Algorithm for identifying K kingae infection of the hip appears unreliable

Investigators conducted a retrospective multicenter study to assess how well the standard Kocher predictive algorithm differentiates between children with Kingella kingae infection of the hip and those with transient synovitis. The 25 Israeli and 9 Spanish children, all of whom had culture-proven K kingae arthritis of the hip, ranged in age from 6 to 27 months and generally had presented with just a mildly abnormal clinical picture.

The Kocher algorithm uses 4 clinical factors to establish the probability of septic arthritis in a child with hip pain-temperature >38.5 C, refusal to bear weight, erythrocyte sedimentation rate (ESR) >40, and white blood cell count >12,000. The presence of each factor represents 1 point in the total score. Scores of 1 to 4 are associated with 3%, 40%, 93%, and 99% probability, respectively, of septic arthritis versus toxic synovitis. In this study, 4 predictors were present in only 3 of the 28 children for whom these data were available. One child with known septic arthritis had no predictor; 6 had 1; 13 had 2; and 5 had 3. According to the Kocher algorithm, this means that 20 children (those with no, 1, or 2 predictors) had scores ≤2, indicating that nearly three-quarters of children in this study with proven K kingae infection would have been considered at low (<40%) risk for septic arthritis and instead would be thought to more likely have toxic synovitis.

Investigators concluded that to exclude K kingae septic arthritis, blood cultures and nucleic acid amplification assays should be performed in young children who present with irritation of the hip, even when fever, leukocytosis, or a high Kocher score are absent (Yagupsky P, et al. J Pediatr. 2014;165[5]:985.e1-989.e1).

Ms Freedman is a freelance medical editor and writer in New Jersey. Dr Burke, section editor for Journal Club, is chairman of the Department of Pediatrics at Saint Agnes Hospital, Baltimore, Maryland. The editors have nothing to disclose in regard to affiliations with or financial interests in any organizations that may have an interest in any part of this article.