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The Sofia 2 Lyme FIA employs immunofluorescence for the rapid differential detection of human IgM and IgG antibodies to Borrelia burgdorferi from finger-stick whole blood specimens from patients suspected of B. burgdorferi infection of at least 2 weeks' duration. The Sofia 2 Lyme FIA is intended for use as an aid in diagnosis of Lyme disease. A negative result does not preclude infection with B. burgdorferi. Positive results must be confirmed by testing with a corresponding second-tier B. burgdorferi Western blot assay. Test results are to be used in conjunction with information obtained from the patient's clinical evaluation and other diagnostic procedures. The assay is to be performed on the Sofia 2 instrument. Professional guidelines should be consulted regarding testing and treatment for Lyme disease when acute B. burgdorferi infection is suspected.

The Sofia Lyme Control Set is intended for use as assayed quality control materials to verify the performance of the Sofia Lyme FIA and Sofia 2 Lyme FIA test system.

The Sofia 2 Lyme FIA is an immunofluorescence-based, lateral flow assay for detection of IgM and/or IgG antibodies to Borrelia burgdorferi in patient specimens. Reagents for the assay are ready-to-use and provided in the kit. The assay uses a bidirectional test strip format to detect both IgM and IgG antibodies to B. burgdorferi. One side of the test strip detects IgM antibodies to B. burgdorferi and the other side of the test strip detects IgG antibodies to B. burgdorferi. To perform the test, the patient finger-stick whole blood specimen is obtained with the provided Capillary Tube (a.k.a. whole blood separator device). The Capillary Tube stands or is held vertically to allow the blood to drain. This device separates the red blood cells from the whole blood specimen using a gravimetric flow through a sample pad coated with rabbit anti-human red blood cell (RBC) antibodies. The user dispenses all of the Reagent Solution into the Reagent Tube and inserts the Capillary Tube into the Reagent Tube and shakes the tube vigorously. Two drops of diluted sample are dispensed into the round sample well located near the center of the Test Cassette. The Test Cassette is loaded into Sofia 2 in either the READ NOW Mode or WALK AWAY Mode. In READ NOW Mode, the user allows the cassette to develop on the countertop for 15 minutes. In WALK AWAY Mode, the user immediately after adding the specimen to the cassette, the cassette is inserted into Sofia 2. Sofia 2 will analyze the test strip at 3, 5, 8, 10, and 15 minutes until both IgM and IgG positive results are received. This feature allows for earlier read times. Each Sofia 2 Lyme FIA kit will contain one Positive and one Negative Control—each provided in separate dropper bottles. The external controls will be provided separately as well in a Sofia Lyme Control Set. The Positive and Negative QC controls are formulated with patient Lyme IgM and IgG positive serum that are diluted into 1X PBS and 0.3% Microcide is added to the solution as an antimicrobial. The External Controls will be tested by adding 2 drops to the test cassette.

Here's a breakdown of the acceptance criteria and study information for the Sofia 2 Lyme FIA device, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The document doesn't explicitly state "acceptance criteria" in a single table, but rather presents performance data that would be used to demonstrate these criteria. Based on the "Substantial Equivalence Information" and "Performance Data" sections, the implied acceptance criteria are comparable performance to the predicate devices (Vidas Lyme IgM and Vidas Lyme IgG) in terms of precision, reproducibility, analytical specificity, clinical sensitivity, and method comparison (PPA and NPA).

Since specific numerical acceptance thresholds are not provided, the table below summarizes the reported performance values that are implicitly demonstrating compliance with "good" or "comparable" performance.

Notes on Inconsistencies: There is a minor inconsistency in the "Precision – Within Run" table for IgG Low Positive (C95) results. The "Run 2" column shows 46/48 (95.8%), while the "Total (n=96)" shows 100%. This might be a typo in the table, or the "Total" is derived differently.

2. Sample Size and Data Provenance

• Precision and Reproducibility:

  • Sample Size: Contrived samples. For precision, 96 tests per sample level (48 in Run 1, 48 in Run 2). For reproducibility, 30 tests per sample level per site (total 90 tests per sample level across 3 sites).
  • Data Provenance: Not explicitly stated, but "Contrived samples were prepared" suggests laboratory-generated, possibly in the US (Quidel site).

• Matrix Equivalency:

  • Sample Size: 321 patients
  • Data Provenance: "A field study was conducted." Location not specified, but likely within the US.

• CDC Reference Panel:

  • Sample Size: IgM: 190 Negative Controls, 60 Early Lyme EM Positive, 30 Late Lyme. IgG: 190 Negative Controls, 60 Early Lyme EM Positive, 30 Late Lyme.
  • Data Provenance: CDC Reference Panel (implies US government source).

• Specificity Study:

  • Sample Size: 200 samples (100 endemic, 100 non-endemic).
  • Data Provenance: Samples "obtained from asymptomatic (healthy, normal) populations in both endemic and non-endemic regions." Regions are not specified.

• Sensitivity Study:

  • Sample Size: 95 "well-characterized clinically or culture confirmed Lyme disease samples."
  • Data Provenance: Not explicitly stated, but described as "well-characterized clinically or culture confirmed Lyme disease samples."

• Method Comparison (Clinical Study):

  • Sample Size: Total 326 samples for IgM (62 Positive, 29 Equivocal, 233 Negative by Predicate). Total 324 samples for IgG (54 Positive, 270 Negative by Predicate).
  • Data Provenance: "prospectively collected specimens from subjects suspected of having Lyme disease." Country of origin not specified, but typically US for FDA 510(k) submissions unless stated otherwise.

3. Number of Experts and Qualifications for Ground Truth

• The document does not specify the number of experts used or their qualifications for establishing ground truth for the test set samples in any of the clinical or specificity/sensitivity studies.
• For the CDC Reference Panel, the panel itself implies expert consensus or well-established diagnostic criteria as its ground truth, but the individual experts involved are not mentioned.
• For the Sensitivity Study, "well-characterized clinically or culture confirmed Lyme disease samples" implies diagnosis by medical professionals following established guidelines, but specific expert details are absent.

4. Adjudication Method for the Test Set

• The document does not explicitly mention any adjudication method (e.g., 2+1, 3+1) for resolving discrepancies in the test set's ground truth determination. Ground truth is inferred primarily from clinical diagnosis, culture confirmation, or established reference panels/predicate assays.

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

• No, a MRMC comparative effectiveness study was not explicitly described. The studies focus on the analytical and clinical performance of the device itself, and its comparison to predicate devices, rather than a study evaluating improvement in human reader performance with or without AI assistance. The device is an automated immunofluorescence assay (FIA), not an AI-assisted diagnostic imaging or interpretation tool.

6. Standalone Performance

• Yes, standalone performance was done. The entire "Performance Data" section (sections a-j) describes the performance of the Sofia 2 Lyme FIA algorithm/device in a standalone capacity, without human interpretation of the results to establish the initial diagnosis. The device's output (positive/negative) is directly compared to various ground truth standards.

7. Type of Ground Truth Used

The types of ground truth used vary by study:

• Precision/Reproducibility: Contrived samples (known concentrations/status).
• Matrix Equivalency: Clinical diagnosis based on patient outcome or other diagnostic procedures (implied by comparing finger-stick whole blood to serum/plasma, which are standard clinical samples).
• CDC Reference Panel: "Clinical Status" (established by CDC, likely involving clinical diagnosis and confirmed lab results) and "Western Blot" (a gold standard serological confirmation for Lyme disease).
• Specificity Study: Asymptomatic/healthy status from endemic and non-endemic populations.
• Sensitivity Study: "Well-characterized clinically or culture confirmed Lyme disease samples."
• Method Comparison: Predicate assays (Vidas Lyme IgM and IgG) as a benchmark, and second-tier Western Blot for confirmation of first-tier positive or equivocal results.

8. Sample Size for the Training Set

• The document does not explicitly state the sample size used for a "training set." This device is an immunoassay, not a machine learning or AI model in the typical sense that requires a training set of images or data for algorithm development. The "Assay Cutoff" study mentions establishing cutoffs, which is an optimization process, but not a "training set" in the context of deep learning.

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

• Given that a specific "training set" for an AI/ML model is not described, the method for establishing its ground truth is not applicable/not provided. The "Assay Cutoff" study involved testing "matched finger-stick whole blood, serum and plasma samples with the aim of setting the whole blood assay cutoff so that the clinical performance... is statistically similar to the FDA cleared Sofia Lyme FIA serum and plasma assay." This suggests that the ground truth for establishing cutoffs was based on a combination of clinical performance (likely against a known diagnosis or reference method) and comparison to an already cleared device.

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