Importance of ethnic base standard references for the diagnosis of osteoporosis in Thai women.

Many studies demonstrated the importance of using ethnic-specific normal database in the diagnosis of osteoporosis (OP). Aims of this study were to assess diagnostic agreement, prevalence of OP, and diagnostic misclassification between Caucasian, Japanese, and Thai normal databases. The cross-sectional study of 3181 Thai women who had bone mineral density (BMD) measurement between January 2008 and December 2010 was performed. BMDs at lumbar spine (LS), femoral neck (FN), and total hip (TH) were derived to T-score by using Caucasian, Japanese, and Thai standard references. Kappa statistic was used to assess diagnostic agreement and misclassification. Diagnostic agreements between Caucasian and Thai reference databases were 0.39 for LS and 0.90 for FN. No statistical agreement was found in TH region (0.01, p value=0.264). Applying the Japanese reference, diagnostic agreements were 0.71 for LS, 0.76 for FN, and 0.94 for TH regions. Prevalence of OP in postmenopausal women was 64.1%, 37.7%, and 41.4% using Caucasian, Japanese, and Thai standard references. Percentage of misclassification was varied by menopausal status and reference database from 11.2% to 48.7%. When applying Japanese databases instead of Caucasian normal databases, overall diagnostic misclassification decreased from 35.1% to 16.1%. Choice of reference database has a significant effect on the diagnosis of low bone mass and OP. Japanese reference database has better diagnostic agreement with previously studied Thai reference database in 1999 than Caucasian reference database.