Elevated C-reactive protein increases diagnostic accuracy of algorithm-defined Stroke Associated Pneumonia in afebrile patients

Lalit Kalra, Craig Smith, John Hodsoll, Andy Vail, Saddif Irshad, Dulka Manawadu

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Background and aim: Pyrexia dependent clinical algorithms may under or over diagnose Stroke Associated Pneumonia (SAP). This study investigates whether inclusion of elevated C-reactive protein (CRP) as a criterion improves diagnosis.
Methods: The contribution of CRP ≥30 mg/L as an additional criterion to a Centres for Disease Control and Prevention (CDC) based algorithm incorporating pyrexia with chest signs and leucocytosis and/or chest infiltrates to diagnose SAP was assessed in 1088 acute stroke patients from 37 UK stroke units. The sensitivity, specificity and positive predictive value of different approaches were assessed using adjudicated SAP as the reference standard.

Results: Adding elevated CRP to all algorithm criteria did not increase diagnostic accuracy compared with the algorithm alone against adjudicated SAP (sensitivity 0.74 [95% CI 0.65-0.81] v 0.72 [95% CI 0.64-0.80], specificity 0.97 [95% CI 0.96-0.98] for both; kappa (0·70 [95% C.I. 0.63-0.77] for both). In afebrile patients (n=965), elevated CRP with chest and laboratory findings had sensitivity of 0.84 [95% CI 0.67-0.93], specificity of 0.99 [95% CI 0.98-1.00] and kappa 0·80 [95% C.I. 0.70-0.90]). The modified algorithm of pyrexia or elevated CRP and chest signs with infiltrates or leucocytosis had sensitivity of 0.94 [95% CI 0.87-0.97], specificity of 0.96 [95% CI 0.94-0.97] and kappa of 0.88 [95% C.I. 0.84-0.93]) against adjudicated SAP.

Conclusions: An algorithm consisting of pyrexia or CRP ≥30 mg/L, positive chest signs, leucocytosis and/or chest infiltrates has high accuracy and can be used to standardise SAP diagnosis in clinical or research settings.
Original languageEnglish
JournalInternational Journal of Stroke
Early online date10 Sept 2018
Publication statusPublished - 2018


  • Acute stroke
  • post-stroke pneumonia
  • Diagnostic accuracy
  • C-reactive protein


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