Serum concentration of C-reactive protein is not a good marker of bronchial hyperresponsiveness

Introduction: Asthmatic inflammation is responsible for vital features of the disease, including bronchial hyperresponsiveness (BHR). At present we do not have precise markers for monitoring asthmatic inflammation. C-reactive protein (CRP), a marker of systemic inflammation, seemed to be a factor which could also reflect the level of asthmatic inflammation expressed by BHR. Therefore the relationship between CRP concentration and BHR was evaluated. Materials and Methods: One hundred and two patients entered the study. A skin prick test with a broad spectrum of common aeroallergens as well as baseline spirometry and a histamine bronchoprovocation test were performed in each subject. Blood samples for high-sensitivity CRP (hsCRP) measurement were taken before the bronchial challenge tests. Results: Serum hsCRP concentrations ranged from 0.20 to 14.5 mg/l (median: 1.2 mg/l, 25-75% quartiles: 0.6-2.4). Positive skin prick tests were found in 26 subjects. Bronchial hyperresponsiveness was confirmed in 42 patients (first subgroup), while 60 subjects did not demonstrate BHR (second subgroup). Among the patients with BHR, asthma was diagnosed in 33 cases and Corrao syndrome in 9. In both subgroups, serum hsCRP concentrations had similar levels (median: 1.4 mg/l, 25-75% quartiles: 0.8-2.4 and median: 0.9 mg/l, 25-75% quartiles: 0.5-2.8, respectively; p=0.297). There was no statistically significant correlation (r= -0.163, p=0.302) between serum hsCRP concentration and the level of BHR expressed as the 20% provocative concentration for histamine. In addition, hsCRP serum concentration, after adjustment for age, atopy, body mass index, and gender, was not a significant predictor of positive histamine bronchoprovocation test results (p=0.22, OR=0.86,95% CI). Conclusions: Serum hsCRP concentration is not a good marker of BHR, which is mainly dependent on asthmatic inflammation and is measured during bronchial challenge with histamine. This finding is important for interpreting and discussing results obtained from epidemiological and population-based studies on relationships between either CRP concentration and BHR or local and systemic inflammation.