Aims: Diabetes screening strategies using glycated haemoglobin (HbA1c) as first-instance diagnostic parameter may cause failure to detect individuals with abnormal glucose regulation and possible signs of microvascular complications despite "rule-out" HbA1c levels. This cross-sectional study examined the diagnostic performance of HbA1c in relation to fasting and two-hour postload plasma glucose (FPG/2 h-PG), and investigated whether individuals with normal HbA1c but abnormal FPG/2 h-PG have a higher prevalence of moderately increased albuminuria as possible sign of early stage kidney damage.
Methods: A total of 2695 individuals (age 40-79 years, 48% men) without prior diagnosis of diabetes and complete measurement of HbA1c, FPG, 2 h-PG and urine albumin-creatinine ratio (UACR) were taken from a large population-based epidemiological study in the City of Leipzig, Germany.
Results: A total of 2439 individuals (90.5%, 95% CI: 89.4-91.6) had normal HbA1c levels, <39 mmol/mol (<5.7%), while 234 (8.7%, 95% CI: 7.7-9.8) had prediabetes, HbA1c ≥39 and <48 mmol/mol (≥5.7 and <6.5%), and 22 (0.8%, 95% CI: 0.5-1.2) had diabetes, HbA1c ≥48 mmol/mol (≥6.5%), according to HbA1c. Among individuals with normal HbA1c, 35.6% (95% CI: 33.7-37.5) had impaired fasting glucose or impaired glucose tolerance and 1.8% (95% CI: 1.4-2.4) had diabetes according to FPG/2 h-PG. Individuals with normal HbA1c but prediabetic or diabetic FPG/2 h-PG had a significantly higher prevalence of moderately increased albuminuria (9.4%, 95% CI: 7.6-11.5 and 13.3%, 95% CI: 5.8-25.4, respectively) than individuals with normal HbA1c and normal FPG/2 h-PG (3.9%, 95% CI: 3.0-5.0).
Conclusions: The prevalence of prediabetes according to FPG/2 h-PG among individuals with normal HbA1c is considerably high, and the prevalence of moderately increased albuminuria in this group is significantly elevated. Risk factors for diabetes such as age, gender and BMI may help to better identify this at-risk group.
Keywords: HbA1c; albuminuria; diabetes; diagnostic performance.