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 5 Prediction of future glucose intolerance according to diagnostic tests at different postpartum periods (longitudinal)

	Test characteristics (%)
Diagnostic test at 4–12 weeks PP	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)
Prediction of glucose intolerance 1-year postpartum (n = 324)
Glucose tolerance defined by FPG and HbA1c^a
Fasting glucose (mmol/l)	22.3	96.4	80.6	64.9
HbA1c (%)	21.5	87.5	53.8	62.2
2 hr glucose (mmol/l)	10.1	96.9	68.4	61.6
Fasting glucose and HbA1c	35.4	85.6	62.2	66.4
oGTT	26.9	93.8	74.5	65.7
oGTT and HbA1c	37.7	83.1	59.8	66.7

	Test characteristics (%)
Diagnostic test at 4–12 weeks PP	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)
Prediction of glucose intolerance at 3-year postpartum (n = 69)
Glucose tolerance defined by FPG and HbA1c^a
Fasting glucose (mmol/l)	22.2	95.2	75.0	65.6
HbA1c (%)	18.5	78.6	35.7	60.0
2 hr glucose (mmol/l)	5.8	95.1	54.0	59.1
Fasting glucose and HbA1c	37.0	76.2	50.0	65.3
oGTT	22.2	92.9	66.7	65.0
oGTT and HbA1c	37.0	73.8	47.6	64.6

	Test characteristics (%)
Diagnostic test at 1-year PP	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)
Prediction of glucose intolerance at 3-year postpartum (n = 69)
Glucose tolerance defined by FPG and HbA1c^a
Fasting glucose (mmol/l)	59.3	80.5	66.7	75.0
HbA1c (%)	29.6	90.5	66.7	66.7
Fasting glucose and HbA1c	77.8	76.2	67.7	84.2

PPV positive predictive value, NPV negative predictive value, PP postpartum, FPG fasting glucose, oGTT oral glucose tolerance test and HbA1c glycated hemoglobin
^aFPG and HbA1c was considered as 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 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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