Most professionals working in diabetes care use the HbA1c level to decide whether they should advise their patients to change treatment or not. Ms Erna Lenters-Westra, a researcher working at the clinical chemical laboratory of the Isala Klinieken in Zwolle, has shown that most of the small, easy-to-use instruments for measuring HbA1c blood levels are not sufficiently accurate. If these instruments are used to diagnose diabetes, this may lead to either overestimation or underestimation of the number of people with the disease as well as the degree of dysregulation in these patients. Lenters-Westra will be awarded a PhD (21 September 2011) by the University of Groningen for her research.
HbA1c is an independent parameter of the degree of control over the blood sugar levels of diabetes patients. It is a measure of the patient’s average blood sugar regulation over the past six to eight weeks and a predictor of the risk of long-term diabetes complications, such as those involving the eyes, kidneys, blood vessels and other organs. HbA1c can also be used to monitor the patient and in deciding to adapt the treatment. HbA1c measurement is not to be confused with the blood glucose monitoring carried out by many diabetes patients with a finger prick test. This blood glucose measurement helps them to decide how much insulin they should take at that time. HbA1c is a measure of how successful the resulting daily adjustments of the blood glucose level have been during a longer period.
To reliably measure HbA1c, the instrument used must be accurate and meet the appropriate quality standards. Lenters-Westra has investigated the performance of eight point-of-care instruments. These small, easy-to-use appliances take immediate HbA1c measurements and are being used more and more often, for example by physicians who want to measure the HbA1c level during patient consultations so that they can discuss it with the patient straight away. GPs and diabetes centres are also increasingly using this type of instrument. The accuracy of six of the eight point-of-care instruments was highly unsatisfactory. Lenters-Westra concluded that the analytical problems posed by these instruments must be investigated to ascertain whether they are truly reliable or not. If this is not done, they should no longer be used in direct patient care to diagnose diabetes or to assess the glucose regulation in diabetes patients.
Recently, the American Diabetes Association has proposed to use HbA1c levels to diagnose diabetes. This underlines the importance of this measurement. Lenters-Westra’s research has contributed to the decision made in the United States that point-of-care instruments must not be used for this purpose.
Laboratories in the Netherlands and BelgiumLenters-Westra also investigated the analytical methods used by 220 Dutch and Belgian laboratories. Her research shows that one in five laboratories use a method that may result in an HbA1c estimate that deviates too much from the actual level. In contrast, some laboratories use a very reliable HPLC method. Lenters-Westra therefore concludes that the quality of the analytical methods varies enormously, from poor to very good. It appears that the clinical chemical laboratories have a lot of expertise concerning the quality of the analytical methods used to determine HbA1c levels. They can thus play an important role in improving this aspect of clinical care.
For more information, please contact the UMCG at +31(0)50 361 22 00 or the Communication Office of the Isala Klinieken at +31 (0)38 424 75 68.
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