Development and initial testing of Asthma Predictive Index for a retrospective study: an exploratory study

Abstract

Objective: Asthma Predictive Index (API) has been used for predicting asthma in prospective or cross-sectional studies, not for a retrospective study. We aim to develop and validate API for a retrospective study. Methods: This is a cross-sectional study based on a convenience sample of children who participated in a previous retrospective cohort study. API was operationalized by two or more wheezing episodes in a year during the first 3 years of life PLUS one of the major or two of the minor criteria of the original API. We assessed validity of retrospective API against Predetermined Asthma Criteria (PAC) which has been extensively used in clinical studies for asthma. We assessed criterion validity by measuring kappa and agreement rate between API and PAC and construct validity by determining associations of API with known risk factors for asthma. Results: Of the eligible 105 children, 55 (52.4%) were male, 90 (85.7%) Caucasians, and the mean age (±SD) was 5.8 years (±1.5). API criteria was met by 15 (14.3%), compared to 33 (31.4%) by PAC, respectively. The agreement rate and kappa between API and definite asthma of PAC were 89.5% and 0.66 (p < 0.01). Atopic conditions, lower parental education, no history of breastfeeding and family history of asthma were significantly associated with risk of asthma by API. Conclusions: Application of API to a retrospective study for ascertaining asthma status is suitable. Our study findings need to be replicated by future studies with a larger sample size.

• Asthma ascertainment
• asthma predictive index
• Predetermined asthma criteria
• retrospective study
• wheezing

Acknowledgements

We are grateful to the staff of the Pediatric Asthma Epidemiology Research Unit for research support. We thank Elizabeth Krusemark for her administrative assistance.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article. This work was supported by a grant from the National Institute of Allergy and Infectious Diseases (R21 AI101277) and Scholarly Clinician Award from Mayo Foundation. Also, this study was made possible using the resources of the Rochester Epidemiology Project, which is supported by the National Institute on Aging of the National Institutes of Health under Award Number R01AG034676. The funding agency was not involved in the design and conduct of the study, in the collection, analysis and interpretation of the data, and in the preparation, review or approval of the manuscript. Y.J.J. had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.