C reactive protein, erythrocyte sedimentation rate, or both, in the diagnosis of atraumatic paediatric limb pain?

Emerg Med J. 2012 Dec;29(12):969-71. doi: 10.1136/emermed-2011-201037. Epub 2012 Feb 14.

Abstract

Objective: To assess if measurement of either C reactive protein (CRP) or erythrocyte sedimentation rate (ESR) individually has an equivalent diagnostic value to measurement of both in identifying orthopaedic infection as the cause of paediatric atraumatic limb pain.

Setting: Emergency department of a paediatric teaching hospital.

Study design: Retrospective study of case notes for patients attending the emergency department with a complaint of atraumatic limb pain and in whom both ESR and CRP were measured at the time of presentation. Laboratory results at the time of presentation were recorded along with the final diagnosis. Receiver operating characteristic (ROC) curves were created using the data and the optimum cut-off values for each of ESR and CRP were derived using the point of best trade off between sensitivity and specificity. Likelihood ratios for ESR and CRP individually and in combination were calculated.

Results: 259 patients were included in the study, of whom 17 were considered to have an orthopaedic infection. ROC curves revealed the best results were obtained using cut-off values of CRP >7 and ESR >12. The combination of a CRP >7 and an ESR >12 gave the best positive likelihood ratio at 6.26 (likelihood ratio 5.34 (CRP >7) vs 2.57 (ESR >12)). For ruling out disease, the combination of CRP ≤7 and ESR ≤12 also outperformed either variable individually (negative likelihood ratio 0.09 (CRP ≤7 and ESR ≤12) vs 0.34 (CRP ≤7) vs 0.18 (ESR ≤12)).

Conclusion: Measurement of both CRP and ESR should be considered an important aid in the investigation of atraumatic limb pain.

MeSH terms

  • Biomarkers / blood
  • Blood Sedimentation*
  • C-Reactive Protein / analysis*
  • Child
  • Child, Preschool
  • Emergency Service, Hospital
  • Extremities*
  • Female
  • Humans
  • Infections / blood
  • Infections / diagnosis*
  • Likelihood Functions
  • Male
  • Pain / blood
  • Pain / diagnosis*
  • ROC Curve
  • Retrospective Studies
  • Sensitivity and Specificity

Substances

  • Biomarkers
  • C-Reactive Protein