Measures of care fragmentation: Mathematical insights from population genetics

Abstract

Objective: To identify novel properties of health care fragmentation measures, drawing on insights from mathematically equivalent measures of genetic diversity. Study Design: We describe mathematical relationships between two measures: (a) Breslau's Usual Provider of Care (UPC), the proportion of care with the most frequently visited provider, analogous to the “frequency of the most frequent allele” at a genetic locus; and (b) Bice-Boxerman's Continuity of Care Index (COCI), a measure of care dispersion across multiple providers, analogous to “Nei's estimator of homozygosity” in genetics. Principal Findings: Just as the frequency of the most frequent allele places a tight constraint on homozygosity, the proportion of care with the most frequently visited provider (UPC) places lower and upper bounds on dispersion of care (COCI), and vice versa. This property presents the possibility of a normalized COCI given UPC (NCGU) measure, which reflects a bounded range of care dispersion dependent on the number of visits with the most frequently visited provider. Mathematical aspects of UPC and COCI also suggest thresholds for the minimal number of patient visits to use when studying fragmentation. Conclusions: Applying knowledge from population genetics elucidated relationships between care fragmentation measures and produced novel insights for care fragmentation studies.