Role of the asthma predictive index (API) in assessing the development of asthma among Brazilian children

Methods Sixty one of 76 children who participated in a previous study (Camara et al JACI 2004;113;551-7) aimed at identifying risk factors for acute wheezing in infancy were re-evaluated at the ages of 2-4 and 8-12 years. They had been seen at the Emergency Room (ER) for an episode of wheezing at the age of 6-24 months. At the age of 8-12 years, parents completed a questionnaire on respiratory symptoms; 52 children underwent skin prick testing with a panel of inhalant and food allergens and 48 performed methacholine challenge tests. Children were considered asthmatic at the age of 8-12 years if they presented previous physician-diagnosed asthma, or at least one of the following symptoms in the past 12 months: wheezing, cough or chest tightness with exercise, or dry cough without colds, accompanied by bronchial hyperresponsiveness, defined by a PC20 <4mg/ml methacholine challenge test. A positive API (at least one major criteria: physician-diagnosed eczema or parental asthma; or 2 of 3 minor criteria: physician-diagnosed allergic rhinitis, wheezing without colds or peripheral eosinophilia ≥4%) was established based on information collected when the children were 2-4 years-old. Sensitivity, specificity, predictive values, likelihood ratios and confidence intervals (CI) of the API for the diagnosis of asthma at 8-12 years-old were calculated. Results Among the 48 children evaluated at school age, 20 (41.7%) were diagnosed with asthma; 13 of them (65%) had a positive API at 2-4 years. Of the 28 children who did not develop asthma, only 9 (32.1%) had a positive API. Sensitivity and specificity of the API were 65% (CI=40.8-84.6) and 67.9% (CI=47.7-84.1), respectively. Positive and negative predictive values were 59.1 (CI=38.7-79.7) and 73.1 (IC=53.9-86.3); and positive and negative likelihood ratios were 2.02 (CI=1.5-2.73) and 0.51 (CI=0.37-0.72), respectively.