The utility of administrative data for surveillance of children with chronic high risk medical conditions (CHRMC) that places them at risk for influenza related complications

Background. Children with chronic high risks medical conditions (CHRMC) are more likely to develop severe influenza-related complications than those without CHRMC. As a result, prevention and control policies continue to target these risk groups. However, identifying these risk groups remains a challenge. Healthcare administrative data (HAD) have the potential to provide population-based data on children with CHRMC. However, there is lack of studies that have examined comprehensively the utility of HAD for this purpose.;Methods. A retrospective cohort design was used. Two birth cohorts of children born in Alberta during fiscal years 1984/85 (n=41171) and 1994/95 (n=39864) were followed from birth to a maximum of eight years. CHRMC visits were identified from physicians' claims by using ICD-9 codes. A child was classified as having CHRMC using either of the two criteria: criterion A: primary care (≥ 1 paediatrician or ≥ 2 family physician visits only) or consultant (≥ 1 paediatrician and ≥ 2 family physician visits) or ≥ 2 emergency room visits or ≥ 1 hospitalization; criterion B: two or more of the components of criterion A. The validity of the case definition was determined by: (a) determining the positive predictive value (PPV) in terms of the proportion of children with CHRMC who made ≥ 1 subsequent visits post-classification (i.e. evidence of continued healthcare use post-classification); (b) examining the consistency of epidemiological patterns of children with CHRMC between the two cohorts, case definitions and previous studies. The correlates of incidence and prevalence were determined through multivariate regression models.;Results. Both case definitions had the highest PPV when children were followed continuously for at least two years post-classification. The maximum PPV of criterion A for identifying children with CHRMC was 88.7%, while that of Criterion B was 94.6%. Although there were differences in the prevalence and incidence rates between the two cohorts, there was consistency in the epidemiological pattern of CHRMC as follows: males had higher CHRMC incidence and prevalence rates than females; First Nations had the highest CHRMC prevalence and incidence rates; children in rural areas had the highest CHRMC prevalence and incidence rates.;Conclusions. HAD can be used to identify children with CHRMC. The consistency of results between the two cohorts coupled with case definitions with high PPV, provide preliminary evidence that the approach used is valid. These findings are relevant to those who need a practical way to identify target groups for influenza vaccination.;Objectives. (a) To develop a population based method for using HAD to identify children with CHRMC and (b) to determine the correlates of CHRMC incidence and prevalence.