Diagnosis of diabetes mellitus using HbA1c in Asians: relationship between HbA1c and retinopathy in a multiethnic Asian population.
BACKGROUND
Hemoglobin A1c (HbA1c) ≥ 6.5% (47.5 mmol/mol) has recently been included as a criterion for the diagnosis of diabetes mellitus. It is unclear whether this criterion is appropriate in Asians.


OBJECTIVE
To examine the relationship between HbA1c and diabetes-specific moderate retinopathy in Asian ethnic groups.


METHODS
Four independent population-based cross-sectional studies (2004-2011) in Singapore representing the three major Asian ethnic groups (n = 13 170 adults aged ≥ 25 y: Chinese, 5834; Malays, 3596; and Indians, 3740).


RESULTS
Moderate retinopathy was assessed from digital retinal photographs and defined as a level >43 using the Early Treatment Diabetic Retinopathy Study (ETDRS) scale. Sensitivity, specificity, positive and negative predictive values, and the area under the receiver operating characteristic curve for detecting moderate retinopathy were compared across ethnic groups at different HbA1c cut-points.


RESULTS
HbA1c levels were higher in Indians and Malays compared to Chinese (P < .001). The prevalence of moderate retinopathy below HbA1c <6.5% was <1% in all ethnic groups. At HbA1c ≥ 6.5%, the sensitivity for detecting moderate retinopathy was lower in Chinese subjects compared to Indians and Malays (75.8 vs 86.0 and 85.3%), but specificity (89.7 vs 71.9 and 76.3%) was higher; however, positive predictive value and negative predictive value were similar among Chinese, Indians, and Malays (10.5, 12.3, 12.4%; and 99.6, 99.1, 99.2%, respectively). The AUCs were similar across all three ethnic groups (0.861, 0.851, and 0.853).


CONCLUSIONS
Our study supports the use of HbA1c for diagnosing diabetes in Asians. Despite some interethnic variation in the relationship of HbA1c and retinopathy, a cut-point of 6.5% performs reasonably well in the three major Asian ethnic groups.
Singapore Eye Research Institute (C.S., M.K.I., E.L.M., C.Y.C., T.Y.W.), Singapore 169856; Office of Clinical Sciences (C.S., M.K.I., E.L.M., C.Y.C., T.Y.W.), Duke-NUS Graduate Medical School, Singapore 169856; Departments of Ophthalmology (C.S., M.K.I., E.L.M., C.Y.C., T.Y.W.) and Medicine (E.Y.H.K., M.L.S.T., A.-C.T., E.S.T.), Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597; Center for Quantitative Medicine (W.K.L.), Duke-NUS Graduate Medical School, Singapore 169856; Department of Epidemiology and Public Health (A.S., J.L.), Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597; Department of Medicine (S.C.-L., S.T.), Khoo Teck Puat Hospital, Singapore 768828; and Epidemiology and Disease Control Division (D.H., S.M.), Ministry of Health, Singapore 169854.
Charumathi
C
Sabanayagam
Eric Y H
EY
Khoo
Weng Kit
WK
Lye
M Kamran
MK
Ikram
Ecosse L
EL
Lamoureux
Ching Yu
CY
Cheng
Maudrene L S
ML
Tan
Agus
A
Salim
Jeannette
J
Lee
Su-Chi
SC
Lim
Subramaniam
S
Tavintharan
Ah-Chuan
AC
Thai
Derrick
D
Heng
Stefan
S
Ma
E Shyong
ES
Tai
Tien Y
TY
Wong
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D003930:Diabetic Retinopathy / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D005006:Ethnicity; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012680:Sensitivity and Specificity; D012846:Singapore
D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human