Efficacy and Accuracy of Diagnosing Septic Arthritis: How Effective Are Current Methods for Timely Diagnosis of Septic Arthritis?

The diagnosis of septic arthritis requires a reliance on ancillary tests, including synovial fluid white blood cell count (jWBC), percentage of polymorphonuclear leukocytes (%PMN), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). This study evaluated these tests to determine their diagnostic utility in suspected septic arthritis. A retrospective chart review was performed on patients admitted to an urban hospital who underwent arthrocentesis. The authors evaluated the jWBC, %PMN, ESR, and CRP with receiver operating characteristic (ROC) curve analyses. Two hundred sixty-fi ve patients met inclusion criteria. Sixty-three had a culture-positive aspirate. ROC curve analysis resulted in an area under the curve (AUC) of 0.80 for jWBC with cutoff point of 22,563 cells/mm3 and an AUC of 0.71 for %PMN with cutoff point of 90.5%. CRP and ESR had AUC values of 0.62 and 0.61, respectively. The culture-positive cohort had higher elevations in all assessed diagnostic tests. However, AUC data for ESR and CRP showed little diagnostic utility. Additionally, sensitivities and specifi cities of jWBC and %PMN were too low. Associated cutoff points would result in excessive unnecessary operative intervention. Further studies should incorporate synovial fluid biomarkers into the workup of a suspected septic joint. (Journal of Surgical Orthopaedic Advances 33(2):108-111, 2024)

Key words: septic arthritis, arthrocentesis, diagnostic testing, synovial fluid biomarkers