Clinical utility of 16S ribosomal ribonucleic acid gene polymerase chain reaction versus tissue culture in shoulder periprosthetic joint infections.

BACKGROUND: Diagnosing shoulder periprosthetic joint infection remains challenging, particularly in the setting of indolent organisms. Broad-range 16S ribosomal ribonucleic acid (RNA) gene polymerase chain reaction (PCR) with sequencing has been proposed as an adjunct to culture; however, its diagnostic performance in revision shoulder arthroplasty using periprosthetic tissue remains incompletely defined. METHODS: Single center retrospective study of revision shoulder arthroplasty cases in which both intraoperative periprosthetic tissue cultures and broad-range 16S rRNA gene PCR with sequencing were obtained which is routine at the study center. Five deep periprosthetic tissue specimens from the glenoid and/or humeral bone-implant interfaces were cultured aerobically and anaerobically for a minimum of 14 days. For molecular testing, 5 tissue specimens were pooled and homogenized prior to automated DNA extraction, real-time PCR amplification, sequencing, and organism identification using SmartGene IDNS. The microbiologic reference standard for infection was defined as classified by the 2018 International Consensus Meeting (ICM). Diagnostic performance of 16S PCR was calculated relative to this reference. Agreement between 16S PCR and culture was assessed using Cohen κ. RESULTS: Fifty-nine revision cases were included; 18 met the 2018 ICM criteria for infection and 41 were classified as not infected. Relative to the ICM-confirmed causative organism, 16S PCR yielded 0 true positives, 18 false negatives, 6 false positives, and 35 true negatives. Sensitivity was 0.0%, specificity was 85.4%, positive predictive value was not calculable (no true positives identified), negative predictive value was 66.0%, and overall accuracy was 59.3%. Overall agreement was 66.1% with only slight chance-corrected agreement (Cohen κ = 0.087). CONCLUSION: In this shoulder-specific cohort, 16S rRNA gene PCR demonstrated low observed sensitivity, poor organism-level concordance with tissue culture, and limited clinical utility. Routine use of 16S PCR in revision shoulder arthroplasty cannot be supported based on the findings of the present study. Its role may be limited to select cases with high clinical suspicion and negative bacterial cultures, though further prospective study is needed.