The utility of diagnostic tests in the detection and prediction of glucose intolerance in the early and late postpartum period in women after gestational diabetes: a longitudinal cohort study

Table 3 Detection of glucose intolerance according to diagnostic tests at different postpartum periods (cross-sectional)

Diagnostic test at 4–12 weeks PP	Test characteristics (%)
Diagnostic test at 4–12 weeks PP	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)
At the 4–12 weeks postpartum (n = 967)
Glucose tolerance defined by 75-g oGTT^a
Fasting glucose (mmol/l)	72.6	100	100	94.3
HbA1c (%)	41.1	84.8	37.5	86.6
2 hr glucose (mmol/l)	50.0	100	100	90.1
Fasting glucose and HbA1c	82.4	84.8	54.7	95.6
oGTT and HbA1c	100	84.8	59.5	100

Diagnostic test at 1-year PP	Test characteristics (%)
Diagnostic test at 1-year PP	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)
At 1-year postpartum (n = 324)
Glucose tolerance defined by FPG and HbA1c^b
Fasting glucose (mmol/l)	86.2	100	100	91.4
HbA1c (%)	39.2	100	100	71.1
Fasting glucose and HbA1c	100	100	100	100

Diagnostic test at 3-year PP	Test characteristics (%)
Diagnostic test at 3-year PP	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)
Glucose tolerance defined by FPG and HbA1c^b
At 3-year postpartum (n = 69)
Fasting glucose (mmol/l)	92.6	100	100	95.3
HbA1c (%)	26.9	100	100	68.9
Fasting glucose and HbA1c	100	100	100	100

PPV positive predictive value, NPV negative predictive value, PP postpartum, FPG fasting glucose, HbA1c glycated hemoglobin
^aoGTT (oral glucose tolerance test) was the gold standard of pathological glucose tolerance at 4–12 weeks postpartum. Normal glucose tolerance, defined as FPG < 5.6 mmol/l or 2 hr glucose < 7.8 mmol/l; Pathological defined as FPG ≥ 5.6 mmol/l or 2 hr glucose ≥ 7.8 mmol/l
^bFPG and HbA1c was the gold standard of pathological glucose tolerance at 1-year or 3-year postpartum. Normal glucose tolerance defined as FPG < 5.6 mmol/l or HbA1c < 5.7%; Pathological glucose intolerance defined as FPG ≥ 5.6 mmol/l or HbA1c ≥ 5.7%. Pathological glucose intolerance includes few women with diabetes and this concerns 22 women with diabetes at 4–12 weeks postpartum, 10 women at 1-year and 1 woman at 3-year postpartum. Due to the low number of women who had diabetes, we grouped them into pathological glucose intolerance and therefore did not use the term prediabetes

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