The additional value of multiplex PCR in differential diagnostics of PJI - a retrospective analysis

Fragestellung Differential diagnostics of periprosthetic joint infection (PJI) remains a major clinical challenge in orthopedic surgery. Correct and fast pathogen detection is a key factor for the targeted antibiotic therapy and successful treatment. Alongside the standard procedures, including blood samples and joint aspiration for cytometrie and microbiology, and the use of serum and aspirate biomarkers, nucleic acid amplification techniques (NAT) have shown promising results to enhance the diagnostics. The Unyvero ITI system offers a multiplex PCR analysis for pathogens commonly associated with PJI, however the analysis is quite costly, and the additional costs are not covered by the german DRG hospital reimbursement system. Sensitivity and specificity can match those of other techniques, but it generates a result within a few hours. If this can actually lead to a faster and more accurate antibiotic therapy or other consequences in therapeutic treatment is not know, nor is there any guideline on which patients might profit from the additional analysis in PCR.

Methodik We performed a retrospective analysis of over 300 cases of revision arthroplasty where PCR was employed to find out which patients actually benefitted from the analysis, to assess the medical advantage for those patients as well as the possible economic benefit for the treating instituion. We focused on those cases whre only PCR detected a pathogen and on cases where positive PCR gave faster results than conventional microbiology, as well as changes in antibiotic treatment due to the results of the PCR, and possibly faster targeted treatment.

Ergebnisse und Schlussfolgerung Medium sensitivity (67 %) and high specificity (95 %) of the multiplex PCR in our analysis matched the rates already published in the literature. On average, the results of PCR were available 2.7 days earlier than those of conventional culture, but adaptation of the antibiotic treatment due to the PCR result from an empiric to a calculated therapy was rare, therefore most of the positive PCR results and no direct therapeutic consequence. 21 out of 131 positive cases were positive only in the PCR, with Cutibacterium acnes being the most frequently detected pathogen in these cases and some with previous antibiotic treatment; In these cases, the PCR analysis added significantly to targeted treatment. Still, the “Number needed to diagnose” remains high.

We found no significant difference in economic parameters, such as length of stay or number of revision surgeries in patients with positive PCR results, as opposed to those where the PCR did not detect the pathogen.

Nucleic acid testing systems certainly can add to the diagnostic portfolio in revision arthroplasty, with no other risk but an economic one associated with their use. Their true impact on therapeutic decisions in daily routine is limited, and use should be restricted to critical cases only.

Stichwörter periprosthetic joint infection; PCR; molecular biology; NAT

Publication History

Article published online:
15 October 2020