Novel Uses of Traditional Algorithms for Septic Arthritis

Abstract

Background: Pediatric musculoskeletal infection (MSKI) is a bacterial infection of the bone, joint, and/or muscle that can be difficult to diagnose. The Kocher and Caird algorithms were developed to distinguish septic arthritis (SA) from transient synovitis (TS) in the hip. These algorithms have been applied to all patients presenting with painful, swollen monoarticular joints regardless of suspicion for SA. The aim of this analysis was to assess the test performance of Kocher and Caird to distinguish MSKI among all pediatric patients presenting with monoarticular joint pain. A secondary aim was to validate the original algorithms.

Methods: We conducted a secondary analysis of a prospective cohort study evaluating the test performance of procalcitonin for suspected SA in a pediatric emergency department. Patients aged 0 to 16 years old who presented with a painful or swollen monoarticular joint were considered for enrollment. We compared the test performance of the traditional algorithms in an expanded population of MSKI versus alternate joint pain using sensitivity, specificity, and area under the curve (AUC). As a sensitivity analysis, missing data for predictors like temperature, erythrocyte sedimentation rate, C-reactive protein, and inability to bear weight were multiply imputed using the Stata program, mi impute, for changed equations.

Results: The Caird algorithm had better test performance compared to the Kocher in all populations. Both algorithms were most discriminative in comparing SA to TS in all joints (AUC: 0.84 Caird and 0.75 Kocher). However, the Caird criteria performed almost as well discriminating MSKI from other causes of monoarticular joint pain in all joints (AUC: 0.79; 95% confidence interval: 0.72, 0.85) and nonhip joints (AUC: 0.80; 95% confidence interval: 0.71, 0.88).

Conclusion: Based on the findings of this study, it is clinically reasonable to apply the Caird algorithm to pediatric patients presenting with monoarticular joint pain of medium and large joints such as the knee, ankle, shoulder, elbow, and wrist, in addition to the hip.

Level of evidence: Level III-retrospective study of novel applications of SA algorithms.