Percentage of culture confirmation and melting curve analysis reveals false-positive Campylobacter detection in a molecular syndromic panel.

Abstract

Surveillance of enteric organisms can identify outbreaks and support control measures. The BIOFIRE FilmArray Gastrointestinal Panel (FilmArray GI) is the most common culture-independent diagnostic test (CIDT) used in Wisconsin to diagnose enteric infections. State clinical laboratories have raised concerns about inaccurate Campylobacter detection with the FilmArray GI. The Wisconsin State Laboratory of Hygiene (WSLH) evaluated the percentage of positivity and culture confirmations stratified by CIDT for Campylobacter, Salmonella, and STEC from 2018 to 2024. We further analyzed the transport time of Campylobacter specimens and the melt curves of specimens that tested positive by FilmArray GI. Campylobacter, Salmonella, and STEC specimens tested on the FilmArray GI had increases in percentage of positivity compared to those tested on other CIDTs. Salmonella and STEC specimens positive by FilmArray GI, compared to other CIDTs, had no significant culture confirmation differences. However, Campylobacter specimens positive by FilmArray GI had significantly lower culture confirmations than positive specimens from other CIDTs (62% vs. 78%; P < 0.05). Campylobacter culture confirmations were lower for FilmArray GI specimens, compared to other CIDTs, regardless of how many days the specimen spent in transport in 2023. Additionally, we found atypical melt curves among specimens positive by FilmArray GI with cultures that did not grow Campylobacter. Taken together, the higher percentage of positivity, the lower percentage of culture confirmation, and the atypical melt curves suggest that the FilmArray GI might yield false-positive Campylobacter results. These findings emphasize the importance of public health surveillance to identify potential issues with commercially available diagnostic tests.IMPORTANCEEnteric pathogens cause ~9.4 million illnesses annually in the United States. Clinical laboratories rely on culture-independent diagnostic testing platforms (CIDTs) for rapid and accurate diagnosis of enteric pathogens. Campylobacter, Salmonella, and Shiga-toxin-producing Escherichia coli (STEC) are three of the most identified enteric bacterial infections in Wisconsin. The BioFire FilmArray Gastrointestinal panel (FilmArray GI) is currently the most common CIDT used by Wisconsin clinical laboratories to diagnose Campylobacter, Salmonella, and STEC infections. However, the FilmArray GI has had notable issues and recalls in the past. Here, we used public health surveillance data to assess platform performance for these organisms. We analyzed percent positivity and culture confirmations based on testing platforms. Through our analysis, we identified potential false-positive Campylobacter results from the FilmArray GI, which were associated with atypical melt curve profiles on the BioFire platform. Public health surveillance can help identify potential issues with diagnostic platforms.