Intra-Individual Variation: Significant Changes in Parameters of Lipid and Carbohydrate Metabolism in the Individual and Intra-Individual Variation in Different Test Populations

Abstract

Fasting serum triglyceride, cholesterol, HDL cholesterol, HDL_2&3 cholesterol, fasting plasma glucose and insulin and haemoglobin A₁ were measured under standardised conditions in a group of laboratory volunteers. Intra-individual variation was calculated for each parameter from weekly measurements on at least eleven successive occassions, and the minimum change in each parameter that would be significant at the level P < 0·05 was calculated.

A further study compared intra-individual variation in different test populations. Data from the group of laboratory volunteers were taken to represent intra-individual variation under standard test conditions with an informed test population and data from a group of regularly monitored out-patients undergoing drug therapy for hypercholesterolaemia were taken to represent intra-individual variation under standard conditions in a typical test population. A group of inpatients under strict dietary control provided information on variation under extreme standardisation of test conditions. Intra-individual variation was greatest for all parameters in the outpatient population. Extreme standardisation of test condition reduced intra-individual variation beyond that of the laboratory volunteers only in the case of serum triglyceride.