Validation of an indirect linkage algorithm to combine registry data with Medicare claims.
Academic Article
Overview
abstract
INTRODUCTION: Linkage of registries to Medicare claims data can help extend follow-up for patients receiving medical devices. This study sought to test and validate an algorithm that does not require patient identifiers to link a national vascular registry and Medicare claims data. METHODS: We used data from the Vascular Quality Initiative (VQI), a registry capturing data from more than 600 centers on several different vascular procedures and Medicare claims from 2003 to 2018. We restricted to patients aged 65 years and older who had fee-for-service entitlement at the time of the procedure for this study. We performed an indirect linkage to combine VQI with Medicare at the patient level using a sequential algorithm based on patient's date of birth, sex, zip code, procedure date, and procedure facility. We compared this against a gold standard of a cohort directly linked using social security numbers (SSNs). We calculated the matching rate and accuracy overall, and before and after October 2015 when the ICD-10 system was adopted in the US. RESULTS: A total of 144,045 VQI-Medicare linked patients were in the gold standard cohort. Using the indirect linking algorithm, we matched 133,966 of the 144,045 VQI patients to their Medicare claims (matching rate: 93.0%). Among these, 133,104 patients were correctly matched (matching accuracy: 99.4%). The matching rate was higher when the indirect linkage was implemented in ICD-10 coded data than in ICD-9 coded data (94.0% vs. 92.2%). Accuracy of the indirect linkage remained high for all procedure modules post-ICD-10 coding change (overall 99.4%, range 99.0-99.7%). CONCLUSION: In this study, we successfully used indirect identifiers to link the VQI to Medicare claims with more than 90% success and more than 99% accuracy. When direct linkage of registry-claims data using SSNs is not possible because of availability, confidentiality, or both, this method for indirect linkage provides a suitable alternative. The matching rate and accuracy help ensure the accuracy of long-term follow-up and the completeness and representativeness of linked databases for relevant research and quality improvement initiatives.
