Gestational diabetes: a reappraisal of HBA1c as a screening test.
BACKGROUND
Recent technological advances have made HBA1c a more standardized and user-friendly test with wide availability. This study evaluated HBA1c as a screening test for gestational diabetes mellitus (GDM) in a high-risk population.


METHODS
A total of 442 pregnant women were assessed by HBA1c. Two thresholds were used to "rule in or rule out" GDM, which was confirmed by the "gold-standard" 75-g OGTT (World Health Organization criteria).


RESULTS
Eighty-four (19%) women had GDM while 358 (81%) women were normal; there was a complete overlap of the HBA1c histograms of the two populations. The area under receiver operating characteristic curve of HBA1c to detect GDM was 0.54 (95% CI 0.48-0.61). Using a value of <5.5% to rule out GDM; a sensitivity of 82.1% was achieved, with 15 (16.7%) of 90 women below the threshold being false-negatives (NPV = 83.3%). Using a threshold of HBA1c > or = 7.5% to rule-in GDM; the specificity was 95.8% with 15 (71.4%) of 21 patients over the threshold being false-positives (PPV = 28.6%). HBA1c would eliminate the need for an OGTT in 25.1% (111/442) of whom 27% (30/111) women would be misclassified. At any HBA1c threshold with an acceptable sensitivity, the false-positive rate remained high making it necessary for too many healthy women to undergo the confirmatory OGTT.


CONCLUSIONS
Despite all the progress in methodology, HBA1c remains a poor test to screen for GDM.
Agarwal
Mukesh M
MM
Department of Pathology, Faculty of Medicine, UAE University, PO Box 17666, Al Ain, United Arab Emirates. magarwal@uaeu.ac.ae
Dhatt
Gurdeep S
GS
Punnose
John
J
Koster
Gertrude
G
D000293:Adolescent; D000328:Adult; D016640:Diabetes, Gestational / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology / Q000517:prevention & control; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D011237:Predictive Value of Tests; D011247:Pregnancy; D015995:Prevalence; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D014479:United Arab Emirates / Q000453:epidemiology
D006442:Glycated Hemoglobin