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The FebriDx® Bacterial/Non-Bacterial Point-of-Care Assay is a qualitative visually read rapid immunoassay for the detection of human host response proteins, Myxovirus resistance protein A (MxA) and C-reactive protein (CRP) directly from fingerstick blood. FebriDx is indicated for use in patients aged 12-64 who present to urgent care or emergency care settings for evaluation of acute respiratory infection who have had symptoms for less than 7 days and within 3 days of fever onset.

FebriDx test results are intended to be used in conjunction with other clinical and diagnostic findings as an aid in the diagnosis of bacterial acute respiratory infection and differentiation from non-bacterial etiology. The assessment of whether a bacterial infection is present should always be based on consideration of all available information, and not based solely on the FebriDx test results. FebriDx test results are not intended to identify a specific pathogen or the severity of infection.

FebriDx External Controls are used in the FebriDx Test as assayed quality control samples to assess the performance and reliability of the FebriDx Test.

FebriDx is a rapid lateral flow immunoassay for the visual, qualitative, in vitro detection of elevated levels of host response proteins, Myxovirus resistance protein A (MxA) and Creactive protein (CRP), directly from fingerstick blood to aid in the evaluation of acute respiratory infections. The single-use, disposable FebriDx test is an all-in-one integrated platform that includes a lateral flow test strip, a built-in retractable safety lancet, blood collection and transfer tube and buffer delivery system. The FebriDx test produces a visualread qualitative result. Operators interpret the test and can visually see whether the infection may be due to a bacterial infection or other non-bacterial etiology.

FebriDx External Controls to monitor performance and reliability of the FebriDx test are sold separately. FebriDx External Controls are a two-vial set with one negative buffer and one positive control containing recombinant CRP and MxA.

The Lumos Diagnostics FebriDx Bacterial / Non-bacterial Point-of-Care Assay is a qualitative visually read rapid immunoassay designed to detect human host response proteins (Myxovirus resistance protein A (MxA) and C-reactive protein (CRP)) from fingerstick blood. It is intended for use in patients aged 12-64 with acute respiratory infection symptoms for less than 7 days and within 3 days of fever onset, presenting to urgent care or emergency care settings. The assay aids in diagnosing bacterial acute respiratory infection and differentiating it from non-bacterial etiology, to be used in conjunction with other clinical and diagnostic findings.

Here's an analysis of the acceptance criteria and the study proving the device meets them:

1. Table of Acceptance Criteria and Reported Device Performance

The provided document does not explicitly state pre-defined acceptance criteria for the clinical performance. However, regulatory bodies typically look for high Positive Percent Agreement (PPA) and Negative Percent Agreement (NPA) to establish substantial equivalence. Based on the clinical study results, the following can be inferred as performance benchmarks.

Note: For microbiologically confirmed bacterial infections, the PPA increased to 100% (33/33) and NPA improved to 91.0% (263/289).

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

• Test Set (Clinical Study):
  • Symptomatic Participants (ARI cohort): 520 participants.
  • Asymptomatic Controls: 170 participants (160 for the NPA analysis).
  • Total Enrolled: 708 participants (520 symptomatic, 170 asymptomatic, 18 withdrawals after consent).
• Data Provenance: The study was a "well-controlled, prospective, multi-center blinded clinical trial conducted in the United States (U.S.)" between October 2019 and April 2021.

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

• Number of Experts: Two independent expert reviewers.
• Qualifications: The document states they were "two independent expert reviewers" but does not explicitly detail their specific qualifications (e.g., "radiologist with 10 years of experience"). However, given the nature of the study (diagnosis of bacterial acute respiratory infection), it can be inferred they are likely medical professionals with expertise in infectious diseases, emergency medicine, or urgent care.

4. Adjudication Method for the Test Set

The adjudication method was based on a "composite Clinical Reference Algorithm" in conjunction with "adjudication by two independent expert reviewers, who were blinded to FebriDx results." This suggests a consensus-based approach where the experts reach a final decision after reviewing all available clinical and laboratory testing data.

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 conducted. The clinical study evaluated the standalone performance of the FebriDx device against a clinical reference algorithm and expert adjudication. It did not involve comparing human readers with and without AI assistance.

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

• Yes, a standalone performance study was conducted. The "Clinical Performance" section directly assesses the FebriDx device's accuracy (PPA, NPA, etc.) against the adjudicated clinical truth. The device itself is a visually-read rapid immunoassay, implying a human reads the result, but the assessment of its diagnostic accuracy is the "standalone" performance of the assay itself compared to the ground truth. The study reports the performance characteristics of the device's output.

7. The Type of Ground Truth Used

The ground truth, referred to as "Final diagnosis (Clinical Truth)," was based on:

• A composite Clinical Reference Algorithm which incorporated:
  • Pathogen detection testing (e.g., bacterial culture, multiplex PCR for various viruses/bacteria, SARS-CoV-2 PCR, EBV IgM).
  • Measures of host immune response (e.g., Hematology: Complete Blood Cell Count (CBC), B.R.A.H.M.S Procalcitonin).
• Adjudication by two independent expert reviewers who were blinded to the FebriDx results and made a final qualitative diagnosis after review of all clinical and laboratory testing data.
• Outcomes data: Participants admitted to the hospital for pneumonia with objective evidence of bacterial infection were reclassified, indicating that outcomes were a component of confirming or revising the "clinical truth."

8. The Sample Size for the Training Set

The document does not provide information regarding the sample size used for the training set. The descriptions focus on the analytical performance (precision, LoD, hook effect, stability) and the clinical study which serves as the validation/test set for regulatory submission.

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

Since information on a distinct "training set" is not provided, the method for establishing its ground truth is also not specified in this document. It is common for such devices to use internal development or historical data for training, and the clinical study described is the primary validation performed for regulatory submission.

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