Table 4.

Potential role of HbA1c as a screening tool for gestational diabetes mellitus (GDM). The performance of HbA1c≥42 mmol/mol to identify cases of GDM defined by the three criteria was assessed.

	GDM positive by
HbA1c≥42 mmol/mol	1999 WHO	2015 NICE	2013 WHO
Sensitivity	152/673 (22.6%)	173/792 (21.8%)	200/947 (21.1%)
Specificity	6,080/6,257 (97.2%)	5,982/6,138 (97.5%)	5,854/5,983 (97.8%)
Positive predictive value	152/329 (46.2%)	173/329 (52.6%)	200/329 (60.8%)
Negative predictive value	6,080/6,601 (92.1%)	5,982/6/601 (90.6%)	5,854/6,601 (88.7%)

HbA1c = glycated haemoglobin; NICE = National Institute for Health and Care Excellence; WHO = World Health Organization