Diurnal variations in serum biochemical and haematological measurements.

Abstract

SUMMARY Twenty five biochemical and haematological measurements were determined on nonfasting blood and serum samples collected between 9 am and 7 pm from a representative group of 7685 British middle-aged men. Most measurements showed significant diurnal variations, but only for bilirubin, phosphate, and triglyceride did time of day account for more than 5% of the between subject variance. Serum bilirubin concentrations showed a pronounced downward trend in the afternoon, the mean value after 6 pm being 30% lower than the mean value in the morning. Mean serum triglyceride and phosphate concentrations increased steadily through the day. Mean concentrations of potassium, haemoglobin, and haematocrit and red cell count were higher in the morning, while urea and creatinine concentrations and white cell count had higher means in the afternoon. Glucose showed a pattern consistent with short term response to meals. The British Regional Heart Study includes 7735 men aged between 40 and 59 years, who had been randomly selected from the age and sex registers of representative general practices in 24 towns in England, Wales, and Scotland. The criteria for selecting the towns, the general practice, and the subjects, as well as the methods of data collection, have been reported elsewhere.6From each practice's age-sex register some 420 men, aged between 40 and 59 years, stratified into five year age groups of equal size, were selected at random. The list of names was reviewed by the doctors in the practice, who were asked to exclude those whom they thought would not be able to participate because of severe mental or physical disability. The remaining subjects were invited to take part in the study in a letter signed by the general practitioner. Seventy eight per cent of those invited attended for examination by a team of three research nurses over a period of two and a half years.

Birth Weight and Lipids in a National Birth Cohort Study

“…Nonfasting triglyceride, but not total cholesterol levels, have been found to vary significantly throughout the day. 48 Nonfasting levels of LDL cholesterol have been found to be lower, and nonfasting levels of triglycerides are higher than fasting levels, 49 but there were no differences in total cholesterol levels or HDL cholesterol. As triglyceride levels vary throughout the day, we have not included them in the analysis.…”

Hypertension, serum insulin, obesity and the metabolic syndrome

“…Diurnal variation in glucose levels was modest and no adjustments were made for diurnal variation. 19 Serum insulin: Serum insulin concentration was determined by a two-site enzyme-linked immunoadsorbant assay (ELISA) using commercially available monoclonal antibodies raised against human insulin (Novo Nordisk A/S: Denmark), which do not cross-react with proinsulin. 20 Analyses were performed in the Department of Medicine, University of Newcastle upon Tyne, UK, on non-fasting samples, which had been stored at −20°C for between 13 to 15 years.…”

White blood cell count and cardiovascular biomarkers of atherosclerosis

“…First, only one WBC measurement was included in the analysis, and whether an acute, brief inflammatory episode or chronic inflammation was responsible for the observed correlation could not be discriminated. We could not fully exclude individuals with relevant inflammation or infection, but although WBC varies from day to day (Pocock et al 1989), a single measurement can nevertheless predict the risk of death and of specific diseases, including cancer and CVD (Hoffman et al 2004 andMadjid et al 2004). Secondly, we did not estimate the data of other acute inflammatory markers such as CRP and fibrinogen.…”