| Summary: | Abstract Background The Medicare Current Beneficiary Survey (MCBS) limited‐access data provides the unique opportunity to utilize administrative claims and adjusted survey data to investigate trends in utilization and medical expenditure across time. The adjusted survey data is a synthesized, matched version of the original survey data and claims. Researchers may choose adjusted survey data or original claims for cost evaluations according to their research purpose. However, limited research has examined methodological issues when estimating medical cost using different MCBS data sources. Objective The study objective was to examine the reproducibility of individual‐level medical cost using both MCBS data sources: adjusted survey and claims data. Methods This serial cross‐sectional study design analyzed 2006–2012 MCBS data. The sample included noninstitutionalized older Medicare beneficiaries (≥65 years old), with a cancer diagnosis and annually enrolled in Medicare Parts A, B, and D. The population was stratified by diabetes diagnosis. The primary outcome was annual medical cost. We investigated the discrepancies of medical cost estimated from the adjusted survey and original claims data. The agreement between cost estimates from the two sources in each year was determined using the Wilcoxon signed‐rank test. Results A total of 4918 eligible Medicare beneficiaries were included in this study, and 26% of beneficiaries also had diabetes (N = 1275). Significant disagreements in cost estimates between adjusted survey and claims data were present regardless of disease complexity (with or without diabetes). Significant disagreements in medical cost estimates were present in most years, except in 2010 (p = 0.467) and 2011 (p = 0.098), for beneficiaries with cancer and diabetes (p < 0.001 for all). Significant disagreements in medical cost estimates were present in all years for beneficiaries with cancer without diabetes (p < 0.001 for all). Conclusions Based on discrepant cost estimates across data sources, researchers using MCBS to estimate costs should be cautious when using claims or adjusted survey data alone.
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