An assessment of the adequacy of suspension of insulin in pen injectors.

AIMS: To evaluate the completeness of insulin resuspension by users of neutral Hagedorn (NPH) insulin pens and premixed insulin pens and to relate this to how patients mix insulin before injecting. METHODS: Patients (n = 180) administering a medium duration or premixed insulin in cartridges in disposable pens were asked questions about mixing insulin, injection technique and storing insulin. They were also asked to demonstrate how they mixed their insulin and to send in a half-used pen. The cloudy component equates to the complexed insulin, while the clear component is the diluting fluid or soluble insulin, depending on the type of insulin used. The optical density, a simple way of measuring cloudiness, was measured in each cartridge or disposable pen and was compared with the range obtained from a series of unused control pens. The results for 146 pens containing the most commonly used insulin were included. The 21 patients whose residual pen insulins showed optical densities > 5 SD from the mean were re-interviewed and their medical records were examined in detail. Insulin in the pens was also measured by immunoassay to confirm the utility of optical density measurements. RESULTS: Only one patient mixed the insulin as the manufacturers recommended. In 58 out of 146 pens or cartridges (40%) the opacity of the insulin varied significantly from the expected value. CONCLUSIONS: Most patients in Kirkcaldy do not mix insulin adequately. This may result in their giving different incorrect doses of insulin during the use of each pen. More emphasis should be given to teaching patients to mix correctly.

A model for a multicentre approach to the derivation of reference intervals for thyroid hormones and testosterone for laboratories using identical analysers.

Ideally, every laboratory should derive their own reference intervals for all analytes, but this is difficult in practice. A survey, by questionnaire, of UK laboratories using the Chiron Diagnostics ACS:180 (Chiron Diagnostics Limited, Halstead, Essex, UK), for thyroid function tests, showed that 10% of laboratories derived their own reference intervals, 60% quoted values "adapted" from intervals for previous methods, whilst the remaining 40% quoted (often incorrectly) reference intervals supplied by the manufacturer. In addition only 13% of respondent laboratories derived their own reference intervals for testosterone. As a result of this survey, a study was devised to enable the users of the Chiron Diagnostics ACS:180 immunoassay system to develop and use within-method, between-laboratory reference intervals for thyroid hormones and testosterone. Laboratory collaboration provided the recommended minimum number of data points by establishing a reference sample group. This sample group was used for the calculation of appropriate reference intervals for each hormone according to the guidelines published by the IFCC. We propose this approach as a model for laboratories using identical instrumentation to produce, through collaboration, within-method, between laboratory reference intervals.

Sex difference in the relationship of calcium and magnesium excretion to glycaemic control in type 1 diabetes mellitus.

In order to assess the variability and possible causes of calcium and magnesium losses in diabetes mellitus, urinary calcium and magnesium excretion were monitored six monthly over a 3-year period in 108 stable, type 1 diabetic patients who were having assessment of their clinical status and glycaemic control over the same period. In the patients studied the ranges of excretion of both calcium and magnesium were considerably wider than our non-diabetic reference ranges but the within subject variation in excretion was high. However, using mean values obtained over the study period, a direct relationship was observed between the excretion of both calcium and magnesium and HbA1 in female patients (P < 0.01) but not in males who had similar HbA1 values. The urinary excretion of calcium and magnesium did not relate to any of the other clinical or biochemical indices measured, including body mass index, daily insulin dose, retinal status or albumin excretion. It is suggested that, in poorly controlled patients, females may have a greater risk than males of developing the complications associated with chronic calcium and magnesium loss.

One year comparative trial of metformin and glipizide in type 2 diabetes mellitus.

Forty-eight diabetic subjects with diet-failed Type 2 mellitus, aged 40-69 years, were randomised to metformin (24 patients) or glipizide (24 patients) therapy, and followed prospectively for 12 months. Most subjects were obese. Metformin gave better fasting plasma glucose control compared to glipizide at 24 (p < 0.01), 36 (p < 0.05) and 52 weeks (p < 0.05) with a lower HbA1 concentration at 52 weeks (p < 0.05). Metformin treated patients lost weight whereas glipizide treated subjects gained weight. The weight change between the treatment groups reached significance at 4 weeks (p < 0.05) and was highly significant (p < 0.001) at 8, 12, 24, 36 and 52 weeks. There were no significant changes in either fasting plasma lipid or blood lactate levels in either the metformin or glipizide treated groups. Both drugs caused a similar reduction in albumin excretion rates. In conclusion, metformin gave better glycaemic control than glipizide, with weight loss rather than weight gain in obese Type 2 patients.

Effects of improved glycaemic control on calcium and magnesium homeostasis in type II diabetes.

Poorly controlled type II diabetic patients with hypomagnesaemia, hypermagnesuria, and hypercalciuria were allocated to treatment with either metformin or glipizide, to determine the effects on some indices of mineral metabolism. Despite comparable improvement in glycaemic control, assessed by glucose and haemoglobin A1, there were significant differences between the two groups in the handling of magnesium. Patients receiving metformin showed a reduction in magnesium excretion but remained hypomagnesaemic and hypercalciuric. In contrast, patients receiving glipizide exhibited little change in either magnesium or calcium excretion but showed a significant rise in serum magnesium.