For patients who underwent revision shoulder arthroplasty, preoperative measurement of synovial fluid interleukin-6 levels was more sensitive and specific compared with current preoperative testing for predicting positive cultures, according to study results.
From November 2012 to September 2013, researchers prospectively enrolled 32 consecutive patients evaluated for pain at the site of a shoulder arthroplasty to undergo revision surgery. On the basis of objective preoperative and intraoperative findings, the researchers categorized cases into infection and no-infection groups and also enrolled 20 patients treated with arthroscopic rotator cuff repair to serve as a non-infected control group.
The researchers obtained synovial fluid through aspiration intraoperatively for all patients and preoperatively for some patients. Cytokine immunoassay that utilized electrochemiluminescent detection was used to measure synovial fluid interleukin-6 (IL-6) levels, and a receiver operating characteristic curve was used to determine the diagnostic utility of synovial fluid IL-6 analysis.
Receiver operating characteristic curve analysis showed an area under the curve of 0.891 for synovial fluid IL-6 measurement, with an ideal cutoff value of 359.3 pg/mL. Results showed a sensitivity of 87%, specificity of 90%, positive likelihood ratio of 8.45 and negative likelihood ratio of 0.15.
Although the researchers found negative results on standard perioperative testing — including the erythrocyte sedimentation rate and C-reactive protein levels — in seven patients, there were multiple positive intraoperative tissue cultures. In five of the seven patients, the researchers found elevated levels of synovial fluid IL-6, with a median value of 1,400 pg/mL.
According to study results, preoperative IL-6 synovial fluid values and frozen section histologic findings correlated well with intraoperative synovial fluid IL-6 values. Patients with Propionibacterium acnes infection also had significantly elevated synovial fluid IL-6 levels, according to the researchers. – by Casey Tingle
Disclosure: Frangiamore has no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.