The clinical usefulness of glucated haemoglobin in diabetes care evaluated by use of a medical technology assessment strategy.

With the introduction of measurements of glycated haemoglobin in a single blood sample as an index of long-term blood glucose control, the clinically usefulness of these measurements was questioned. The aim of this study was to evaluate measurements of glycated haemoglobin as a new test for metabolic regulation in diabetes management by use of a medical technology assessment strategy. Technology assessment in medicine has been defined as "the art and science of evaluating medical practices", but the strategy has to be adjusted to the medical technology in question always including the following three stages: (a) problem definition and identification of medical technology, (b) analysis by testing the technology with consideration to its benefit and harm, its costs, and its social consequences, and (c) synthesis of the accumulated knowledge about the technology. Based on the out-put from the problem definition we found it necessary to investigate some of the identified problems ourselves before implementation of routine measurements of glycated haemoglobin. Several studies were accomplished to validate the laboratory technology in terms of analytical reliability and its clinical usefulness. We wanted to (1) define goals of analytical quality of assays of glycated haemoglobin based on clinical goals, (2) establish a laboratory method for measurements of glycated haemoglobin fulfilling the defined goals, (3) investigate the ability of measurements of glycated haemoglobin to characterize impaired glucose tolerance, (4) evaluate the clinical usefulness of measurements of glycated haemoglobin in the assessment of metabolic regulation in non-insulin-dependent diabetes mellitus (NIDDM), (5) compare physicians' assessment of metabolic control in insulin-dependent diabetes mellitus (IDDM) with measurements of glycated haemoglobin and determine whether knowledge of glycated haemoglobin values would result in improved metabolic control, and (6) evaluate the organizational and economical consequences of introducing regular measurements of glycated haemoglobin. The analysis required a multi-disciplinary approach. Based on our own studies and the available data information we found that measurements of glycated haemoglobin should be regarded the most clinically appropriate test of long-term glycemia and should be introduced into routine management of adult patients with IDDM and NIDDM with the following guidelines concerning methodologies, clinical utility, organizational consequences. The individual laboratory has to establish and secure its own method since at present we are still without an internationally accepted reference method or reference material. The method should measure HbA1c without measuring the labile intermediate pre-HbA1c and provide separate detection of haemoglobin variants. We investigated the analytical goals for the performance characteristics of assays based on biological variation and on the clinical significance of a certain change in concentrations in the individual. Different strategies lead to different analytical goals of CVA between 2-4%. An oral glucose tolerance test is still required to establish the diagnosis of diabetes. Measurements of glycated haemoglobin have been suggested as an alternative but a considerable overlap between the WHO-defined groups of normal and impaired glucose tolerance was observed. In patients with IDDM our studies demonstrated the limitations of traditional clinical judgement and the laboratory procedures in providing an accurate assessment of blood glucose control and that knowledge of HbA1c values allowed the clinician to identify patients in poor glycemic control and lead to improvement in glycemic control. In patients with NIDDM our study showed that measurements of HbA1c provided information that was otherwise not obtainable in the usual clinical setting in primary health care. Measurements of glycated haemoglobin were easily accepted by patients with diabetes. (ABSTRACT TRUNCA