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Several reports have been published commending the use of 14C-labelled triglyceride breath tests in the assessment of fat malabsorption. We report further studies using gyceryl [14C]tripalmitate. Corrections for age, weight or metabolic rate failed to improve the test's ability to discriminate between malabsorbers and control subjects. A correction for respiratory quotient improved the linear correlation observed between the breath test results and daily faecal fat excretion. The significance of these findings is discussed and a number of problems identified which, at present, are preventing the introduction of breath tests for fat malabsorption into routine clinical practice.

A general method for the preparation of 125I-labelled bile acid-histamine or 125I-labelled bile acid-tyramine conjugates is presented. The method is simple, quick and produces ligands in good yield (30%). The characteristics of a radioimmunoassay for conjugated chenodeoxycholic acid, based on an 125I-labelled ligand prepared by the method, are also described. The assay produced values for fasting serum concentrations of conjugated chenodeoxycholic acid that agree well with previous data.

A modification of the manual glucose oxidase-gum guaiacum method of Shipton, B., Wood, P.J. and Marks, V. ((1975) Med. Lab. Tech. 32,33), for use with plasma, is described. The method enables rapid measurement of plasma or serum glucose concentration between 1 and 22 mumol/1 using 10 mul of sample and a single colour reagent. Experience of the method in routine use has shown that the coefficient of variation, beteen batch, is 2.1% and the time taken for analysis of 1 sample, standards and a quality of control sample is 12 min (including centrifugation of blood to obtain plasma).

The clearance of an injected dose of sodium glycocholate has been studied in a group of 23 control subjects who had no evidence of liver disease. A significant correlation was found between bile salt clearance and age. No significant difference was found between the bile salt clearance of male and female subjects. Data derived from a simple compartmental model indicated that decreased clearance of bile salt with age was not specifically related to degenerative changes in hepatocellular integrity, hepatic uptake of bile salts or bile flow.

Investigations into the choice of immunogen, ligand, antiserum and assay conditions for the radioimmunoassay of conjugated cholic acid have been performed with a view to producing optimal assay conditions. Cholic acid-BSA was found to be the best immunogen to produce antibodies to conjugated cholic acid and the response was of an IgG type. Incorporating a spacer (hexanoic acid) between hapten and carrier protein resulted in a decrease in antiserum titre. Optimal conditions for the assay were found using [125I]histamine-glycocholic acid as ligand with a dilution of antiserum to produce 60% binding of ligand and a pH of 7.4. Using these assay conditions no serum effects were found; extraction of serum prior to assay was therefore unnecessary. The assay was sensitive enough to detect post-prandial increased in serum bile acid concentrations following a liquid test meal; no increase was observed throughout the same time period in a fasting control.

The Reflomat System for rapid estimation of plasma or blood glucose concentration has been evaluated. The System gave a linear response throughout its analytical range and the recovery of glucose added to glucose-free plasma was 97-105%. Addition of sodium fluoride to plasma produced a 7-15% reduction in the estimated glucose concentration. Plasma glucose concentration estimated with the Reflomat agreed closely with results of a glucose oxidase and a hexokinase based method, and blood glucose concentration measured with the Reflomat agreed well with results of a glucose oxidase method.