Abstract
BackgroundAn administrative database covering a whole population such as the national database in Japan may be used to estimate the nationwide prevalence of diseases including rheumatoid arthritis (RA) when a well-validated definition of the disease is available. In Japan, the record linkage between the administrative database and medical charts in hospitals is strictly prohibited. A “hospital-based” validation study is one of few possible validation studies where claims kept inside the study hospital are rearranged into the database structure.MethodsWe selected random samples of 19,734 patients from approximately 1.6 million patients who received medical care between February 2018 and January 2019 in one of the 64 hospitals of the Tokushukai Medical Group. We excluded patients whose observation period was less than 365 days and identified 334 patients who met the definition of “possible cases of RA” whose medical charts were then independently evaluated by two rheumatologists. In a sensitivity analysis, we assessed bias due to misclassifying some patients with RA who did not meet the definition of “possible cases of RA” as a patient with no RA.ResultsThe kappa coefficient between the two rheumatologists was 0.80. The prevalence of RA in the study population was estimated to be 0.56%. We found that [condition code of RA] and ([any disease-modifying antirheumatic drug] or [oral corticosteroid with no systemic autoimmune diseases (other than RA) and no polymyalgia rheumatica]) had a relatively high sensitivity (approximately 73%) and a high positive predictive value (approximately 80%). In a sensitivity analysis, we found that when some patients with RA who did not meet the definition of “possible cases of RA” were misclassified as a patient with no RA, then this would lead to underestimation of the prevalence of the definition-positive patients and the adjusted prevalence.ConclusionsWe recommend using the claims-based definition of RA (found in the current validation study) to estimate the prevalence of RA in Japan. We also suggest estimating the adjusted prevalence using the quantitative bias analysis method, since the prevalence of the disease in the “hospital-based” validation study is different from that in the administrative database.Trial registrationThe current study is not a clinical trial and hence not subject to trial registration.
Highlights
An administrative database covering a whole population such as the national database in Japan may be used to estimate the nationwide prevalence of diseases including rheumatoid arthritis (RA) when a wellvalidated definition of the disease is available
As acknowledged by Nakajima et al [8], the seven definitions of RA used in the study have not been validated and “Definition 3” excludes patients with RA treated by an oral corticosteroid only but not by a Disease-modifying antirheumatic drug (DMARD)
We evaluated 32 claims-based definitions specified by combining 3 inclusion criteria and 1 exclusion criterion using the reference standard where patients were classified as having RA or not having RA according to the final decision agreed upon by the two rheumatologists
Summary
An administrative database covering a whole population such as the national database in Japan may be used to estimate the nationwide prevalence of diseases including rheumatoid arthritis (RA) when a wellvalidated definition of the disease is available. Nakajima et al used data between April 2017 and March 2018 from the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB Japan), and reported that the prevalence of patients with RA was between 0.46 and 0.88% when seven different definitions were used [8]. They recommended “Definition 3,” which was “patients ≥16 years old with 1 International Classification of Diseases, 10th revision (ICD-10) code of RA, and prescribed any disease-modifying antirheumatic drugs (DMARDs) for at least 2 out of 12 months”. As acknowledged by Nakajima et al [8], the seven definitions of RA used in the study have not been validated and “Definition 3” excludes patients with RA treated by an oral corticosteroid only but not by a DMARD
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