Home News CRP had highest diagnostic utility for infection during two-stage exchange

CRP had highest diagnostic utility for infection during two-stage exchange


August 17, 2022

1 min read



Seetharam A, et al. Paper 951. Presented at: Musculoskeletal Infection Society Annual Meeting; Aug. 5-6, 2022; Pittsburgh (hybrid meeting).

Seetharam reports no relevant financial disclosures.

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In diagnosing periprosthetic joint infection during two-stage exchange, results showed C-reactive protein had the highest diagnostic utility, while erythrocyte sedimentation rate and synovial biomarkers had acceptable diagnostic utility.

“We know that appropriate diagnosis of [periprosthetic joint infection] PJI before reimplantation is going to be critical for long-term success, so the more we can do to find out how we can accurately diagnose these will help us prevent failure down the road,” Abhijit Seetharam, MD, a fourth-year resident at Indiana University School of Medicine, said in his presentation at the Musculoskeletal Infection Society Annual Meeting.

Seetharam and colleagues retrospectively reviewed serum and synovial aspiration data of about 250 patients who underwent two-stage exchange with antibiotic spacers for PJI of the hip or knee. Seetharam noted serum and synovial data collected included erythrocyte sedimentation rate (ESR), CRP, white blood cell count, polymorphonuclear percentage, neutrophil-to-lymphocyte ratio and absolute neutrophil count.

“We separated our patients into two cohorts, a PJI and then a non-PJI cohort, and that was determined by if they had positive cultures or the presence of a sinus tract,” Seetharam said.

For serum markers, Seetharam noted CRP had the highest receiver operating characteristic (ROC) curve and area under the curve, with a diagnostic threshold of 3.1 mg/dL, a sensitivity of 65% and a specificity of approximately 79%. He added ESR also had an acceptable AUC.

“Looking at these in a head-to-head comparison, we found that serum CRP significantly outperformed all of the other markers that we looked at, but none of the other serum markers were significantly better than any of the others,” Seetharam said.

When looking at the change in percentage from when a patient first presented with a PJI to the final ESR or CRP test before reimplantation, Seetharam noted serum ESR and serum CRP had AUCs around 0.6, making these poor diagnostic markers.

“Getting into our synovial markers, you can see the ROC curves had no real outperformance or standout from any others,” Seetharam said. “Putting those into a table format, all the AUCs, right around 0.75, are acceptable for diagnostic performance, but there was no one synovial test that outperformed any of the others in our analysis.”

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