Caird (CRP added to Kocher)

Factors distinguishing septic arthritis from transient synovitis of the hip in children. A prospective study.

Caird MS, Flynn JM, Leung YL, et al. The Journal of bone and joint surgery. American volume 2006 · PMID 16757758 · doi:10.2106/jbjs.e.00216

Question

Does adding CRP to the Kocher predictors improve discrimination between septic arthritis and transient synovitis of the hip?

Design

Prospective single-centre cohort of children undergoing hip aspiration.

Patients

Children with an irritable hip who had hip aspiration for suspected septic arthritis.

Intervention

Kocher predictors plus CRP >20 mg/L

Comparison

Final diagnosis of septic arthritis vs transient synovitis

Primary outcome

Predictive value of individual and combined predictors

Key result

Fever was the strongest single predictor and raised CRP was an independent predictor; combining CRP with the Kocher criteria increased the probability of septic arthritis as more predictors were present.

Limitations

Single US centre and only children who were aspirated, introducing selection bias; modest sample size.

Impact on practice

Supports routine CRP measurement in the irritable hip; a normal CRP with no fever makes septic arthritis less likely but does not exclude it.