Elevated C-reactive protein increases diagnostic accuracy of algorithm-defined stroke-associated pneumonia in afebrile patients

Background and aim: Pyrexia-dependent clinical algorithms may under or overdiagnose stroke-associated pneumonia. This study investigates whether inclusion of elevated C-reactive protein as a criterion improves diagnosis. Methods: The contribution of C-reactive protein ≥30 mg/l as an additional criterion to a Centers for Disease Control and Prevention-based algorithm incorporating pyrexia with chest signs and leukocytosis and/or chest infiltrates to diagnose stroke-associated pneumonia 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 stroke-associated pneumonia as the reference standard. Results: Adding elevated C-reactive protein to all algorithm criteria did not increase diagnostic accuracy compared with the algorithm alone against adjudicated stroke-associated pneumonia (sensitivity 0.74 (95% CI 0.65–0.81) versus 0.72 (95% CI 0.64–0.80), specificity 0.97 (95% CI 0.96–0.98) for both; kappa 0.70 (95% CI 0.63–0.77) for both). In afebrile patients (n = 965), elevated C-reactive protein 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% CI 0.70–0.90). The modified algorithm of pyrexia or elevated C-reactive protein and chest signs with infiltrates or leukocytosis 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% CI 0.84–0.93) against adjudicated stroke-associated pneumonia. Conclusions: An algorithm consisting of pyrexia or C-reactive protein ≥30 mg/l, positive chest signs, leukocytosis, and/or chest infiltrates has high accuracy and can be used to standardize stroke-associated pneumonia diagnosis in clinical or research settings. Trial Registration: http://www.isrctn.com/ISRCTN37118456.