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Isn’t it better to readdress the basis of UKPDS conclusions under new evidence?
- Arya K Kumarasena (20 February 2009)
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Arya K Kumarasena, Director/Consultant Metropolitan Group, 85 Braybrooke Place, Colombo2, Sri Lanka
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As indicated in the editorial [1], there is a general trend that has been established with new research findings. Is it true that diabetic retinopathy (DR) cannot be controlled by maintaining HbA1c % at lower values? As the new research methodologies are more advanced and powerful due to various new practises that has been introduced to over come past mistakes in the research projects, newly published results should convey the more correct situation. Therefore it is of interest to look back and re visit the UKPDS research findings [2], not to criticise its valuable effort, but to learn more lessons from it. On this respect it is important to note following factors that should have lead to UKPDS wrong conclusions, and will also lead to erroneous conclusions in the future, unless proper precautions are taken. I . Contamination of the test sample could lead to wrong conclusions [3] a. UKPDS sample had significant percentage of LADA patients. According to the research design, LADA patients in the conventional treatment group were provided with blood glucose control instructions, to keep HbA1c % around 15, after reaching this value. As such probability of LADA patients in conventional group showing complications related to retinopathy should be very close to 100%. b. On the other hand LADA patients in the insulin treatment group could have easily maintained there HbA1c % much closer to 6, with added insulin. Therefore chances of them showing DR should be very small. c. Actually it is possible to compute and prove that percence of of LADA patients in the sample have influenced the UKPDS33 conclusions. When the influence of these LADA patients is removed, significance of the intensive control on micro vascular complications, mainly determined by DR will fade away. II. Not having clear understanding on the research design could lead to predictions that could not be obtained according to the design. a. As UKPDS research design was based on diabetes control by keeping HbA1c values around 6 or 15, final result should also predict comparison around the same HbA1c values. Conclusion of controlling HbA1c around 6 is better than around 15, does not mean controlling HbA1c values around 6 is better than controlling it around 7 or 8. III. Results obtain for limited period should not be express as a general relation, valid over much longer time spans. a. Kaplan-Meier presentations of the UKPDS33 very clearly shows that in the first few years two groups had more or less same level of DR complications. Further post study follow of the project confirms that just three years after the study period, HbA1c values of the two groups became indistinguishable. Therefore the conclusion of UKPDS is not applicable not only for shorter durations, but also for longer durations b. Apparently period of validity of the indicated conclusion also has been selected by extending the period of research duration, as there was no positive result shown, until the required period is reached References 1. Systemic management of diabetic retinopathy, Editorial BMJ2009;338;b441 2. UKPDS Group (1998) Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patient with type 2 diabetes. (UKPDS 33) Lancet 352:837- 853 3. To find the actual risk factors for coronary artery disease in non -insulin dependent diabetes mellitus, influence of the LADA patients should be removed. Arya K Kumarasena http://bmj.com/cgi/eletters/316/7134/823#190567, 16 Feb 2008s Competing interests: None declared |
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