Background: Bronchial hyper-responsiveness assessed by the methacholine challenge test (MCT) may aid in the diagnosis of asthma, while a negative MCT can help in excluding the diagnosis. Laboratory measures that predict the results of MCT are expected to reduce the number of procedures. We evaluated the capacity of serum high-sensitivity C-reactive protein (hs-CRP) to predict positive or negative MCT in school-aged children and compared it to a marker of airway inflammation, fractional exhaled nitric oxide (FeNO), and markers of allergic sensitization, immune globulin E (IgE) and peripheral blood eosinophils.
Patients and methods: Children aged 6-18 years referred for MCT were included in the study. The results of the MCT were compared to hs-CRP levels and FeNO levels, IgE, and peripheral blood eosinophil counts.
Results: Of the 131 children assessed, 63 (48 %) patients had positive MCTs (Group I), and 68 (52 %) had negative MCTs (Group II). The best cut-off values to predict a positive MCT by receiver-operating characteristic curves were: 23 ppb for FeNO, 120 IU/mL for IgE, and 500/mL for eosinophils; no cut-off value was found for hs-CRP. The odds ratio for a positive MCT with the above cut-off points were 2.43 (1.05-5.61) for FeNO, 2.4 (1.01-5.74) for IgE, 3.32 (1.13-9.75) for eosinophils, and NS for hs-CRP. No correlation was found between hs-CRP and FeNO, IgE, or eosinophil levels.
Conclusions: hs-CRP levels were not helpful, while FeNO, IgE, and eosinophils were useful in the prediction of methacholine bronchial hyper-responsiveness in our group of children.
Trial registration: ClinicalTrials.gov NCT01963585.