# P-142. Benefits and Pitfalls of Multiplex Gastrointestinal Polymerase Chain Reaction testing in a Veterans Affairs Hospital

## TL;DR

This study evaluates the accuracy of a rapid PCR test for detecting gastrointestinal pathogens in veterans, finding it effective for some but with false positives for others.

## Contribution

The study provides empirical evidence on the performance of GI PCR testing in a VA hospital, highlighting its benefits and limitations in clinical practice.

## Key findings

- The Biofire GI PCR test showed high sensitivity for Campylobacter but had a significant rate of false positives for Norovirus and Vibrio.
- Only 58% of Norovirus-positive samples were confirmed by LabCorp testing, indicating potential overdiagnosis.
- Vibrio results were not confirmed by culture, suggesting limitations in the test's reliability for this pathogen.

## Abstract

In the US infectious gastroenteritis remains a significant cause for morbidity and a public health concern. While stool culture had been the standard tool for microbiological diagnosis, known for its time consuming and often lower yields, rapid diagnostic tests have now been developed. Multiplex gastrointestinal (GI) polymerase chain reaction (PCR) testing is commercially available as a rapid, sensitive method for detecting GI pathogens, bacteria, viruses, and parasites in a single stool sample. Nevertheless, challenges in interpreting results can appear especially in mixed infections where detections may not be clinically significant. While high sensitivity of testing is desirable, false positive results require careful interpretation. We reviewed the performance of GI PCR tests in our facilityTable 1GI PCR resultsTable 2GI PCR COINFECTIONS

GI PCR results

GI PCR COINFECTIONS

Retrospective chart review from 2021 to 2024 of US Veterans at Northport Veteran Affairs Medical Center who had positive results on Biofire® FilmArray GI PCR. We focused on norovirus, Campylobacter and Vibrio results. Norovirus positive specimens were sent to LabCorp reference laboratory. Campylobacter results were compared to culture from Campylobacter selective agar plate. Vibrio and Salmonella spp results were sent for confirmation to our local department of health

111 GI PCR results were reviewed. The median age of the patients was 75 years (27-96). 8 were women. 64% Caucasian, 12% Black, 12% Hispanic. Table 1 lists the PCR results, Table 2 the coinfections. Of the 15 Campylobacter positive results, culture was done in 8 and cultured in 5. All 3 Vibrio results were not confirmed by culture. The 1 Salmonella result was confirmed as non-typhi. Of the 2 Yersinia results, one was cultured and was confirmed. Of the 93 Norovirus results, 52 were tested at LabCorp, 30 (58%) were negative. Genogroup II was most common (36%)

A significant percentage of our Biofire GI PCR Norovirus positive results were false positive. Also, the Vibrio results were not reliable. On the other hand, it was more sensitive for Campylobacter. While the Biofire GI PCR is a valuable tool for detecting several gastrointestinal pathogens, it is important to be aware of the potential for false positive Norovirus and Vibrio results and to use clinical judgment and confirmatory testing when appropriate

All Authors: No reported disclosures