Annals of Clinical Biochemistry: International Journal of Laboratory Medicine

Little is known about the factors controlling somatostatin secretion in man, and data are not available on the changes in circulating levels in various human physiological or pathophysiological states. This is mainly a consequence of the technical difficulties involved in measuring somatostatin in plasma. In the presence of plasma, binding of somatostatin tracer to antibody was consistently decreased by about 20%, and this could not be abolished by the addition of EDTA and aprotinin or by the use of specially prepared somatostatin-free plasma. Furthermore, in the presence of plasma, endogenous somatostatin does not dilute in parallel with synthetic cyclic somatostatin standard.

We have, therefore, developed and validated a radioimmunoassay for somatostatin using prior extraction of the peptide onto leached silica glass. Tyrosine-11 somatostatin was iodinated using lactoperoxidase and purified on ODS silica. This method is superior to iodination using chloramine-T with CMC cellulose purification, and gives a highly purified preparation with a shelf-life of at least eight weeks. Using this tracer and a specific antiserum, the limit of sensitivity of the assay was 10 pg/ml, with an intra-assay coefficient of variation of 12% (n = 16) and inter-assay coefficient of variation of 15% (n = 10). Parallelism has been demonstrated between standard synthetic cyclic somatostatin and all extracted plasma samples. The mean recovery of exogenous somatostatin from plasma was 78%.

The fasting level of immunoreactive somatostatin at 0900 hours in 40 normal subjects ranged from 17 to 81 pg/ml. Care is needed, however, when comparing these values with those obtained from other laboratories since standard preparations of somatostatin vary considerably in their immunopotency.

There has been controversy recently about the validity of the data-analysis of the self-displacement technique for estimation of specific radioactivity. This paper investigates the technique theoretically and provides practical corroboration of the results.

A real time data processing system for a group of three clinical chemistry laboratories (one base and two satellite) has been developed as a successor to one used previously. This paper describes both the inadequacies of the previous worksheet-based system and the advantages of the new system, including flexibility, fast response and comprehensiveness, incorporating urgent routine and long delay (that is, endocrine) requests, and the use of a parallel flow work scheme.

In the preceding article the hardware and organisation of a new data processing system were described. This paper deals with the file structure and operation, the use of management information, the economical use of disc-file space and hardware, and the transferability of the system.

Simple and rapid thin-layer chromatographic methods have been used to investigate the catecholamine metabolites present in the urine of sick children. A semi-quantitative method for 4-hydroxy-3-methoxy-mandelic acid (HMMA) has been devised and compared with the quantitative spectrophotometric procedure. The methods have been performed on both normal subjects and children with catecholamine-secreting tumours, without dietary restriction, and have led to a 50% reduction in the number of samples requiring laborious quantitative determination of HMMA excretion.

The use of polyacrylamide gel electrophoresis as a screening procedure for the characterisation of hyperlipoproteinaemia is described. Sixty-one samples were investigated and classified by four different methods: (1) chemical profile derived from visual appearance and estimation of total cholesterol and triglyceride; (2) ‘SML’ profile by nephelometry; (3) electrophoresis on agarose gel; and (4) electrophoresis on polyacrylamide gel. Polyacrylamide gel electrophoresis showed the closest correlation with the chemical profile when compared with the other two methods. Polyacrylamide gel electrophoresis was found to be a rapid, reliable, and satisfactory procedure for plasma lipoprotein phenotyping.

A rapid and simple extraction procedure followed by gas chromatography using a nitrogen detector is described for the analysis of amitriptyline, nortriptyline, imipramine, and desipramine in 100 μl plasma. No derivitisation of the drugs is required. Recoveries ranged from 93·7 to 104·6%. Within-batch precision and day-to-day variation showed coefficients of variation of less than 10% with the exception of desipramine, for which the day-to-day coefficient of variation was 15·2%. The method was developed to measure plasma concentrations in patients who had taken non-fatal and fatal overdoses of the drugs.

Lysozyme was measured using the synthetic substrate 3′,4-dinitrophenyl tetra-N-acetyl-β-chitotetraoside and the LKB Reaction Rate Analyser. This method has been evaluated by comparing levels obtained with serum samples from healthy individuals and patients with either cancer or inflammatory bowel disease with those obtained from the same specimens using a turbidimetric method. In terms of standard egg-white lysozyme, the colorimetric method gave much higher levels for all samples than the turbidimetric method; however, similar group differences were maintained. For individual serum specimens significant correlation between the two methods was found to occur only in the healthy group. Assay precision for the two methods was similar but the turbidimetric method could detect levels of lysozyme activity which were 10 times lower than those detected by the colorimetric method.

Dilution of serum before assay consistently increased the activity of serum creatine kinase both in normal female subjects and in carriers of Duchenne muscular dystrophy.

Eleven unfit bank executives in sedentary employment exercised daily for 10 weeks according to the Canadian Air-Force 5BX Exercise Programme. Over this period no changes were observed in the glucose or insulin responses to a standard breakfast or to intravenous glucose, or in the glucose response to intravenous insulin. There was a significant reduction in high-density-lipoprotein cholesterol, but total plasma triglyceride and cholesterol levels were unaffected by exercise.

Serum thyroxine binding globulin (TBG) values were correlated with other thyroid function test results and with the clinical condition in 680 patients. The estimation of serum TBG was helpful in the evaluation of thyroid status only in those patients who were either acutely ill, were taking the contraceptive pill, or were pregnant. Further, the derived index, thyroxine: TBG ratio, proved to be a better diagnostic index than the thyroxine: tri-iodothyronine uptake ratio and in many cases would have avoided the use of more expensive and time-consuming tests.

Urinary free 11-hydroxycorticosteroid/creatinine ratios (UFC/Cr) were determined in early morning urine samples from 138 obese subjects attending endocrine clinics in the Glasgow area. The majority of patients (128) had UFC/Cr ratios within the normal range for non-obese subjects (5–55 μmol/mol). Of those with elevated UFC/Cr ratios, further investigations of the hypothalamic-pituitary-adrenal axis confirmed a diagnosis of Cushing's syndrome due to bilateral adrenal hyperplasia in six of the cases and adrenal tumours in a further two patients. In the remaining two patients there was evidence of intermittent adrenal hyperactivity with inconsistent responses to insulin-induced hypoglycaemia tests.

Methods for the estimation of plasma paracetamol which depend on acid hydrolysis to p-aminophenol without a prior extraction step also measure inactive metabolites which are present in high concentrations.

The extent of the overestimate obtained with such methods was determined using 24 samples from patients after paracetamol overdosage. There was a positive error of between 40 and 700 % compared with a high-performance liquid chromatographic reference method which measured only unchanged paracetamol.

These non-specific methods should not be used to determine the need for specific therapy in patients with paracetamol poisoning.

The drug paracetamol (N-acetyl-p-aminophenol; acetaminophen) caused a spurious increase in serum uric acid measured by phosphotungstic acid reduction methods. However, the increase was less than 0·12 mmol/l at plasma levels of paracetamol found in overdosage (40 mg/100 ml) and was small at therapeutic concentrations (less than 4 mg/100 ml). It is concluded that few patients with joint pain who have taken paracetamol as an analgesic will have clinically misleading values for serum uric acid.

An automated kinetic assay for the determination of glucose in blood is described. The method employs the enzyme glucose dehydrogenase in the presence of mutarotase, with nicotinamide adenine dinucleotide as hydrogen acceptor. The analytical parameters of the method are determined and the flexibility of the method in relation to sample volume and sensitivity is discussed. Finally, the method is compared with automated glucose oxidase and hexokinase procedures.

A quick and simple method for estimating 25-hydroxyvitamin D is described. It involves dichloromethane extraction followed by competitive protein-binding assay without chromatography. This assay can be performed on 100 μl of serum and enables 50 samples to be estimated in one working day. The simplicity, speed, and sample size of this method make it very suitable for use in a routine clinical biochemistry laboratory. It is particularly useful when calcium disorders secondary to abnormalities in vitamin D intake and metabolism are suspected.

The laboratory assessment of prolactin status was evaluated by detailed study of 921 subjects (587 normal subjects and 334 patients with pathological conditions). The effect on serum prolactin levels of age, sex, circadian rhythm, pulsatility of secretion, stress, drug ingestion, and pregnancy was defined in normal subjects. The normal prolactin responses to stimulation (TRH, metoclopramide) and suppression (L-dopa, bromocriptine) were also determined. Basal prolactin levels were measured in patients with defined pathological conditions including prolactinoma, idiopathic hyperprolactinaemia, acromegaly, Cushing's disease, chronic renal failure, primary hypothyroidism, pituitary ablation, Kallman's syndrome, Nelson's syndrome, growth hormone deficiency, gonadotrophin deficiency, craniopharyngioma, panhypopituitarism, and chronic progressive arthropathy. Based on these data, a strategy for the routine laboratory assessment of prolactin status is outlined.

Serum ferritin, serum iron, total iron binding capacity, and haemoglobin levels were measured in a group of 36 pregnant women before, one week after, and four weeks after a total dose infusion of iron dextran (T.D.I.). The serum ferritin level is considered to provide a reliable index of maternal iron stores one month, but not one week, after TDI.

Cyclic adenosine 3′, 5′ monophosphate (cyclic-AMP) has been estimated in mucosal biopsy samples removed from the descending colon and rectum at endoscopy to investigate the possibility of using this substance for monitoring pre-malignant changes in the large bowel. Four groups of patients have been studied: those with normal large bowel and rectal mucosa; those with non-malignant inflammatory bowel disease; those with an adenomatous polyp in the descending colon or sigmoid colon; and those with a rectal adenocarcinoma. No difference was found in the cyclic-AMP content of ‘normal’ rectal mucosa, ‘normal’ colonic mucosa, ‘diseased’ colonic mucosa, carcinomas, and uninvolved mucosa adjacent to the polyps. Less cyclic-AMP was found in the polyps than in adjacent uninvolved mucosa. Conversely, more cyclic-AMP was found in the carcinomas than in adjacent uninvolved mucosa. It is concluded that although cyclic-AMP may be a very useful parameter for delineating the extent of the disease in individual patients, it is not a suitable biochemical marker for the screening of neoplastic changes in the large bowel in the population as a whole.

The philosophy and achievements of the first two and a half years of a national quality control scheme for serum growth hormone assays are described. Three serum samples were distributed to participating laboratories every two weeks. A computer-produced summary of the quality control results, which contained scattergrams and a statistical analysis, was returned to participants four weeks after despatch. The performance of 11 experienced (SAS) laboratories was found to fulfil the necessary accuracy criteria, and their results provided the ‘reference group mean’, which served as the target value. Gross positive bias exhibited by several laboratories was due to the use of assays with inadequate sensitivity, and this practice was eliminated during the first six months. During the course of the Scheme the average bias fell from 30 to 14%. With assays of adequate sensitivity, bias was almost invariably due to the misuse of standards. Median within-laboratory, between-batch precision (CV) improved from 23 to 15%. The best performers achieved between-batch CV of 7% which was 1·5 × their within-batch CV: the worst had three- to four-fold differences between within- and between-batch CV. Rudimentary quality control of interpretation was found to result in improvements in interpretation per se and also served to reinforce the desire to improve numerical agreement.

A ‘recommended procedure’ based upon supplied first and second antibody, and a communal ‘reference range’ from 280 untreated acromegalics, both proved valuable.

This review describes the development and application of a novel test to determine levels of human immunoreactive trypsin, an enzyme produced solely by the pancreas, in biological fluids. Being organ-specific, the assay of immunoreactive trypsin should be an ideal marker of pancreatic function, and this is supported by the results of a number of clinical and research investigations. Use of this assay in studies of chronic pancreatitis, juvenile-onset diabetes, and cystic fibrosis has yielded much valuable data, and it is expected that further research will lead to an improved understanding of these and other conditions associated with the pancreas in health and disease.

Simple methods for the detection of keratan sulphate in urine have been applied to over 300 urine samples collected from children and adults with bone and cartilage dysplasias with or without mental retardation. Abnormal keratan sulphate excretion, which is a feature of type IV mucopolysaccharidosis (Morquio syndrome), is found in patients with that condition only during childhood. Abnormal excretion is also a feature of Kniest dysplasia and GM1 gangliosidosis and may be present in a number of other bone and cartilage dysplasias of unknown aetiology.

Two simple, high-yield rapid methods with good reproducibility are described, which permit the determination of radioactivity in plasma D-(—)-3-hydroxybutyrate. The compound is converted to acetoacetate, using a modified enzymatic method. In procedure 1, acetoacetate is reacted with 2, 4-dinitrophenylhydrazine; the resulting hydrazone is oxidised by means of a sample oxidiser, and the product ¹⁴CO₂ is collected in scintillation liquid and counted. In procedure 2, a Conway microdiffusion unit is applied. The acetoacetate is decarboxylated to acetone in the presence of o-phenylenediamine, and the acetone is then diffused into semicarbazide solution. This solution, containing the semicarbazone derivative of labelled acetone, is transferred to liquid scintillation and counted. In both procedures the radioactivity is measured simultaneously in a separate sample which was not subjected to the enzymatic conversion of D-(–)-3-hydroxybutyrate. The difference in radioactivity between the two samples is attributed to labelled D-(–)-3-hydroxybutyrate.

The colorimetric method for the determination of methylmalonic acid by coupling with diazotised p-nitroaniline has been re-examined. Extraction of the diazotised product into amyl alcohol and tetra-methyl ammonium hydroxide considerably increases its stability and sensitivity and reduces background absorbance. Preliminary solvent extraction and ion-exchange chromatography are desirable but can be accomplished simply and quickly using very small quantities of urine. In this form, the method is very reliable and gives recoveries of about 95% and a coefficient of variation of about 7%.

Serum creatine kinase and lactate dehydrogenase isoenzymes were studied in 73 patients with alcoholism, including two patients with clinical alcoholic cardiomyopathy and 28 patients with haemodynamic evidence (systolic time interval abnormality) of disordered myocardial function. No isoenzyme abnormalities suggestive of myocardial injury were observed. We conclude that isoenzyme examination is unsuitable for the early detection of myocardial damage from alcohol.

The distributions of within-person variances in the concentrations of 10 commonly assayed serum constituents have been derived from data on 37 healthy male subjects studied at weekly intervals over a period of five months. All 10 distributions appear to be of log-normal form. The relevance of the findings to the interpretation of differences between serial measurements in a given individual is discussed. Examples are given to show how the information on within-person variances for a particular analyte, organised into a simple graph, may be used to test medical opinions on threshold values for serial changes in the concentration of this analyte in a given individual. In this way, biological variability as well as analytical error may be taken into account quantitatively when assessing the significance of a difference between two serial measurements.

Hydroxyproline metabolism was studied in two patients with type II hyperprolinaemia (HP II) using oral loadings of hydroxyproline or hydroxyproline-ornithine. Δ¹-pyrroline-3-hydroxy-5-carboxylic acid (3 OH-PC) and Δ¹-pyrroline-5-carboxylic acid (PC) were identified in the urine. The urinary excretion of both 3-OH-PC and PC increased in HP II patients but not in healthy controls during oral loading of hydroxyproline and hydroxyproline-ornithine.

The plasma level of proline in patients with HP II is very high but the hydroxyproline concentration is normal or only slightly increased. Therefore one can assume that hydroxyproline is converted to pyrrole-2-carboxylic acid, which is excreted in urine as a glycine conjugate.

In this study it was demonstrated that the highly elevated plasma level of proline in one of the patients with HP II decreased greatly after hydroxyproline-ornithine load; this change was followed by a 40-fold rise in urinary excretion of proline.

In the neonatal period, a red cell deficiency of glucose-6-phosphate dehydrogenase (G-6-PD) may result in jaundice, the severity of which will vary between patients. Diagnosis of this inborn error of metabolism presents a problem if there is a large number of young enzyme-rich red cells in circulation, and this paper details the technique used to confirm a red cell deficiency of G-6-PD in a neonate.

Fetal lung maturity is commonly assessed by determining the ratio of lecithin/sphingomyelin in centrifuged amniotic fluid. In a variety of chromatographic systems currently used for the routine determination of the lecithin/sphingomyelin ratio, including the systems recommended in the original procedure, at least one and frequently two additional phospholipids, normally present in amniotic fluid, tend to chromatograph between or overlapping with lecithin and/or sphingomyelin. These phospholipids have been tentatively identified as phosphatidylserine and phosphatidylinositol. The extra phospholipids contribute significantly to the routine lecithin/sphingomyelin ratio with considerable variation between individual cases. Treatment of dried lipid extracts with cold acetone before chromatography, as suggested in the original lecithin/sphingomyelin ratio procedure, does not remove the interfering phospholipids.

Lamellar bodies, produced by secretory cells in the alveolar epithelium, are the major source of surfactant phospholipid. As the fetal lung matures, the membranous content of the lamellar bodies is secreted into the alveolar spaces and passes into the amniotic fluid, from which it can be isolated in a morphologically recognisable form. A method is described for the rapid isolation of a lamellar body fraction from amniotic fluid using a small air-driven clinical ultracentrifuge. The lamellar body phospholipid content of amniotic fluid increases towards the end of gestation, but the time of onset and the rate of this increase show wide individual variation. Preliminary results suggest that the lamellar body phospholipid content of amniotic fluid may be a useful index of fetal lung maturity.

Two methods for the measurement of plasma creatine kinase MB (CK-MB) activity were compared for analytical performance, cost, practicality, and diagnostic correlation with clinical and electrocardiographic findings in patients admitted to the coronary care unit of a district general hospital. The methods were column chromatography and immunoinhibition. Both methods were found acceptable, and the method to be adopted would depend on the staff arrangements and resources available in the laboratory.

An enzyme multiplied immunoassay technique is compared with a gas-liquid chromatographic technique for the measurement in blood serum of the anticonvulsants phenytoin, carbamazepine, phenobarbitone, primidone, and ethosuximide. The correlation between results obtained by each method was excellent, and both systematic and random errors were well within acceptable limits.

This report describes investigations into the use of sodium salicylate as a cortisol-binding-globulin blocking agent and the subsequent development of a radioimmunoassay for cortisol on unextracted plasma. Cortisol antiserum was raised against a cortisol 3–0-(carboxymethyl) oxime-bovine serum albumin conjugate. A ¹²⁵I-labelled cortisol-tyrosine methyl ester conjugate was also prepared for use in the assay. The radioimmunoassay developed involved no pre-treatment or extraction of the samples before analysis and was extremely simple to perform. Comparison with another radioimmunoassay for cortisol and with the Mattingly fluorimetric assay gave good correlation.

We describe a simple, rapid procedure for the estimation of carbamazepine in plasma. Protein is precipitated, and extraction is achieved by the addition of acetonitrile containing the internal standard N-acetyltryptophan ethyl ester. Separation is by reverse-phase high-pressure liquid chromatography with an acetonitrile: water mobile phase, and detection is by UV absorption at 280 nm. Total retention time is less than 7 minutes. Initial results gave within-batch and between-batch coefficients of variation of less than 2 %, and mean recovery of 97 %. The method is free from interference by other common anticonvulsant drugs.

In the last few years, the use of enzyme labels in immunoassays has been investigated. The aim of this review is to evaluate critically the role of such labels in clinical biochemistry. Special attention has been given to the problems involved in preparing enzyme labels and the ways in which such labels can be used in a variety of heterogeneous and homogeneous assay systems.

The main operational and financial aspects of the maintenance service provided by the West of Scotland Health Boards' Department of Clinical Physics and Bio-Engineering (DCPB) to the clinical chemistry laboratories in the region are described. The scheme, in operation since March 1976, covers all breakdown servicing and engineering preventive maintenance for Technicon Auto-Analyzer equipment valued at £1¼ million in terms of direct replacement costs. The engineering team works closely with the laboratory staffs to ensure that the performance of the equipment is maintained to specification. The direct economies for the Health Boards through savings in maintenance contract charges total around £60 000 per year. In addition, considerable sums have been saved by servicing, modifying, and constructing other instruments for the laboratories outwith the immediate remit of Technicon maintenance. Other economic and operational benefits which result from the scheme are commercially disinterested advice on equipment obsolescence and replacement, and redistribution between the laboratories of old but useful equipment to meet specific needs of the service in the region.

A survey of [H⁺], Pco₂, and Po₂ analyses in 360 laboratories was conducted using three commercial control materials: two aqueous gas-equilibrated buffer solutions (General Diagnostics and IL) and one whole blood material (DADE). There was little difference in precision or accuracy between instruments, classified according to manufacturer into four groups, and materials for [H⁺] and Pco₂, or in precision for Po₂. There were, however, differences in accuracy between instrument groups for Po₂ analysis on the aqueous materials, and in some cases the mean values lay outside the range assigned by the material manufacturers. The 35 instruments outside clinical chemistry departments yielded results similar to those of all participants. The relation between inter- and intra-laboratory precision was similar to that for many analytes, suggesting that neither these materials nor the state of these analyses is unsatisfactory. Aqueous materials should, however, be used with caution as accuracy controls for Po₂.

A comparative evaluation of a gas-liquid chromatographic (GLC) assay and a high-performance liquid chromatographic (HPLC) assay for the determination of plasma theophylline levels has been carried out. Both methods are reliable, accurate, and technically simple and appear to be specific for theophylline. The HPLC system is more sensitive (sample volume 25 μl) than the GLC system (sample volume 500 μl) and is therefore suitable for the estimation of theophylline in microsamples. The HPLC system also has better precision (coefficient of variation: within-batch 2·0%, between-batch 3·0%) than the GLC system (coefficient of variation: within-batch 3·5%, between-batch 5·6%). Good correlation (r = 0·964) was found between plasma theophylline levels (n = 75, observed range 4–186 μmol/l) determined by each procedure. The results of this study indicate that, of the two systems investigated, HPLC is the method of choice.

A radioenzymatic method suitable for the assay of histamine in human blood, urine, plasma, and gastric juice is described. It differs from earlier methods by use of a histamine methyltransferase preparation from pig brain, of high activity tritiated S-adenosylmethionine, and of a heat precipitation step to reduce the previously noted interference from plasma constituents. The method is simpler than those requiring solvent extraction and concentration of histamine, gives recoveries in the range 80–120%, and so eliminates the need for internal standardisation. The method is sensitive and precise with coefficients of variation for blood, urine, and plasma of 5%, 6%, and 13% respectively. The mean ± standard deviation for normal human plasma histamine is 5 ± 4 nmol/l, for whole blood 559 ± 193 nmol/l, and for urine 229 ± 128 nmol/24h.

The results from an external quality control scheme for the assay of paracetamol in serum are reported. A preferential method of assay has not become evident, but, as a result of the scheme, some laboratories have changed or modified their techniques or have re-established the limits of detection.

The majority of laboratories were able to estimate paracetamol satisfactorily at those levels which are of clinical importance. The overall group performance has shown little change.

The programme has had considerable impact in so far as it has led to a mutually useful interchange of information and trouble shooting.

The rise in alkaline phosphatase activity has been studied after reconstitution of 16 commercial preparations of lyophilised quality control material. The effects of storage temperature and analytical method on the rise in activity have also been studied, with a view to producing a reconstitution protocol suitable for recommendation to participants in external quality control surveys. Great differences were found in the magnitude of this rise in activity; these differences can be reduced to negligible levels if the material is mixed for 30 minutes at ambient temperature after reconstitution and then stored for not more than 4 hours at 4°C before assay.

Serum antioxidant activity (AOA) was correlated with the serum caeruloplasmin and serum copper concentration and with the total and available serum iron-binding capacity in 313 normal and abnormal subjects. In all groups except in patients with Wilson's disease (hepatolenticular degeneration) there was a highly significant direct correlation between serum AOA and serum caeruloplasmin concentration. A statistically significant direct correlation between serum AOA and the available iron-binding capacity of serum was found only in normal subjects and in children with thalassaemia major and iron overload. There was no correlation between serum AOA and the serum tocopherol concentration in any of the groups studied.

Immunoreactive melatonin has been studied in normal human volunteers, both men and women, at different times of day and different times of the year. At 2400, but not at 0800 or 1200, there are very large inter-individual variations in mean levels, the maximum difference being fivefold. Intra-individual variations are seen at different times of the year at 2400 and 0800, with low values in spring and autumn and high values in summer and winter.

Results are presented on two patients with complete and two with partial thyroxinebinding globulin (TBG) deficiency. All four subjects had lowered serum thyroxine but were clinically euthyroid. While thyroid hormone uptake tests or TBG assay were effective in the recognition of such individuals, indices based on these tests were misleading in assessing their thyroid status. Results within the reference range were obtained with the Immophase Free Thyroxine assay.

Serum activities of creatine kinase (CK) and its isoenzymes were monitored before and 16 to 20 hours after a variety of surgical procedures and cardioversion. Changes in total CK and CK MM activities in the surgical patients were consistent with the extent of trauma; changes in these activities in the cardioversion patients were more variable, ranging from —2 to 1829 U/l, and were unrelated to the applied electrical force. CK MB activity was unchanged after cystoscopy but rose moderately in 60 % of patients after cholecystectomy, in 43 % of patients requiring only implantation of a new pacemaker box, and in 87 % of patients after implantation of an entire pacemaker system. No increase exceeded 6U/l. Fifty per cent of patients requiring cardioversion showed rises; the maximum value was 40·9 U/l.

Serum succinyltrialanine p-nitroanilide hydrolysing activity was elevated in patients with hepatobiliary diseases. The highest activities were seen in acute cholangitis and intrahepatic cholestasis. The change in succinyltrialanine p-nitroanilide hydrolysing activity was closely associated with those in γ-glutamyltranspeptidase and alkaline phosphatase activities. In some cases, however, the former was more sensitive than the latter.

A radioimmunoassay for testosterone in male plasma utilising a gamma-emitting radioligand and a solid-phase antiserum is described. The radioligand is testosterone-3-(O-carboxymethyl)-oxime coupled to ¹²⁵I-iodohistamine, and the solid-phase antiserum is prepared by coupling antitestosterone-3-bovine serum albumin to cyanogen bromide activated cellulose. The new procedure retains much of the specificity associated with a published, specific radioimmunoassay using an antiserum raised against testosterone-11α-BSA and a tritium radioligand and incorporating a dextran-coated charcoal separation procedure; values obtained by the two procedures are in excellent agreement (r = 0·98, n = 20).

The combination of an ¹²⁵I-radioligand and a solid-phase separation technique greatly increases sample throughput and has the further advantage of reduced running costs and a greater potential for automation. The method gives satisfactory levels of sensitivity, precision, and accuracy.

Creatine in biological fluids was estimated using a modified Sakaguchi procedure. Interference by arginine was eliminated by thin-layer chromatography.