AT. The key performance metrics are positive and negative agreement rates.

2. Sample Sizes Used for the Test Set and Data Provenance

• Prospective Samples: 1,068 individual samples. Collected at two different Departments of Public Health Labs. Data provenance is prospective.
• Retrospective Serum Samples (Agreement Study): 10 individual samples. Collected from various reference labs and serum and plasma vendors from across the United States. Data provenance is retrospective.
• Retrospective Plasma Samples (Agreement Study): 1,003 individual samples. Collected from various reference labs and serum and plasma vendors from across the United States. Data provenance is retrospective.
• ASI Evolution Characterized Specimen Testing (Clinical Diagnosis): Total of 1,068 + 1,013 = 2,081 samples (Total samples from prospective and retrospective studies)
  • Prospective Random Samples:
    • Site a: 567 Serum samples (country not specified, likely US based on other descriptions)
    • Site b: 501 Serum samples (country not specified, likely US based on other descriptions)
  • Retrospective Samples:
    • Site c: 17 Known infected samples (serum & plasma, from across the United States)
    • Site c: 996 Known uninfected samples (serum & plasma, from across the United States)
    • Total Retrospective samples: 1013
• Performance with Samples from Pregnant Women: 250 non-reactive and 30 reactive samples from pregnant women. Serum samples. Country not specified, likely US.
• Precision Testing: 10 samples (3 nonreactive, 7 reactive at various titers), each tested 192 times (total 1920 tests).
• Reproducibility Testing (7 samples): 7 samples (2 nonreactive, 5 reactive at various titers), tested at 3 sites, each sample tested 180 times across various conditions (total 1260 tests).
• Reproducibility Testing (448 samples): 448 retrospective serum samples (48 nonreactive, 400 reactive), tested at 3 sites (total 1344 tests). Samples collected from various reference labs and serum and plasma vendors from across the United States.
• Cross Reactivity/Interfering Substances: 368 samples across various categories (e.g., ANA (+), HIV (+), pregnant women, etc.).
• Carry-Over: 48 aliquots per run (24 reactive, 24 nonreactive). Run over 5 days.
• On-board Stability Testing: 4 samples (1 nonreactive, 3 reactive at various titers), each run in triplicate morning and afternoon for 5 days by 2 operators (total 120 tests).
• Frozen vs. Refrigerated Testing: Total of 55 samples (20 non-reactive, 35 reactive at various titers) tested as both frozen and refrigerated.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications

The document does not explicitly state the "number of experts" or their "qualifications" for establishing the ground truth for the test set in the comparative studies.

• For the comparative studies against the ASiManager-AT, the predicate device's results (interpreted by "trained laboratory professionals") served as the reference. These professionals are implicitly qualified by their training to interpret RPR tests.
• For the "ASI Evolution Characterized Specimen Testing," the "Expected results are based on known clinical diagnosis." This implies that clinical experts (e.g., physicians, specialists) established the diagnosis, which then served as a proxy for ground truth.

4. Adjudication Method for the Test Set

The document does not explicitly describe an adjudication method like 2+1 or 3+1. For the comparative studies, the results of the ASiManager-AT, interpreted by trained laboratory professionals, were considered the comparator. In cases of discrepancies or challenges, no specific adjudication process is detailed for these studies. For the Characterized Specimen Testing, the "known clinical diagnosis" itself serves as the ground truth, implying no further adjudication on the test results against the diagnosis.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done

No, a traditional MRMC comparative effectiveness study, where multiple human readers interpret cases with and without AI assistance to measure improvement in human performance, was not performed. The study focused on the standalone performance of the ASI Evolution device compared to the predicate device (ASiManager-AT) and known clinical diagnoses. When human operators were involved (e.g., for ASiManager-AT interpretation), they were trained professionals, but the study did not measure their improvement with AI assistance.

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

Yes, the studies primarily assessed the standalone performance of the ASI Evolution. The device is described as a "fully automated analyzer to objectively interpret the results" of the RPR test. The comparison against the ASiManager-AT (which involves human interpretation of results) and known clinical diagnoses evaluates the ASI Evolution's direct output.

7. The Type of Ground Truth Used

The ground truth used varied:

• Comparative Studies: The results obtained from the predicate device, the ASI RPR Card Test for Syphilis on the ASiManager-AT, interpreted by trained laboratory professionals, served as the comparator/reference.
• Characterized Specimen Testing: "Known clinical diagnosis" was used as the ground truth. This implies diagnoses established by medical professionals through various clinical and laboratory indicators.
• Precision, Reproducibility, Cross-Reactivity, Carry-Over, On-board Stability, Frozen vs. Refrigerated Testing: Expected results for controls and characterized samples (e.g., "RPR nonreactive," "RPR reactive 1:1 titered samples") were used as the ground truth. These expected results are typically established during the characterization and manufacturing of the control materials themselves.

8. The Sample Size for the Training Set

The document does not explicitly state the sample size used for the training set of the ASI Evolution's algorithm. It mentions that the "same proprietary interpretive algorithm used in the predicate device (ASiManager-AT) is used in the ASI Evolution." This suggests that the algorithm was developed and potentially trained using data prior to this submission, possibly with data collected for the ASiManager-AT validation. However, details of that training are not provided here.

9. How the Ground Truth for the Training Set Was Established

As the document does not specify a training set for the ASI Evolution's algorithm, it also does not detail how the ground truth for such a set was established. Given the claim that the algorithm is the "same proprietary interpretive algorithm" as in the predicate device, it is likely that the ground truth for any initial algorithm development would have been established through expert human interpretation of RPR flocculation patterns over a large set of samples, potentially correlated with confirmatory treponemal tests or clinical diagnoses.

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