Correlation of C-reactive protein to severity of symptoms in acute influenza A infection

BACKGROUND: Currently there is no objective measure to determine disease severity in patients with acute influenza infection. During acute viral infections, C-reactive protein (CRP) has been shown to be elevated. AIM: To study the relationship between the symptoms of acute influenza A infection and correlate them with the level of inflammation as measured by serum CRP levels. SETTINGS AND DESIGN: Prospective study. MATERIALS AND METHODS: We enrolled a convenience sample of adults presenting to an urban academic emergency department (ED), who had positive Enzyme-linked immunosorbent assay detection of the influenza A antigen. The subjects were excluded if they had immunosuppression, liver disease or were currently taking antiviral medication. A previously validated severity of symptom (SOS) score was calculated by asking the participants to record the severity of seven symptoms associated with influenza infection. The subjects had the serum C-reactive protein (CRP) levels tested during their ED visit. STATISTICAL ANALYSIS: A linear regression model was used with CRP as a predictor of the SOS score. Pearson's product-moment coefficient was used to measure the dependence between the two quantities. RESULTS: Thirty-two subjects were enrolled from January through March 2009, and of those, eight patients were excluded from the analysis, leaving 24 study subjects: 58% were women, of ages 18 to 63 years, with a mean age of 31 years (95% CI 25, 37). The mean SOS score was 14.1 ranging from 6 to 21 (95% CI 12.6, 26.4). The mean CRP score was 24.6 ranging from 0 to 64.7 (95% CI 15.8, 33.4). The correlation coefficient between the SOS score and CRP levels was r = 0.65 (P=0.00056). CONCLUSION: The severity of symptoms associated with acute influenza A infection correlateswith the serum CRP levels.