[Fasting or post-challenge blood glucose values for detection of glucose intolerance in screening for metabolic syndrome?].

INTRODUCTION: The normal-pathological threshold of fasting blood glucose values was modified by the new WHO diagnostic criteria (1999) and, in addition, impaired fasting glucose (IFG) was introduced as a new clinical entity. Nevertheless, the 2-h post-glucose challenge criteria and the concept of the impaired glucose tolerance (IGT) remained unchanged. There is no unequivocal agreement whether new fasting or unchanged post-challenge blood glucose criteria should be used for classification of glucose intolerance.

AIMS: To assess the clinical-laboratory characteristics of metabolic syndrome a screening procedure was performed in hypertensive or obese subjects registered within primary health care and the reliability of the new fasting blood glucose criteria was analysed.

PATIENTS AND METHODS: For inclusion, subjects of both sexes aged from 20 to 65 years exhibited at least one of the following clinical characteristics: hypertension (ongoing antihypertensive treatment or raised (> or = 140/90 mmHg) actual blood pressure), abnormal (> 30.0 kg/m2) body mass index [BMI] or elevated waist-hip ratio (> 0.85 in women, > 0.90 in men). Subjects with known diabetes were not involved. An oral glucose tolerance test (OGTT) with 75 g glucose was performed in each subject. Subjects with complete clinical and laboratory findings were statistically analysed (n = 944; women/men: 545/399; age: 46.1 +/- 7.3 years; BMI 32.2 +/- 5.4 kg/m2; waist-hip ratio 0.90 +/- 0.09; x +/- SD).

RESULTS: In the total cohort newly diagnosed diabetes mellitus (based on the 120 min post-challenge glucose values) was found in 87 subjects (9.2%), IGT was detected in 136 cases (14.4%) while normal glucose tolerance was documented in 721 subjects (76.4%). Using fasting blood glucose values for classification, diabetes mellitus was detected in 79 subjects (8.4%), IFG was found in 124 cases (13.1%) while 741 subjects (78.5%) had normal glucose tolerance. Impaired glucoregulation (IGT + IFG) was found in 223 subjects (IGT alone 99 cases [44.4%], IFG alone 87 cases [39.0%], IGT and IFG in combination 37 cases [16.6%]). The sensitivity and specificity of fasting blood glucose criteria for detecting diabetes were 63.2% and 97.1%, respectively, while those for detecting glucose intolerance (IFG and diabetes as well as IGT and diabetes) were 52.9% and 88.2%, respectively. Clinical characteristics of subjects with abnormal post-challenge but normal fasting blood glucose values (n = 105) did not differ significantly from those of subjects with normal post-challenge but abnormal fasting blood glucose values (n = 85) (age: 46.7 +/- 6.9 years vs 46.7 +/- 6.1 years; BMI: 33.1 +/- 5.4 kg/m2 vs 32.3 +/- 4.5 kg/m2; waist-hip ratio: 0.91 +/- 0.09 vs 0.92 +/- 0.07; p > 0.05).

CONCLUSION: OGTT and 2-h post-glucose challenge criteria should be used for the diagnosis of different categories of glucose intolerance in screening for metabolic syndrome.