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The Diagnostic Hybrids, Inc. device, D3 Duet DFA RSV/Respiratory Virus Screening Kit, is intended for the qualitative detection and identification of respiratory syncytial virus, while screening for influenza A virus, influenza B virus, adenovirus, and parainfluenza virus types 1, 2 and 3 viral antigens, in nasal and nasopharyngeal swabs and aspirates or in cell culture. The assay detects viral antigens by immunofluorescence using monoclonal antibodies (MAbs), from patients with signs and symptoms of respiratory infection.

It is recommended that specimens found to be negative after examination of the direct specimen result be confirmed by cell culture. Negative results do not preclude influenza virus infection and should not be used as the sole basis for diagnosis, treatment or other management decisions.

Performance characteristics for influenza A virus detection and identification were established when influenza A (H3N2) and influenza A (H1N1) were the predominant influenza A strains circulating in the United States. Performance characteristics for influenza A virus detection and identification were established when influenza A H3N2 and influenza A H1N1 were the predominant influenza A strains circulating in the United States. When other Influenza A viruses are emerging, performance characteristics may vary. If infection with a novel Influenza A virus is suspected based on current clinical and epidemiological screening criteria recommended by public health authorities, specimens should be collected with appropriate infection control precautions for novel virulent Influenza viruses and sent to a state or local health department for testing. Viral culture should not be attempted in these cases unless a BSL 3+ facility is available to receive and culture specimens.

The Diagnostic Hybrids, Inc. device, D3 Duet DFA RSV/Respiratory Virus Screening Kit, uses a blend of viral antigen-specific murine MAbs. MAbs for RSV are directly labeled with R-phycoerythrin (R-PE) for the rapid detection and identification of RSV. MAbs for influenza A virus, influenza B virus, adenovirus, and parainfluenza virus types 1, 2, and 3 are directly labeled with fluorescein isothiocyanate (FITC), for rapid detection of these agents.

Kit components:

• D3 Duet DFA RSV/Respiratory Virus Screening Reagent
• Normal Mouse Gamma Globulin DFA Reagent
• Respiratory Virus Antigen Control Slides
• Wash Solution Concentrate
• Mounting Fluid

The cells to be tested, derived from a clinical specimen or cell culture, are placed onto a glass slide and allowed to air dry. The cells are fixed in acetone. The D3 Duet DFA RSV/Respiratory Virus Screening Reagent is added to the cells which are then incubated for 15 to 30 minutes at 35° to 37°C in a humidified chamber or humidified incubator. The stained cells are then washed with the diluted wash solution, a drop of the supplied Mounting Fluid is added and a coverslip is placed on the prepared cells. The cells are examined using a fluorescence microscope. The respiratory syncytial virus infected cells will fluoresce golden-yellow, while cells infected with any of the other six viruses will fluoresce apple-green. Uninfected cells will contain no fluorescence but will be stained red by the Evans Blue counter-stain. If only golden-yellow fluorescent cells are present the specimen can be reported as positive for respiratory syncytial virus antigen. If only apple-green fluorescent cells are present, the particular virus is identified using the individual reagents from the D3 Ultra DFA Respiratory Virus Screening & ID Kit (D3 Ultra) on new, separate cell preparations. If both golden-yellow and apple-green are present, the additional virus may be identified using the individual reagents from the D3 Ultra on new, separate cell preparations.

Here's a breakdown of the acceptance criteria and study details for the D' DUET DFA RSV/RESPIRATORY VIRUS SCREENING KIT:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria are not explicitly stated as numerical targets for sensitivity and specificity in the provided text. Instead, the study uses the legally marketed predicate device (D3 Ultra DFA Respiratory Virus Screening & ID Kit) as the comparator, and "100% agreement" is repeatedly cited as the performance goal versus this comparator. The device met this implicit acceptance criterion by demonstrating 100% agreement in both positive and negative percentage agreements across various virus types and specimen sources.

*IAFVBAPF123 refers to Influenza A virus, Influenza B virus, Adenovirus, and Parainfluenza virus types 1, 2, and 3.

2. Sample Sizes and Data Provenance

• Direct Fresh Specimens (Test Set):
  • Total Initial Specimens: 1203
  • Excluded Specimens: 17 (due to site deviations, duplicate specimen, insufficient cell numbers, or high background)
  • Analyzed Specimens: 1187
  • Data Provenance: Prospective, collected at three study sites in the United States.
• Cultured Specimens (Test Set):
  • Total Specimens: 298 frozen specimens
  • Data Provenance: Retrospective (frozen specimens), from a fourth study site. All specimens were derived from nasopharyngeal specimens. The age distribution of individuals is provided on page 13.

3. Number of Experts and Qualifications

The document does not explicitly state the number of experts used to establish ground truth for the test set or their specific qualifications (e.g., "Radiologist with 10 years of experience"). However, it mentions that the D3 Duet device was compared against a "cleared DSFA device" (D3 Ultra DFA Respiratory Virus Screening & ID Kit) as the comparator. This implies that the ground truth for the clinical studies was established by laboratory personnel using the predicate device, which is a standard immunofluorescence assay.

4. Adjudication Method

The document does not specify an adjudication method like 2+1 or 3+1. The results are presented as direct comparisons between the D3 Duet and the "D3 Ultra Final Identification," implying that the D3 Ultra's results served as the reference standard without further expert adjudication beyond its own established interpretation protocol.

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

No multi-reader multi-case (MRMC) comparative effectiveness study was done. This device is a diagnostic kit read by a single trained technician, not an AI system designed to assist human readers. Therefore, the effect size of human readers improving with AI vs. without AI assistance is not applicable.

6. Standalone Performance

Yes, a standalone performance study (algorithm only without human-in-the-loop performance) was done for the D3 Duet. The entire clinical performance section (pages 11-14) reports the performance of the D3 Duet device independently against the predicate device (D3 Ultra) as the gold standard.

7. Type of Ground Truth Used

The ground truth for the clinical studies was established using a cleared comparator device, specifically the D3 Ultra DFA Respiratory Virus Screening & ID Kit. This is a form of reference standard testing using an established laboratory method (immunofluorescence assay) for viral antigen detection. For the cultured specimens, cell culture methods were also employed.

8. Sample Size for the Training Set

The document does not explicitly mention a "training set" in the context of an AI/algorithm. Instead, the device is a diagnostic kit based on monoclonal antibodies. Therefore, there is no sample size for an algorithm training set. The various analytical and non-clinical performance studies (precision, detection limit, analytical reactivity, analytical specificity) act as development and validation steps for the kit itself, rather than training for an AI.

9. How Ground Truth for the Training Set Was Established

As there is no "training set" for an AI/algorithm, this point is not applicable. The development and validation of the D3 Duet kit relied on established laboratory techniques for virus isolation, identification using cell cultures, reference viral strains, and bacterial/fungal cultures. These methods served as the "ground truth" during the development and analytical validation of the antibody blend and assay performance.

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The PathoDx Respiratory Virus Panel (RVP) kit is a direct immunofluorescence test for the qualitative detection of 7 common respiratory viruses (respiratory syncytial virus, influenza A, influenza B, parainfluenza viruses 1,2, and 3, and adenovirus) in prepared direct patient specimens and following growth in cell culture. The materials supplied are intended for in vitro use only.

Direct immunofluorescence test for the qualitative detection of seven common respiratory viruses.

The PathoDx Respiratory Virus Panel kit consists of one screening reagent containing monoclonal antibodies to each respiratory virus and seven virus-specific monoclonal antibody reagents. All reagents contain monoclonal antibody labeled with fluorescein. Acetone-fixed cells from either patient specimens or cell culture are stained with the Screening Reagent and the Negative Control Reagent. The Screening Reagent contains fluorescein-labeled monoclonal antibodies to RSV, influenza A. influenza B. parainfluenza viruses 1, 2, and 3, and adenovirus. They will react specifically to any of the above viral antigens, if present in the cell. The Negative Control Reagent contains fluorescein-labeled murine antibodies which do not react with the viral agents. Unbound antibody and Evans blue counterstain are washed off with buffered saline, and the slide is mounted with buffered glycerol. Under fluorescence microscopy, the viral antigens recognized by the monoclonal antibodies present will show a characteristic apple-green fluorescence, while uninfected cells will counterstain red with Evans blue. To identify which of the seven respiratory viruses is reactive with the Screening Reagent, acetonefixed cell preparations are stained with each of the seven virus-specific reagents, washed free of unbound antibody, mounted with buffered glycerol, and observed under fluorescence microscopy. The responsible virus(es) will show characteristic apple-green fluorescence with uninfected cells counterstaining red.

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

The document does not explicitly state pre-defined acceptance criteria in terms of specific sensitivity, specificity, or agreement percentages. Instead, it presents the device's performance in comparison to reference methods and a predicate device. Based on the provided clinical performance data, the following table summarizes the device's performance:

Table of Device Performance

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

• Clinical Site 1, Study 1 (Direct Smear & Shell Vial):
  • Test Set Size: 200 specimens (150 fresh, 50 retrospective).
  • Data Provenance: Midwestern United States, a mix of prospective (fresh) and retrospective samples.
• Clinical Site 1, Study 2 (Cell Culture Isolates):
  • Test Set Size: 168 retrospective, frozen cell culture isolates (29 negative, 139 positive).
  • Data Provenance: Midwestern United States, retrospective.
• Clinical Site 2 (Direct Smear & Shell Vial):
  • Test Set Size: 185 fresh specimens (174 for direct smear, all 185 for shell vial).
  • Data Provenance: Midwestern United States, prospective.

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. The ground truth appears to be established by definitive cell culture procedures or comparison against predicate devices ("Kit A" and "Kit B"), which themselves represent established diagnostic methods.

4. Adjudication method for the test set

The document does not describe a formal adjudication method (e.g., 2+1, 3+1). The "ground truth" for the PathoDx device's direct smear performance in Clinical Site 1, Study 1, was definitive cell culture. For comparisons against predicate devices, "agreement" percentages are reported, implying direct comparison without an explicit adjudication process beyond the standard interpretation inherent in each method. For PathoDx direct smear versus cell culture, disagreements were individually detailed (e.g., 17 specimens negative by PathoDx but positive by cell culture were identified with specific viruses).

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

A multi-reader multi-case (MRMC) comparative effectiveness study involving human readers and AI assistance was not performed. This device is a diagnostic immunoassay kit, not an AI-powered image analysis tool for human readers.

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

This question is not directly applicable as the PathoDx Respiratory Virus Panel is a direct immunofluorescence test kit, requiring human interpretation of fluorescence microscopy results. It is not an algorithm-only device. The performance data presented is for the test kit itself, which inherently involves human technicians performing the test and interpreting the results.

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

The primary type of ground truth used was:

• Definitive Cell Culture Procedure: This was explicitly used as the reference standard for evaluating the PathoDx direct smear performance in Clinical Site 1, Study 1.
• Predicate Device Results (Kit A and Kit B): For many comparisons, the results obtained from "Kit A" and "Kit B" (Bartels Viral Respiratory Screening and Identification Kit and Light Diagnostic Respiratory Viral Screen Indirect Immunofluorescence Assay by Chemicon International, Inc., respectively) served as the comparator or "reference" for calculating agreement. These predicate devices are themselves established diagnostic methods.

8. The sample size for the training set

The document does not mention a distinct "training set" for the PathoDx Respiratory Virus Panel. As a diagnostic reagent kit, its development would typically involve assay optimization and validation during manufacturing, rather than a machine learning-style training phase with a specific labeled dataset. The clinical studies described are for performance evaluation.

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

Since no specific "training set" is mentioned in the context of machine learning, this question is not applicable. The development of such diagnostic kits relies on established virological principles, antibody specificity validation, and optimization of assay parameters, rather than ground truth establishment for a training dataset.

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