# Diagnostic performance of broad-range PCR in bacterial peritonitis

## TL;DR

This study compares a new molecular test to traditional methods for diagnosing bacterial peritonitis, finding the new test detects more infections and identifies more bacteria.

## Contribution

The study introduces and evaluates Molecular Culture ID, a broad-range PCR assay for diagnosing bacterial peritonitis with higher sensitivity and broader bacterial detection.

## Key findings

- Molecular Culture ID detected 1.6x more positive samples than standard culture methods.
- The assay identified 289 additional bacterial species, particularly anaerobes that are hard to culture.
- Molecular Culture ID results correlated well with high leukocyte counts, a sign of infection.

## Abstract

Bacterial peritonitis (BP) is a serious complication commonly associated with cirrhosis and ascites, often leading to high mortality rates. Although these effects could be reduced with timely and appropriate antibiotics, traditional BP diagnosis relies on culture, often delaying targeted treatment. Therefore, the use of fast molecular assays holds the potential to enhance laboratory diagnosis. In this study, we assessed the diagnostic performaance of Molecular Culture ID, a broad PCR-based assay targeting the 16S-23S interspace rDNA region in the scope of BP diagnosis.

The residual material from 247 peritoneal fluid samples submitted for routine diagnostics was analyzed using Molecular Culture ID and compared alongside the standard of care (SOC) results.

Sample positivity and species identification outcomes of Molecular Culture ID were compared to those of SOC. Molecular Culture ID yielded 1.6x more positive samples than SOC. Percent positive agreement (PPA) between Molecular Culture ID and SOC at the sample level was 90.1% (IC 95%, 81.0% to 95.1%), and negative percent agreement (NPA) was 70.5% (IC 95%, 63.3% to 76.7%). At the species level, the PPA was 75.2% (95% CI 67.2% to 81.8%). Molecular Culture ID yielded 289 extra bacterial identifications, mainly anaerobic species. High leukocyte counts, indicative of infection, were concordant with Molecular Culture ID positivity.

Molecular Culture ID demonstrated enhanced BP diagnostic capabilities compared to SOC, with higher positivity rates, more comprehensive species identification for difficult to culture species and a high correlation with leukocyte counts.