Issues to consider when attempting to achieve the American Diabetes Association clinical quality requirement for haemoglobin A1c

Abstract

Diabetes mellitus is a chronic disease that is monitored by measurement of haemoglobin A1c (A1C) as an index of glycaemic control. The limitations of using A1C, given the consensus clinical practice recommendations made by the American Diabetes Association, need to be better understood by clinicians. These include bias between DCCT-aligned methods, analytical variation and intra-individual variation. As intra-individual variation is the principal factor determining variation in A1C in rolling means of the last four A1C results and to stable patients, clinicians may need to monitor A1C more frequently to achieve precise results. Laboratories need to report current values and the analyse six internal quality control specimens for each analytical run. 'Delta check' criteria ought to be applied and results reported to highlight acute deviations in A1C. Such procedures will aid the attainment of the clinical quality requirements and give appropriate results for audit purposes.

Implications of different DCCT‐aligned HbA1c methods on GMS clinical indicators

“…From the point of view of the GMS contract where these targets are linked to financial rewards, differences between methodologies could lead to losses or gains of income depending on the relative performance of the methods employed. It is important that the limitations of current DCCT‐aligned HbA 1c methods [14], as well as result interpretation [15,16], are understood by health‐care professionals and policymakers as these may have important financial and clinical implications. A limitation of this study is that it covered patients who attended a specialist diabetic clinic—such specialist clinics are not specifically covered by the GMS targets.…”

The number of unexpected HbA1c variants may be a greater problem in routine practice than is generally realized

“…The finding of an HbA 1c within the reference range for a non‐diabetic patient does not necessarily mean that a haemoglobin variant will not affect the HbA 1c peak in a diabetic patient, as the interference may be subtle in the reference range but may increase steadily with an increase in the HbA 1c level [3]. Not only are there issues of intra‐individual and analytical variation [5], but also there are problems with definition of targets because DCCT alignment is problematical as it is not a true reference method [6]. Furthermore, although there have been several publications detailing problems in HbA 1c analysis due to the common genetic variant haemoglobins [7], the impact in routine practice of the less common genetic variants is not clear.…”

The casino of life

“…Thus, the use of a properly calculated moving average would add objectivity to this common process. 5 Accordingly, we can more easily identify those individuals whose risk factors are on average below a given target, despite having some values above the target, in addition to those who are on average above a target, despite having some values below the target. Such a policy would help to target objectively those who need more intensive follow up, and thus direct the limited resources that are available to healthcare professionals.…”

“…Such a policy would help to target objectively those who need more intensive follow up, and thus direct the limited resources that are available to healthcare professionals. 5 It can be argued that the use of a moving average may potentially obscure a significant deterioration in the risk factor if individual values are overlooked. A critical difference can be calculated encompassing the total variation of a risk factor to detect a significant difference by means of a ''delta check'' in the laboratory information system.…”

“…A critical difference can be calculated encompassing the total variation of a risk factor to detect a significant difference by means of a ''delta check'' in the laboratory information system. 5 The use of a moving average would reduce the effect of variability, which in turn would reduce the critical difference, and thus should increase the identification of true changes in the risk factor. Accordingly, a clinician could more confidently state that a change from a moving average of the last four blood pressure readings of 150 mm Hg to the latest individual reading of 160 mm Hg is the result of a true change in the patient's blood pressure control than a change from a previous individual reading of 150 mm Hg to the latest individual reading of 160 mm Hg.…”