A1C and Diabetes Diagnosis Among Filipino Americans, Japanese Americans, and Native Hawaiians

OBJECTIVE

To examine the sensitivity and specificity of A1C ≥6.5% to diagnose diabetes among Filipino Americans, Japanese Americans, and Native Hawaiians.

RESEARCH DESIGN AND METHODS

This was a cross-sectional study among middle-aged adults without prior diagnosis of type 2 diabetes who completed a 2-h 75-g oral glucose tolerance test (OGTT) and A1C measures.

RESULTS

The 933 participants had a mean age of 54.2 years, and 73% were women. A total of 425 (45.5%) subjects had impaired fasting glucose or impaired glucose tolerance, 145 (15.5%) had type 2 diabetes (by OGTT), and 83 (8.9%) had A1C ≥6.5%. The sensitivity and specificity of A1C ≥6.5% to define diabetes (by OGTT) was 40.0 and 96.8% and 68.9 and 95.3%, respectively (by fasting plasma glucose only). However, (64.8%) of Filipino and Japanese subjects with diabetes had isolated postchallenge hyperglycemia; AIC ≥6.5% sensitivity and specificity was 19.1 and 92.1%, respectively, to define isolated postchallenge hyperglycemia in the total sample.

CONCLUSIONS

A1C ≥6.5% had low sensitivity and may delay diagnosis of type 2 diabetes without OGTT. This limitation is exacerbated by isolated postchallenge hyperglycemia in Asian Americans.An international expert committee recently recommended the use of A1C values ≥6.5% to diagnose type 2 diabetes, and an A1C between 6.1 and 6.49% was considered pre-diabetic (1). Data from the National Health and Nutrition Examination Survey showed low sensitivity (44%) but high specificity (99%) (2). We recently showed similar sensitivity (44%) but lower specificity (79%) in older Caucasians from the Rancho Bernardo Study (3). Ethnic minorities have significantly higher A1C levels, even after adjusting for factors that affect glycemia (4,5). The utility of A1C cut point of 6.5% has not been evaluated among Pacific Islanders and Asian Americans who have an elevated prevalence of type 2 diabetes compared with Caucasians (6,7). The objectives of this study were to determine the sensitivity and specificity of A1C compared with the 1) fasting plasma glucose (FPG) test and the 2) oral glucose tolerance test (OGTT) to define type 2 diabetes among Filipino Americans, Japanese Americans, and Native Hawaiians.