The relevance of some laboratory tests in the diagnosis of cholestasis and the differentiation between intra- and extrahepatic obstruction.

The Lp-X test and the determination of total gammaglutamyltransferase activity (GGT), its isoenzyme activities (GGT-1 and GGT-2) and the bile acids have been performed in sera obtained from 66 patients with and without cholestasis. The sensitivity of the Lp-X test as an indicator for cholestasis appeared to be 89% with a specificity of 94%. With the exception of GGT-2 activity, the mean values of total GGT, GGT-1 isoenzyme and bile acids differed significantly between the cholestasis positive and negative groups. The diagnostic use of total GGT, isoenzymes and bile acids in the differentiation between intrahepatic cholestasis and extrahepatic biliary obstruction has been investigated. The GGT-1 isoenzyme activity appeared to be the only parameter differing significantly between the two forms of cholestasis.

Effects of plasma exchange on serum cholesterol levels in heterozygous familial hypercholesterolemia.

This study describes the cholesterol-lowering effect of plasma exchange (PE) in seven patients with heterozygous familial hypercholesterolemia. All patients followed an identical protocol consisting of one PE per three weeks during 27 weeks. A cholesterol-lowering diet was prescribed in addition. No supporting cholesterol-lowering medication was given. PE leads to a momentary marked decrease in serum concentrations of both total cholesterol (Tot-c) and high density lipoprotein cholesterol (HDL-c). HDL-c concentration returns more rapidly to the plateau value than Tot-c concentration resulting in a transient favourable Tot-c/HDL-c ratio that disappears after 10-14 days. No reducing or increasing effect of PE on HDL-c concentration was observed after 27 weeks of treatment. Nor was any convincing reducing effect on Tot-c concentration observed.

A new procedure for the visualization of multiple forms of gamma-glutamyl transferase (GGT). Results in normals, patients receiving enzyme-inducing drugs and patients having liver parenchymal lesions.

The activity of gamma-glutamyl transferase (GGT, EC 2.3.2.2) in sera of 68 healthy individuals, of 38 patients receiving anti-epileptic drugs, and of 27 patients having liver parenchymal lesions, was visualized after electrophoresis on cellulose-acetate gel using the substrate gamma-L-glutamyl-p-nitroanilide as a new colour reagent. The liberated p-nitroaniline was converted in situ into a lilac-coloured product using the Bratton-Marshall reaction. In most samples two bands were demonstrated, one located between albumin and alpha1-globulin, called GGT 1, the other located in the alpha2-globulin region, GGT 2. In a few samples a third band, GGT 3, with far less activity than the other bands, occurred in the beta-globulin region. When it occurred, an increase in total GGT activity was mainly due to an increase of GGT-1 activity. The possible role of the determination of GGT-1 activity as a monitor of microsomal enzyme induction is discussed.

The insulin infusion test: a safe procedure?

One hundred and thirty insulin infusion tests (dose 0.05 u kg-1h-1) were carried out in 87 patients with peptic ulcer or after a vagotomy. During the test ECG tracings were taken and blood was sampled for blood glucose and serum potassium determination. In 31% of the tests electrocardiographic changes were seen. The cardiovascular effects were supraventricular and ventricular ectopic beats, ST-T changes and U waves. In 2 tests there were potentially dangerous arrhythmias. A significant relationship was seen between ECG abnormalities and the age of the patients. Such a relationship was not present between ECG changes and glucose and potassium values. It is concluded that the insulin infusion test is probably safer than the conventional Hollander test, but constant monitoring is still required.

Calibration of a turbidimetric assay of serum lipase activity.

Serum lipase activity has been measured by the turbidimetric method of Shihabi and Bishop, using an olive oil suspension as substrate (Shihabi, Z.K. and Bishop, C. (1971) Clin. Chem. 17, 1150-1153). For this method we developed a new calibration procedure, which can be carried out with great precision. Moreover, the technique is simple and fast and therefore suitable for routine use in clinical chemical laboratories. The new calibration procedure consists of the continuous titration of fatty acids, liberated by lipase from the sample, under the same reaction conditions as those used in the turbidimetric assay. A close correlation has been found with the results from the method of Shihabi and Bishop, in which method calibration has been carried out by making use of the linear relationship between the olive oil concentration and the absorbance of the suspension. In our method, the numerical results are twice those obtained by the method of Shihabi and Bishop. A possible explanation for this phenomenon is given.

A simple automated method for the fluorometric titration of calcium in biological fluids,.

A new automatic device has been developed for the determination of the calcium content in biological fluids. The method is based on a fluorometric titration technique, in which calcium is titrated with ethyleneglycolbis-(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA). The end-point of the titration is indicated by quenching of the fluorescence of a calcium-calcein complex, in which calcein is the fluorescein-complexone indicator. To obtain proper results we found it necessary to use a 1 molar potassium hydroxide solution as titration medium. The results are printed out directly in concentration units (mmol/l). In order to carry out these determinations, several electronic and mechanical devices, including a sample-changer, titration cabinet with built-in fluorometer, control unit and electron titrator, were developed. Together they form the new calcium automatic device of which several qualitites such as precision, recovery and correlation have been studied. The disturbing influence of bilirubin has been minimized by using an excitation wavelength of 492 nm, at which there is nearly no absorption by bilirubin. At a concentration of bilirubin of as much as 500 micronmol/l, the recovery of calcium is still about 96%.

The difference between the glucose concentrations in plasma and whole blood.

The glucose concentrations in whole blood (WB) and plasma (P), both prediluted with distilled water and saline, and in their protein-free filtrates, were determined with the Hoffman ferricyanide method. In whole blood prediluted with distilled water the glucose concentration appeared to be 13% higher than in whole blood prediluted with saline. In plasma, predilution with distilled water or saline did not result in different glucose values. Plasma glucose is significantly higher than whole blood glucose independent of the method of pretreatment. A direct relationship between the two values exists, which for protein-free filtrates is represented by Glu(P) equals 1.07 Glu(WB) + 0.11. The glucose concentrations in erythrocytes were calculated and also correlated to plasma glucose values. A good correlation was found when protein-free filtrates were used. Apparently, conversion factors from whole blood to plasma glucose may be used only in cases where samples are deproteinized.