The diagnostic accuracy of inflammatory blood markers for purulent flexor tenosynovitis

Purpose For patients with purulent flexor tenosynovitis, our purpose was to (1) calculate the diagnostic accuracy of white blood count (WBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) for those who underwent surgical drainage, (2) to correlate these markers for those treated with antibiotics alone, and (3) to evaluate the accuracy of diagnosis for surgical patients. Methods A total of 82 consecutive patients (71 surgical and 11 nonsurgical) with flexor tenosynovitis were identified from orthopedic databases at 2 academic centers. We evaluated inflammatory markers (WBC, ESR, and CRP), radiographs, descriptions of surgical findings, and intraoperative cultures for all patients. For nonsurgical patients, we evaluated inflammatory markers for possible correlation with the presumed diagnosis of purulent flexor tenosynovitis. For surgical patients, sensitivity, specificity, positive predictive value, and negative predictive value were calculated individually for inflammatory markers. Results For nonsurgical patients, WBC, ESR, and CRP were elevated in 3 of 11 patients (27%), 6 of 8 patients (75%), and 6 of 7 patients (86%), respectively. For surgical patients, the intraoperative findings or cultures were consistent with infection in 69 of 71 cases (97%), whereas calcific tendinitis was diagnosed in 2 cases. Cultures were positive in 56 patients (79%). All 3 markers had a specificity and positive predictive value of 100%. For WBC, ESR, and CRP, respectively, the sensitivity was 39%, 41%, and 76% and the negative predictive value was 4%, 3%, and 13%. Conclusions Commonly used inflammatory blood markers (WBC, ESR, and CRP) may be helpful in diagnosing purulent flexor tenosynovitis. If the levels of any of these markers are elevated in patients suspected of having the diagnosis, the likelihood of infection is extremely high. However, with low negative predictive values, these markers cannot reliably rule out infection. Type of study/level of evidence Diagnostic III.