Diagnostic utility of laboratory tests in septic arthritis

Abstract

Background: Septic arthritis remains a challenging diagnosis in which the doctor often relies on laboratory tests. Objective: To examine the diagnostic utility of three ancillary tests-namely, white blood cells (WBC), erythrocyte sedimentation rate (ESR) and the WBC in the joint fluid (jWBC)-using likelihood ratios (LRs) and receiver operating characteristic (ROC) curves. Methods: This was a retrospective cohort study at the Jacobi Medical Center. Medical charts of patients who had undergone arthrocentesis were included. Patients who had ''dry taps'' were excluded from the study. Patients were considered to have septic arthritis if they had a positive arthrocentesis culture or operative findings. The primary outcomes of this study were the sensitivities, specificities, LR(+) and LR(2) values of the laboratory tests for septic arthritis. The performance characteristics of the laboratory tests were analysed using ROC curves. Results: 156 patients were enrolled, 16 (10%) had septic arthritis. The sensitivities for WBC, ESR and jWBC were 0.75, 0.75 and 0.50, and the specificities were 0.55, 0.11 and 0.88, respectively. The LR(+) values were 1.7, 0.84 and 4.0, and the LR(2) values were 0.46, 2.4 and 0.57, respectively. In ROC curve analysis, jWBC was the best test (area under the curve (AUC) 0.75, 95% confidence interval (CI) 0.58 to 0.92), followed by WBC (AUC 0.69, 95% CI 0.57 to 0.80) and ESR (AUC 0.55, 95% CI 0.37 to 0.74). A cut-off of jWBC = 17 500 maximised sensitivity and specificity on the ROC curve. Conclusions: jWBC was the best diagnostic test for septic arthritis, WBC and ESR were poor tests. However, no test was diagnostic, and the clinician must be careful with patients with a potential septic joint.

The Mark Coventry Award: Diagnosis of Early Postoperative TKA Infection Using Synovial Fluid Analysis

“…If the threshold for diagnosing infection was decreased to greater than 10,700 cells/lL, the NPV increased to 99%, but the PPV was reduced to 62%. Interestingly, the WBC counts we observed in the acute postoperative period were nearer to those in septic arthritis of native knees [14]. Tests for %PMN and CRP were less valuable in diagnosing early infection, but both tests' optimal thresholds demonstrated high NPV (97% and 91%, respectively) and could potentially be used to rule out infection but are less useful in diagnosing infection.…”

Hematogenous Septic Ankle Arthritis

“…The value of laboratory examinations in the diagnosis of septic arthritis remains uncertain, especially for peripheral white blood cell count [4,9]. Synovial fluid analysis for cell count, Gram stain, and culture is the fundamental diagnostic tool for septic arthritis [15].…”

Fluxograma diferencial entre a artrite séptica e sinovite transitória do quadril em crianças

“…[18][19][20] In the joint aspiration it is necessary, besides the direct analysis of the material, to evaluate the presence of leukocytes which usually results in a count above 50,000 cells/mm³ (75% of polymorphonuclear leukocytes), Gram staining method that is positive in 30 to 50% of the cases, synovial protein and glucose dosages below the serum levels, increase of lactate and culture that can be positive in 50 to 80% of cases. 21,22 Although many supplementary exams can be used to aid the diagnosis of septic arthritis, many studies demonstrate that none of the tests on their own was conclusive for the diagnosis of this disease, except for the Gram staining method and the positive culturing. 21 The treatment of septic arthritis is based on arthrotomy with direct lavage of the affected joint, followed by early and appropriate antibiotic therapy that is initially performed assuming the most likely etiologic agent, and subsequently modified according to the culture results.…”

“…21,22 Although many supplementary exams can be used to aid the diagnosis of septic arthritis, many studies demonstrate that none of the tests on their own was conclusive for the diagnosis of this disease, except for the Gram staining method and the positive culturing. 21 The treatment of septic arthritis is based on arthrotomy with direct lavage of the affected joint, followed by early and appropriate antibiotic therapy that is initially performed assuming the most likely etiologic agent, and subsequently modified according to the culture results. [22][23][24][25] More recent studies suggest that arthroscopy may be a less invasive alternative for the treatment of this disorder, as it can satisfactorily substitute arthrotomy.…”