ASSESSING THE IMPACT OF BLOOD-SAMPLE TYPE ON THE ESTIMATED PREVALENCEOF IMPAIRED GLUCOSE-TOLERANCE AND DIABETES-MELLITUS IN EPIDEMIOLOGIC SURVEYS

In a prospective study of 353 patients who had undergone coronary arte ry bypass graft surgery a 75 g oral glucose tolerance test was perform ed at 3 months and 12 months after surgery. Venous whole blood glucose and venous plasma glucose samples were assayed on a bench-top analyse r. The World Health Organization diagnostic criteria for impaired gluc ose tolerance and diabetes mellitus were applied to venous whole blood glucose and venous plasma glucose measurements. The difference betwee n the plasma and whole blood concentration of glucose was 0.79-0.86 mm ol l(-1) at a plasma glucose of 7.8 mmol l(-1) and 1.22-1.24 mmol l(-1 ) at a plasma glucose of 11.1 mmol l(-1) (compared to 1.1 mmol l(-1) b y World Health Organization criteria at both cut-points). Despite this , in our subject population with a high prevalence of impaired glucose tolerance (20.3 % at 3 months, 15.3 % at 12 months) and diabetes mell itus (10.1 % at 3 months and 12 months), there was no significant diff erence in the proportion classified impaired glucose tolerance or havi ng diabetes mellitus using venous whole blood glucose compared to veno us plasma glucose. We conclude that despite the minor anomaly between WHO diagnostic criteria based on venous whole blood glucose and venous plasma glucose measurements, these criteria are robust and give broad ly comparable population prevalence of diabetes mellitus and impaired glucose tolerance irrespective of blood sample choice.