Family history as a predictor of asthma risk.

Asthma, one of the most important chronic diseases of children, disproportionately affects minority and low-income children. Many environmental risk factors for asthma have been identified, including animal, mite, and other allergens; cigarette smoke; and air pollutants. Genetics also play an important causative role, as indicated by familial aggregation and the identification of candidate genes and chromosomal regions linked to asthma risk. Using a positive family history of asthma to identify children at increased risk could provide a basis for targeted prevention efforts, aimed at reducing exposure to environmental risk factors. To assess the predictive value of family history as an indicator of risk for childhood asthma, we reviewed population-based studies that evaluated family history of asthma and atopic disease in children with asthma. Our search identified 33 studies from all geographic regions of the world for review. The studies varied in definitions of positive family history and asthma phenotype and used study populations with asthma prevalence ranging from 2% to 26%. Nevertheless, family history of asthma in one or more first-degree relatives was consistently identified as a risk factor for asthma. In ten studies, sensitivity and predictive value of a positive family history of asthma could be calculated: sensitivity ranged from 4% to 43%, positive predictive value from 11% to 37%, and negative predictive value from 86% to 97%. Although a positive family history predicts an increased risk of asthma, it identifies a minority of children at risk. Positive family history may have utility in targeting some individual prevention efforts, but the low positive predictive value limits its value as a means to direct environmental remediation efforts.