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Use of multiple inflammatory marker tests in primary care: using Clinical Practice Research Datalink to evaluate accuracy

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)e462-e469
Number of pages8
JournalBritish Journal of General Practice
Issue number684
Early online date27 Jun 2019
DateSubmitted - 25 Mar 2019
DateAccepted/In press - 11 Apr 2019
DateE-pub ahead of print - 27 Jun 2019
DatePublished (current) - Jul 2019


Background: Research comparing C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and plasma viscosity (PV) in primary care is lacking. Clinicians often test multiple inflammatory markers, leading to concerns about overuse. Aim: To compare the diagnostic accuracies of CRP, ESR and PV; to evaluate whether measuring two inflammatory markers increases accuracy. Design and Setting: Prospective cohort study in UK primary care using Clinical Practice Research Datalink. Method: Participants were 136,961 patients with inflammatory marker testing in 2014; 83,761 (62.2%) had a single inflammatory marker at the index date, and 53,200 (38.8%) had multiple inflammatory markers. We compared diagnostic test performance of inflammatory markers, singly and paired, for relevant disease (infections, autoimmune conditions and cancers). Results For any relevant disease, small differences were seen between the three tests; areas under receiver operator curve (AUC) ranged from 0.659–0.682. CRP had the highest overall AUC, largely because of marginally superior performance in infection (AUC CRP 0.617 versus ESR 0.589, p<0.001). Adding a second test gave limited improvement in the AUC for relevant disease (CRP 0.682 versus CRP+ESR 0.688, p<0.001); this is of debatable clinical significance. The negative predictive value for any single inflammatory marker was 94% (95% CI 93.8–94.2), compared to 94.1% (93.9–94.4) with multiple negative tests. Conclusions: Testing multiple inflammatory markers simultaneously does not increase ability to rule out disease and should generally be avoided. CRP has marginally superior diagnostic accuracy for infections, and is equivalent for autoimmune conditions and cancers; we therefore suggest this should generally be the first line test.

    Research areas

  • blood plasma, blood tests, c-reactive protein, erythrocyte sedimentation rate, primary care

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