The validity of the claims-based definition of rheumatoid arthritis evaluated in 64 hospitals in Japan

Table 1 Criteria for definition of “possible cases of RA” subject to chart review

Criteria for definition	N of patients
1. Condition code of RA in an outpatient or inpatient claim	133
2. Diagnosis of RA found in administrative records for rehabilitation and surgical operation	24
3. Prescription of any DMARD	67
4. Rheumatoid factor positive or anti-CCP antibody positive	71
5. “RA” + a post-positional particle ^a in free text	89
6. “Ri-u-ma-ti” in katakana letters meaning RA in free text	247

A patient was defined as a “possible case of RA” if the patient satisfied at least 1 of 6 criteria of the definition. A patient was counted twice or more if the patient met two or more criteria and the sum of ‘N or patients’ exceeded 334
RA Rheumatoid arthritis, DMARD Disease-modifying antirheumatic drugs, anti-CCP antibody Anti-cyclic citrullinated peptide antibody
^a Japanese particles (“joshi”) are short words like “wa”, “wo”, or “ga” indicating various grammatical functions

ISSN: 1471-2474