Osteoporosis-related fracture case definitions for population-based administrative data

TLDR

Administrative data are widely used to study osteoporosis fracture risk, yet their validity for accurately identifying fracture cases is poorly understood. The study sought to compare fracture incidence derived from administrative data with that from clinically validated data and to assess differences among multiple administrative case definitions. Researchers constructed 35 hip, wrist, humerus, and vertebral fracture definitions from Manitoba hospital and physician billing codes, validated them against the Canadian Multicentre Osteoporosis Study, and applied generalized linear models to compare incidence estimates. Incidence estimates differed by fracture site and definition: hip fractures showed sex‑specific under‑ and over‑ascertainment, the length of the fracture‑free period and use of imaging or repair codes affected over‑ascertainment, hospital‑based definitions under‑ascertained vertebral fractures, while wrist, humerus, and vertebral trends were similar; overall, validity depends on site and definition features.

Abstract

Population-based administrative data have been used to study osteoporosis-related fracture risk factors and outcomes, but there has been limited research about the validity of these data for ascertaining fracture cases. The objectives of this study were to: (a) compare fracture incidence estimates from administrative data with estimates from population-based clinically-validated data, and (b) test for differences in incidence estimates from multiple administrative data case definitions. Thirty-five case definitions for incident fractures of the hip, wrist, humerus, and clinical vertebrae were constructed using diagnosis codes in hospital data and diagnosis and service codes in physician billing data from Manitoba, Canada. Clinically-validated fractures were identified from the Canadian Multicentre Osteoporosis Study (CaMos). Generalized linear models were used to test for differences in incidence estimates. For hip fracture, sex-specific differences were observed in the magnitude of under- and over-ascertainment of administrative data case definitions when compared with CaMos data. The length of the fracture-free period to ascertain incident cases had a variable effect on over-ascertainment across fracture sites, as did the use of imaging, fixation, or repair service codes. Case definitions based on hospital data resulted in under-ascertainment of incident clinical vertebral fractures. There were no significant differences in trend estimates for wrist, humerus, and clinical vertebral case definitions. The validity of administrative data for estimating fracture incidence depends on the site and features of the case definition.