Resumo de Transfer To Human Insulin Is A Potential Risk Factor For Severe Hypoglycaemia - Matthias Egger*, George Davey Smith**, Arthur Teuscher*

Prompted by the clinical observation that some patients with insulin treated diabetes mellitus had more difficulties to recognize hypoglycaemia after transfer to human insulin, a case-control study of hospital admissions for severe hypoglycaemia was performed:

Risk of severe hypoglycaemia in insulin treated diabetic patients transferred to human insulin:
A case control study. British Medical Journal 1991; 303:617-621

The period from 1984 to 1987, when many patients were unselectedly transferred to human insulin because porcine insulin became no longer available, was investigated. Compared to animal insulin use, human insulin use was associated with a hypoglycaemia rate ratio of 2.4.

In order to investigate whether the symptom pattern associated with human insulin hypoglycaemia differed from that with porcine insulin, a prospective randomized double-blind crossover trial was subsequently performed:

Influence of human insulin on symptoms and awareness of hypoglycaemia: A randomised double blind crossover trial. British Medical Journal 1991; 303:622-626
With human insulin, patients were more likely to report neuroglycopenic symptoms such as lack of concentration, restlessness, confusion and visual disturbance, but less likely to report autonomic symptoms like hunger, tremor and sweating. Transfer to human insulin may increase the risk of severe hypoglycaemia. This may be due to the symptom pattern experienced in human insulin hypoglycaemia which could impair patients' ability to recognize hypoglycaemia.
The clinical observation that some patients had more difficulties to recognize hypoglycaemia after transfer to human insulin (1,2), and a number of episodes of severe hypoglycaemia which occurred after transfer to human insulin (I) prompted us to investigate whether transfer to human insulin carried an increased risk of severe hypoglycaemia. The prospective randomized clinical trial (RCT) has been advocated to clarify this issue (3). However, as shown in Table 1, the sample size requirements in a RCT are considerable (4,5). For example, in order to detect a 50 % increase in the risk of severe hypoglycaeinia (relative risk 1.5) when assuming that 5 % of patients experience one episode per year, approximately 2,840 patients would have to be followed up for one year. Case-control studies require smaller sample sizes (Table 1), however, they may be subject to selection bias if patients at high risk for hypoglycaemia were more likely to be transferred to human insulin (6).

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