Since fasting glucose alone may be insufficient to diagnose IGT and
diabetes properly, we investigated a step-wise screening model using
the fasting glucose concentration (IFG-1 and IFG-2) as a criterion to
additionally perform an OGTT. Both approaches were able to identify
all women with diabetes. Based on the IFG-2 cut-off (≥6.1 mmol/l), a
total of 15 patients would have been selected for OGTT assessment,
resulting in the additional diagnosis of two cases with diabetes and
two with IGT. The overall PPV of an abnormal 2 h concentration of
the IFG-2 cut-off level was 26.7% and the NPV was 96.1%. The
PPV of IFG-2 for diabetes was 13% and the NPV 100%. Based on
the IFG-1 cut off level (≥5.6 mmol/l), 47 women would have been
selected for OGTT. The PPV of this cut-off level was 17.0% and
the NPV 97.7%. For diabetes the PPV of IFG-1 was 4.3%, with a
NPV of 100%.