Characteristics of undiagnosed diabetes mellitus in a population undergoing health screening in Japan: target populations for efficient screening.

AIMS: To estimate the prevalence of undiagnosed diabetes mellitus and its relationship with various risk factors in a population undergoing health screening in Japan. METHODS: Oral glucose tolerance tests were carried out in a total sample of 14,674 Japanese subjects undergoing health screening, aged 20-83 years and without known diabetes. The prevalence of glucose tolerance categories (1999 WHO criteria) was adjusted for sample probabilities. The optimal FPG cut-off point for screening diabetes was estimated using ROC curve analysis for the continuous value of FPG corresponding to a 2-h PG of 200 mg/dl. The number needed to screen (NNTS) to identify one person with undiagnosed diabetes with various risk factors was estimated using the following equation: the number of undiagnosed diabetic plus nondiabetic subjects/the number of undiagnosed diabetic subjects. RESULTS: The prevalence of undiagnosed diabetes among men and women was 6.4% (NNTS 15.7) and 3.2% (NNTS 31.7), respectively. The optimal FPG cut-off point for screening diabetes among men and women was 105 and 106 mg/dl, respectively. NNTS was lower in individuals with more risk factors, e.g. aging (> or =50), BMI (> or =25), hypertension (SBP> or =140 mmHg and/or DBP> or =90 mmHg) and dyslipidemia (TC> or =220 and/or HDL-C<40 and/or TG> or =150 mg/dl), resulting in the lowest NNTS in individuals having all four risk factors among men (6.1) and women (6.7), respectively. CONCLUSIONS: In Japan, screening for diabetes may be more efficient among individuals having an FPG of more than 105-106 mg/dl and with more risk factors, especially in men.