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Practice 10-Minute Consultation

A borderline HbA1c result

BMJ 2019; 365 doi: (Published 11 April 2019) Cite this as: BMJ 2019;365:l1361

Re: A borderline HbA1c result

The paper presented by Barry and Finnikin (2019) demonstrates many of the mistakes currently practiced in the area of diabetes and ‘pre-diabetes’ and illustrate the clear ineffectiveness of the current approach.
- Hba1c is not, and cannot, be measured in mmol/l. It is a measure of the amount of glycated Haemoglobin and must either be expressed as a percentage or as mmol/mol.
- The authors write that ‘A blood test in isolation will not diagnose those at greatest risk of developing diabetes’. This is true, Hba1c is certainly not suitable as a screening test as being used in this case, and the extrapolation to such use is in very problematic. Studies demonstrate that the test lacks the necessary sensitivity to be used alone as a screening test. Why is it being recommended for use in a patient without known diabetes? If the diagnosis has been made it can potentially be used to evaluate blood sugar control but no more. Even patients with known Type 2 DM or ‘pre-diabetes’ can achieve normal HbA1c concentrations with appropriate dietary interventions. Even in combination with GTT the sensitivity is not particularly good.

- Prediabetes diagnosis is also not possible without a glucose/ insulin test. Studies as far back as 40 years ago showed that both positive GTT and negative GTT could not accurately diagnose disturbances of glucose metabolism. That this practice continues remains astounding. Arguments are often presented regarding inconvenience and cost but the price of an incorrect diagnosis is very high.

- The authors list PCOS as a risk factor for diabetes. This is reverse logic. Women with diabetes or, more accurately defined, women with insulin resistance, are at higher risk for PCOS. That does not make PCOS a risk factor for diabetes.

- Cholesterol is elevated. Presumably total cholesterol is meant. However, this is of little relevance in a patient without coronary heart disease. Total cholesterol shows no connection to heart disease. This would be a wasted test. Maybe an evaluation of small-particle LDL concentration, LDL/HDL ratio or TG analysis would be more appropriate if a correct evaluation is to be made.

- The authors say that patients should be educated about lifestyle. We would be interested what exactly is meant here. ‘Encourage Lifestyle Change’ is a term without a clear meaning. Low fat? Low carb? Which do the authors believe is beneficial? The NHS Diabetes Prevention Programme appears to be using the Eatwell Guide. They continue to spread the idea that meals should be based on starchy food. So in patients with a disturbance of glucose metabolism we should be feeding them large amounts of glucose? This makes no sense.

- The authors mention repeatedly that they are concerned with ‘over medicalisation’ but that is exactly what they are doing in this case. The correct tests would determine the need for medicalisation or not. The wrong tests, interpreted incorrectly will lead to that what they fear.

- The authors also mention that a risk assessment tool can be used in general practice at a population level. This creates a degree of conflict when also wishing to treat the patient as an individual. As the epidemiologist Geoffrey Rose describes, using preventative measures to treat entire populations leads to a small or negligible benefit for the individual.

Diabetes strategies have demonstrated their ineffectiveness very clearly by the ever increasing prevalence of diabetes and it’s associated complications. The prevalence of diabetes in the UK continues to rise.

1. Assess the patient for their individual risk of diabetes: family history, weight, BMI, concurrent medical problems
2. By the suspicion of diabetes/prediabetes carry out a glucose/Insulin test to determine the severity of insulin resistance
3. If insulin resistance is confirmed measure Hba1c to document current glucose control
4. Dietary intervention: Insulin resistance and Type 2 Diabetes are diseases of carbohydrate metabolism, the patient should be supported to lower their carbohydrate intake significantly. Less than 25% of food intake. This can be easily achieved by omitting pasta, rice, bread and processed food. This calls for investment in education programmes for doctors and patients in order for knowledge to be disseminated.
5. Evaluation of cardiovascular fitness. This remains the single best predictor of life expectancy and all cause mortality. It needn’t be measured in detail with VO2 max testing. How far can they walk. Can they climb stairs? How many flights.

Competing interests: No competing interests

20 April 2019
Ellis R Muggleton
Consultant Anaesthetist
Klinikum rechts der Isar, Munich
Ismaningerstrasse 22