Abstract
Aim
Diagnosing fracture related infections (FRI) based on clinical symptoms alone can be challenging and additional diagnostic tools such as serum inflammatory markers are often utilized. The aims of this study were 1) to determine the individual diagnostic performance of three commonly used serum inflammatory markers: C-Reactive Protein (CRP), Leukocyte Count (LC) and Erythrocyte Sedimentation Rate (ESR), and 2) to determine the diagnostic performance of a combination of these markers and their value additionally to clinical predictors for FRI.
Method
This cohort study included patients who presented with a suspected FRI at two level I academic trauma centers between February 1st 2009 and December 31st 2017. The parameters CRP, LC and ESR, were obtained from hospital records when FRI was suspected. The gold standard for diagnosing or ruling out FRI was defined as: positive microbiology results of surgically obtained tissue samples, or absence of FRI at a clinical follow-up of at least six months. Separate markers were analysed using hospital thresholds, to determine current diagnostic performance, and continuously, to determine maximum possible diagnostic performance. Multivariable logistic regression analyses were performed to obtain the discriminative performance (Area Under the Receiver Operating Characteristic, AUROC) of (1) the combined inflammatory markers, and (2) the value of these markers additional to clinical parameters.
Results
A total of 168 patients met the inclusion criteria and were included for analysis. CRP had a 38% sensitivity, 34% specificity, 42% positive predictive value (PPV) and 78% negative predictive value (NPV). For LC this was 39%, 74%, 46% and 67% and for ESR 62%, 64%, 45% and 76% respectively. The diagnostic accuracy was 52%, 61% and 80% respectively. The AUROC was 0.64 for CRP, 0.60 for LC and 0.58 for ESR. The AUROC of the combined inflammatory markers was 0.63. Serum inflammatory markers combined with clinical parameters resulted in AUROC of 0.66 as opposed to 0.62 for clinical parameters alone.
Conclusions
The added diagnostic value of CRP, LC and ESR for diagnosing FRI is limited. Clinicians should be aware of this finding in the diagnostic work-up of suspected FRI.
