Serum isoamylases in liver diseases.

Total serum amylase and its pancreatic and salivary isoamylase activities were studied in serum from 30 normal volunteers and 30 patients with liver disease. Isoenzyme analysis was performed by inhibitor assay and electrophoretic techniques. Six out of 30 patients had total serum amylase activities which exceeded the mean +/- 2 SD value for normal volunteers. The prominent type of isoenzyme was the pancreatic, except for patients with alcoholic cirrhosis. There was no evidence of any other type of isoenzyme by the electrophoretic method, nor was there an age-dependent isoamylase distribution.

Ethnic 'hyperamylasaemia': clarification by isoamylase analysis.

Total serum amylase and its pancreatic (P-type) and salivary (S-type) isoamylase activities were measured in 92 individuals without pancreatic or salivary disease. They were divided into three ethnic sub-groups resident in the UK, namely native Britons, Asians and West Indians. The mean total amylase activity was highest in West Indians (383 U/l), intermediate in Asians (317 U/l) and lowest in Britons (179 U/l). Nine of the 28 Asians and 8 of the 16 West Indians had total amylase activities above the upper end of the reference range for Britons. Such a finding, if accompanied by abdominal symptoms, could lead to exhaustive pancreatic investigation in these ethnic groups unless the appropriate reference range is used. Isoenzyme analysis by inhibitor and electrophoretic techniques indicated that the increase in total amylase was due to increase in S-type isoamylase, P-type isoamylase or both. There was a good correlation between results by the two methods. These differences in serum amylase seem to be genetically determined.

Comparative studies of a new commercial kit for the estimation of vitamin B12 in serum.

A commercial kit method (Technia Diagnostics) for the estimation of serum vitamin B12 claiming certain practical advantages was examined. Analytical and clinical performance were compared with a non-commercial radioisotope B12 method, previously compared to other commercial radioisotope B12 methods. The kit's analytical performance in our hands was satisfactory, although the within-batch precision and recovery of added cyanocobalamin were disappointing. Clinical performance was comparable with the non-commercial B12 method. Establishment of suitable reference ranges as a prerequisite to diagnostic use is apparent.

Acetylcholinesterase and butyrylcholinesterase measurement in the pre-natal detection of neural tube defects and other fetal malformations.

Acetylcholinesterase activity in amniotic fluid was measured at 30 degree C by a reaction rate method employing acetyl-beta-methyl thiocholine as substrate and ethopropazine as a selective inhibitor of butyrylcholinesterase. This assay proved more specific than previously reported methods. Activity was greater in five cases of anencephaly (4.8-9.7 U/l) and nine cases of spinal bifida (5.1-8.6 U/l) than in 50 pregnancies with normal outcome (mean activity 2.0 +/- 0.9 (S.D.) U/l). There was no overlap between results from normal and neural-tube-defect groups, and the results showed no significant correlation with gestational age. Butyrylcholinesterase activity in amniotic fluid was measured using butyrylthiocholine as substrate. In accordance with previous reports, levels were elevated in pregnancies affected by neural tube defects. The ratio butyrylcholinesterase/acetylcholinesterase activity showed similar values for anencephalic, spina bifida and normal pregnancies; however, the two cases of exomphalos investigated could be clearly distinguished from all other groups on this basis.

Comparison of liquid and dried sodium citrate as the anticoagulant for Thrombotest and prothrombin time estimations.

Samples which are taken for the Quick one-stage prothrombin time estimation for the control of patients receiving oral anticoagulant treatment are by convention taken into liquid sodium citrate anticoagulant. Dried sodium citrate has been rejected on the grounds that excessive haemolysis causes activation of clotting factors and therefore falsely short clotting times. Tests were performed with both liquid and dried sodium citrate as an anticoagulant for prothrombin time and Thrombotest. No clinically significant difference between the values given by the two anticoagulants was observed.

An evaluation of commercial radioisotope methods for the determination of folate and vitamin B12.

Five commercial kits for the determination of folate and six kits for the determination of vitamin B12 were investigated. Their performance has been compared with microbiological methods for the two vitamins and with a non-commercial radioisotopic method for B12. The results show the importance of the determination of the reference range for an individual laboratory for each method. The precision of the kits varied appreciably, as did their performance using specimens from patients with different haematological disorders. In particular, certain kits failed to detect all patients with pernicious anaemia. The relative accuracy of the kits was assessed. Various factors which should be taken into account in the final selection of a satisfactory kit are discussed.

Evaluation of the Hematrak differential leucocyte counter.

The main objectives of the evaluation were to: (1) assess accuracy and precision of cell recognition, (2) establish 'reference ranges' and compare with existing ranges, (3) assess machine reliability and suitability for normal working patterns. The accuracy and precision of the instrument were found to be acceptable, within the limits imposed by counting 100 cells in a wedge smear. Reference ranges compared well with established ranges with the exception of monocytes and eosinophils. the instrument was initially evaluated over a 12-week period and has been in routine use for 18 months durng which time it has been found to be very reliable. It has fitted in with the laboratory working patterns without causing any changes in work flow.

An optimised radioimmunoassay for maternal serum alpha1-fetoprotein using polyethylene glycol.

A radioimmunoassay for alpha1-fetoprotein in human maternal serum at 15-20 weeks' gestation using polyethylene glycol to separate bound and free antigen is described. A number of variables has been investigated to define optimal conditions for use at this gestation. The method gives results which agree with those from a double-antibody technique. It has good precision in the critical concentration range, and recoveries are satisfactory. The importance of including sufficient serum protein in the analytical system is stressed. There were systematic differences between three standard preparations of alpha1-fetoprotein, but three out of four antisera tested gave very similar results. The implications for screening for neural tube defects in early pregnancy are discussed.

A simplified radioimmunoassay procedure for serum progesterone.

A simple, rapid radioimmunoassay for progesterone in unextracted serum is described. Cortisol is used to inhibit progesterone binding to corticosteroid binding globulin. The method has been optimised for the determination of progesterone in pregnancy sera or in the luteal phase of the menstrual cycle.

Biochemical and haematological changes during the induction of labour at term with oxytocin, prostaglandin E-2 and prostaglandin F-2alpha.

A total of 75 patients had labour induced near term using intravenous oxytocin, prostaglandin E-2 or prostaglandin F-2alpha. Biochemical and haematological investigations were performed to assess hepatic, renal and adrenocortical function and changes in platelet adhesiveness. In doses which were similarly effective in inducing labour, both prostaglandins were without the water-retaining effect of oxytocin. Adrenocortical stimulation was greatest with oxytocin. No difference between these agents was observed for the other measurements made.

A revised scheme for the evaluation of automatic instruments for use in clinical chemistry.

A revised scheme is described for evaluating automatic instruments used in clinical chemistry. Procedures are outlined for the assessment of mechanical and electrical features, and measurement of the accuracy and precision of individual units. Methods are given for the measurement of analytical precision, carryover, cross-contamination, accuracy, and linearity. The safety of equipment and methods of assessing costs are discussed, and the importance of subjective features is noted. The general principles of the evaluation scheme should be applicable to other types of equipment.

Plasmaphoresis and plasma exchange in the treatment of hyperlipaemia and xanthomatous neuropathy in patients with primary biliary cirrhosis.

Two patients with primary biliary cirrhosis who were increasingly incapacitated by xanthomatous neuropathy are described. Treatment with a low fat diet and cholestyramine was unhelpful but repeated plasmaphoresis by simple venesection in one and plasma exchange using an IBM blood cell separator in the other over a period of several months completely relieved the symptoms of the neuropathy, caused skin xanthomata to recede, and lowered plasma lipid levels in both patients. There was no evidence that this procedure was associated with any deleterious effects on the liver. The size of the cholesterol pool in xanthomata in one patient was estimated to be approximately 35 g, and from the plasma cholesterol response to plasmaphoresis at varying frequency it was suggested that the excess of cholesterol synthesis over degradation was less than 0.3 g/day in one patient and less than 0.4 g/day in the other. On the basis of the response in these patients it is suggested that the turnover rates of lipid pools are relatively slow in biliary cirrhosis and that cholesterol accumulation is more likely to be due to a reduced catabolic rate than to an increased synthetic rate of cholesterol. Plasmaphoresis or plasma exchange are useful methods of treatment for the rare patient afflicted by this resistant and distressing complication of biliary cirrhosis.