bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Human Plasma Proteins on Stabilisation of Platelet Anti-Aggregatory Activity of Prostacyclin
Authors: Mikhailidis D P , Mikhailidis A M , Dandona P
Published: February 2014

Following the demonstration that biological activity of prostacyclin is more stable in plasma than in buffer solutions at physiological pH, we investigated the possibility that a plasma protein may be responsible for this effect. The duration of platelet anti-aggregatory activity of prostacyclin in fatty acid-free human albumin solution was significantly longer than in buffer solutions. The duration of this ‘protection’ was proportional to the concentration of albumin; α, β, and γ-globulin preparations had no ‘protective’ effect. The degree of ‘protection’ by albumin solutions was lower than that by plasma despite identical albumin concentrations. This discrepancy may in part be explained by the tendency of plasma to become alkaline on standing, a change that would tend to stabilise prostacyclin. The clinical relevance of our findings is discussed.
Zinc and Copper Determination in Microsamples of Serum by Flow Injection and Atomic Absorption Spectroscopy
Authors: Rocks Bernard F , Sherwood Roy A , Bayford Linda M , Riley Clifford
Published: February 2014

A new approach to the direct determination of copper and zinc in serum and plasma is described. The sample is injected into a continuously pumped stream of water which is fed into the nebuliser of an atomic absorption spectrophotometer. Analytical results are obtained as a series of sharp peaks on a chart recorder. Analytical variables have been investigated, and the proposed method gave results comparable to those obtained using a conventional method based on precipitation of serum proteins with trichloroacetic acid. The proposed method takes less time to perform and was found to give more precise results than the conventional method. In addition, the flow injection analysis method can be performed using microsamples (10–100 μl) and is thus ideally suited for use on children.
Correlations of Serum Lipids and Lipoproteins with Gamma-Glutamyltransferase and Attitude to Alcohol Consumption
Authors: Fex G , Kristenson H , Trell E
Published: February 2014

The correlation of three markers of alcohol consumption: serum concentration of gamma-glutamyltransferase (GT), high density lipoprotein cholesterol (HDL-cholesterol), apolipoprotein AI (Apo AI), and the results of a questionnaire (Mm-MAST) designed to measure the attitude towards alcohol consumption were determined in a population of healthy men aged 48 years. Apo AI (r = 0·27) and GT (r = 0·31) were correlated (p < 0·001) to the questionnaire score to a similar degree while the correlation between HDL-cholesterol and the questionnaire score was (r = 0·18), somewhat less good but statistically significant (p < 0·01). There was no correlation between GT and HDL-cholesterol or Apo AI.
A Standardised Multicentre Procedure for Plasma Gonadotrophin Radioimmunoassay
Authors: Ferguson K M , Hayes Margaret , Jeffcoate S L
Published: February 2014

A radioimmunoassay method for the assay of luteinising hormone (LH) and follicle-stimulating hormone (FSH) in serum/plasma has been designed for use in laboratories of varying expertise in the United Kingdom. The major sources of experimental error leading to poor within-laboratory performance and between-laboratory comparability were identified: quality of tracer, use of calibration standards, and separation procedure. A simple rugged kit was designed which was extensively tested first in our laboratory and then in a small multi-centre field trial before being made available. It is now used routinely by 26 health service and research laboratories. The working range of the assays is 1–50 IU/l (LH) and 0·3–16 IU/l (FSH). The between-batch reproducibility was 5–11 % (CV) over the dose range 4·8–18 IU/l (LH) and 1·6–15 IU/l (FSH).
Preparation and Evaluation of a 7-Parameter Intralaboratory Control Blood of 4-Month Stability
Authors: Lombarts A J P F , Leijnse B
Published: February 2014

Sterile, fresh concentrates of human red blood cells suspended in a specially designed sterile preservation medium have a stability of all six red blood cell parameters of over four months as measured in the Coulter Model S-Plus II. Substitution under sterile conditions of the unstable white blood cells for (commercially available) fixed (human) red blood cells is a well-established method to obtain simulated white blood cell suspensions of long-term stability.
Chenodeoxycholic Acid Administration Monitored by Serum Bile Acid Profiles: A Dose-Response Study
Authors: Whiting Malcolm J , Down Roger H L , Watts James Mck
Published: February 2014

Serum bile acid analysis was used to monitor the bile acid composition of bile in 16 healthy male volunteers before and during the oral administration of different doses of the gallstone-dissolving bile acid, chenodeoxycholic acid. Daily chenodeoxycholic acid ingestion increased the percentage of this bile acid in bile to a new steady-state level after two to three weeks. Doses of 125, 250, 500, and 750 mg/day significantly increased the proportion of chenodeoxycholic acid in bile from 41% to 55, 61, 78, and 79 %, respectively, during the fourth week of ingestion. The results indicate that useful information concerning chenodeoxycholic acid-induced changes in the bile acid composition of bile can be obtained solely by serum bile acid analysis, and bile collection by duodenal intubation can be avoided.
Homogeneous Fluoroimmunoassay Using Lucifer Yellow VS: Determination of Albumin Plasma
Authors: Bailey M Philip , Rocks Bernard F , Riley Clifford
Published: February 2014

Non-separation fluoroimmunoassays are well suited to automation. The potential sensitivity of such assays has not been realised because the most commonly used label (fluorescein) has absorption and emission spectra which coincide with those of blood constituents and because it has a very small Stokes shift. Lucifer yellow VS has a larger Stokes shift than fluorescein and an emission maximum at longer wavelength. We describe an energy transfer fluoroimmunoassay for plasma albumin in which Lucifer yellow VS is used to label albumin and rhodamine B isothiocyanate is used to label anti-albumin antibodies. The assay shows good correlation with a dye-binding method for albumin and has sensitivity and precision which compare favourably with similar assays using a fluorescein label.
The Costing of Tests in a Laboratory for Clinical Chemistry and Haematology
Authors: Leijten Jan F , Van Der Geer Franca , Scholten Marc NM , Goldschmidt Henk MJ
Published: February 2014

The total cost of a haematology and clinical chemistry laboratory, including external and hospital costs, was studied in a district general hospital in The Netherlands. The main conclusion is that the number of samples analysed is the most important cost-setting factor, but that reduction in the number of requests does not result in the proportional diminution of costs.
A Laboratory Trial of Two New Blood-Glucose Reflectance Meters Featuring Automatic External Calibration
Authors: Walford S , Home P D , Alberti K G M M
Published: February 2014

Two new battery-operated digital reflectance meters for blood glucose measurement have been tested for precision and accuracy in a laboratory trial. Reflocheck® (Boehringer Company Ltd) is calibrated from a bar code printed on each test strip, Reflolux® (Boehringer Company Ltd) from a bar code on acetate film provided with each bottle of BM-Test-Glycemie 20–800R strips, which can also be read visually. Three aqueous standards (3·3, 8·3 and 11·7 mmol/1) were assayed 10 times on each of 10 days. Overall coefficients of variation for Reflocheck were 2·8, 1·7 and 2·0% and for Reflolux 3·1, 1·5 and 2·8% respectively. One hundred and four blood samples measured on the machines gave very high correlations with a manual hexokinase assay: for Reflocheck, y = 1·1 x — 0·7, r = 0·99 and for Reflolux, y = 1·07 x + 0·1, r = 0·99. In the range 2·2–10 mmol, errors of 1 mmol or more occurred on seven occasions with Reflocheck and eight with Reflolux ( n = 80) but none of these errors was of therapeutic significance. The performance of both machines was as good or better than previously published data for similar instruments. The ease of calibration and accuracy of both machines are advantageous as is the use of BM-Test-Glycemie 20–800R by Reflolux which enables a check to be made on visual readings.
Determination of Caffeine, Theophylline and Theobromine in Serum and Saliva Using High-Performance Liquid Chromatography
Authors: Scott N R , Chakraborty J , Marks V
Published: February 2014

A method is described for the measurement of theobromine, theophylline and caffeine in serum and saliva by high-performance liquid chromatography (HPLC). A chloroform/isopropanol extract (85:15, v/v) is evaporated to dryness and chromatographed on a 100 times 4·5 mm id Hypersil octadecylsilane column with UV detection at 280 nm. Theobromine, theophylline, caffeine and the internal standard proxyphylline are satisfactorily resolved with an elution system of acetonitrile/tetrahydrofuran/50 mm acetate buffer, pH 4·0, (4:1:95, v/v). No interference is observed from the presence of xanthine metabolites or any of a number of common drugs examined.

A good correlation was observed between the concentrations of caffeine in serum and in saliva suggesting that salivary measurements may be useful for the study of caffeine pharmacokinetics in man. Caffeine levels determined by the HPLC procedure described here agreed well with those obtained by a radioimmunoassay method. The method is also suitable for determining the xanthine content of beverages by direct injection of diluted samples.
HPLC of Morphine with Electrochemical Detection: Analysis in Human Plasma
Authors: Moore R A , Baldwin D , McQuay H J , Bullingham R E S
Published: February 2014

A method is described for the measurement of morphine in human plasma by ion-paired reverse-phase liquid chromatography. It includes a novel solid-phase extraction of morphine from plasma which is simple, rapid and complete. No known morphine metabolites could be shown to interfere with the measurements. Determination of morphine pharmacokinetics in patients undergoing heart surgery with 1 mg/kg intravenous morphine produced plasma morphine clearances which agreed with established estimates.
Experience with a Simple High-Performance Liquid Chromatography Method for the Analysis of Purine and Pyrimidine Nucleosides and Bases in Biological Fluids
Authors: Bennett M J , Carpenter K H
Published: February 2014

Purine and pyrimidine nucleosides and bases were analysed using an isocratic reverse-phase HPLC technique and utilising simple sample preparation. The method has been successfully used to separate a large number of biologically occurring nucleic acid products within a 30-minute period and to identify them by their chromatographic and optical properties. A number of metabolic disorders have been identified, including hypoxanthine-guanine phosphoribosyl transferase and ornithine carbamyl transferase deficiencies. The method has been in routine use for 2 years performing both quantitative and qualitative analysis and has proved to be robust and reliable.
Serum Total Bile Acid Levels in Patients Receiving Rifampicin and Isoniazid
Authors: Berg Jonathan D , Pandov Harry I , Sammons Herbert G
Published: February 2014

Serum bile acid levels in 61 patients receiving daily doses of rifampicin and isoniazid for the treatment of tuberculosis have been investigated. Bile acids were measured using 3α-hydroxysteroid dehydrogenase in a continuous-flow system. Abnormally elevated levels were found in 44 patients (72%) during the period of study up to 80 days after onset of treatment. The results showed a mean of 24·9 μmol/l and a positively skewed distribution. Whilst marginally raised levels of bilirubin were seen in some samples (mean 8·2 μmol/l), these did not reflect the marked changes observed in bile acids. Patients receiving rifampicin and isoniazid may therefore have markedly elevated levels of total serum bile acids, while other tests used to assess liver function can remain normal.
Plasma Catecholamines: Experience with a Single-Isotope Radioenzymatic Assay
Authors: Dalton R Neil
Published: February 2014

The performance of a rapid and sensitive single-isotope radioenzymatic assay for plasma catecholamines, in a routine clinical chemistry laboratory, is reported and discussed. The value of plasma adrenaline and noradrenaline as tumour markers in the diagnosis, tumour localisation, and post-operative follow-up of four patients with phaeochromocytoma is emphasised.
Changes in Serum Ferritin and other ‘Acute Phase’ Proteins following Major Surgery
Authors: Rubin Caroline , Wood P J , Archer T , Rowe D J F
Published: February 2014

We have measured ferritin concentrations in healthy women, and ferritin, C-reactive protein, iron and total iron-binding capacity in patients undergoing hysterectomy or major gastrointestinal surgery.

Pre-operative serum ferritin concentrations in patients awaiting hysterectomy were significantly lower than those for patients awaiting gastrointestinal surgery and also lower than those for healthy women of similar age. Healthy women aged between 51 and 60 years had significantly higher ferritin levels than women aged 35–50 years.

All patients studied showed large increases in serum ferritin and C-reactive protein concentrations after surgery and approximately similar decreases in iron and in total iron-binding capacity.
The Immunochemical Determination of Apolipoprotein A, Total Apolipoprotein A-I and ‘Free’ Apolipoprotein A-I in Serum of Patients on Chronic Haemodialysis
Authors: Gebhardt D O E , Schicht I M , Paul L C
Published: February 2014

We have determined by radial immunodiffusion the apolipoprotein A content of undelipidated serum samples from 30 patients on chronic haemodialysis and 28 controls using an antiserum against high density lipoprotein (anti-apolipoprotein A). We found that the patients had lower concentrations of apolipoprotein A than the controls. When an antiserum against apolipoprotein A-I was used and the samples were delipidated prior to radial immunodiffusion there was, however, no difference in the total amount of apolipoprotein A-I between the two groups. We were able to explain this difference by measuring the amount of ‘free’ apolipoprotein A-I after crossed immunoelectrophoresis of undelipidated samples, using the antiserum against apolipoprotein A-I. We found that the patients had a higher level of ‘free’ apolipoprotein A-I than the control group. Since apolipoprotein A-I inhibits hepatic triglyceride lipase, the increase in triglycerides observed in patients on haemodialysis may be caused by the greater concentration of ‘free’ apolipoprotein A-I in their serum.
Problems Associated with the Measurement of Uric Acid Using Two Enzyme-Mediated Reaction Systems
Authors: James D R , Price C P
Published: February 2014

We describe the problems encountered with the adaptation of two enzymatic assays for uric acid to a centrifugal analyser. A method employing the uricase/catalase/aldehyde dehydrogenase enzyme system sometimes suffered from interference due to light-scattering species in samples and reagents. The second method employing the uricase/peroxidase system gave results that were lower than the comparison method.
Glycosylated Haemoglobin as an Alternative to the Glucose Tolerance Test for the Diagnosis of Diabetes Mellitus
Authors: Lester Eva , Frazer A D , Shepherd Carole A , Woodroffe F J
Published: February 2014

A comparison was made between the results of a standard 75 g oral glucose tolerance test and total haemoglobin A1 in 168 subjects referred by their general practitioners for the diagnosis of diabetes mellitus. The subjects were classified as having normal, impaired or diabetic glucose tolerance using WHO criteria. Of 108 subjects with normal glucose tolerance only three had haemoglobin A1 concentrations over 8%. Of 10 with impaired glucose tolerance two had haemoglobin A1 concentrations over 8%. Of 47 with diabetic responses, eight had haemoglobin A1 concentrations below 9%. There was a significant difference between the haemoglobin A1 concentration when fasting and that 2 hours after the glucose load in the subjects with a diabetic glucose tolerance response, but no significant difference between the two values in the other subjects.
Myoglobin in the Very Early Phase of Acute Myocardial Infarction
Authors: McComb J M , McMaster E A , Jadgey A A
Published: February 2014

In this study of 35 patients with a definite or possible myocardial infarction seen within the first 5 h of the onset of symptoms and who could clearly define the onset of symptoms, the serum myoglobin was raised in 20% of those in whom blood was sampled within 1 h of the acute event. In 11 of the 35 (31%) patients the serum myoglobin was normal in the first blood sample. Of the nine patients seen within the first 2 h of the onset of symptoms who had frequent samples taken, the first raised serum myoglobin was recorded from 45 min to 3 h 15 min after the onset of symptoms. The serum levels started to rise 15–20 min before levels greater than 85 ng/mL were reached. In the absence of further chest pain more than one peak in serum myoglobin was recorded in 58% of the patients with acute myocardial infarction. The serum myoglobin level returned to normal within 24 h of the onset of symptoms in 44% of patients and within 36 h in 67%.
A Continuous Monitoring Spectrophotometric Method for the Measurement of Angiotensin-Converting Enzyme in Human Serum
Authors: Maguire G A , Price C P
Published: February 2014

A continuous monitoring spectrophotometric method for the measurement of angiotensin-converting enzyme in human serum is described. It is based on the hydrolysis of furylacrylylphenylalanylglycylglycine and applied to an IL Multistat III centrifugal analyser. The method offers better precision and freedom from interference than a fluorimetric assay we have previously described.
A Comparison of the Measurement of Sodium and Potassium by Flame Photometry and Ion-Selective Electrode
Authors: Worth H G J
Published: February 2014

Although sodium and potassium have been the most commonly assayed analytes by clinical chemists for many years there have been fewer analytical principles used routinely than for most other analytes. The introduction of the direct-reading ion-selective electrode has led to a re-examination of the basic concepts of the methods involved, and this in turn to a reassessment of the interpretation of the measurement of sodium in certain clinical situations. As a result there is a case for all clinical chemistry laboratories having access to a direct-reading ion-selective electrode for sodium estimation.
Circannual and Within-Individual Variation of Thyroid Function Tests in Normal Subjects
Authors: Harrop J S , Ashwell K , Hopton M R
Published: February 2014

Blood was taken from normal subjects at monthly intervals over a period of one year for subsequent determination of serum thyroid hormone concentrations. Thyroid-stimulating hormone (TSH) responses to TSH-releasing hormone were performed at 3-monthly intervals. This study provided data on within-individual variation and on seasonally-related changes of these thyroid function tests.

The results showed that, within an individual, thyroid hormone concentrations are maintained within narrow limits. For both thyroxine and triiodothyronine the component contribution of within-individual variation to the population-based variation (the latter also termed the ‘reference interval’, or colloquially the ‘normal range’) was small. This high degree of individuality implies that rigorous comparison of thyroid hormone results against a population-based ‘normal range’ can be potentially misleading.

Despite the limited within-individual variation, seasonally-related changes in thryoid hormone concentrations were apparent, with higher thyroxine and triiodothyronine values seen in winter months. A tendency to a greater TSH response to TSH-releasing hormone was also noted at this time. Conceivably these changes could reflect a centrally-mediated response of the hypothalamic—pituitary—thyroid axis to environmental temperature.
Changes of Methodology and Their Potential Effects on Data Banks for Drug Effects on Clinical Laboratory Tests
Authors: Evans G O
Published: February 2014

Some of the implications of method changes on data banks for the effects of drugs on clinical laboratory tests are discussed. Using data from Wellcome Clinical Chemistry Quality Control Programmes, separated by a period of ten years, significant changes of methodology used by participants are illustrated. These changes are related to a recognised listing of drug effects in clinical chemistry tests available in 1975. It is suggested that information from external quality assessment schemes is used periodically to review the relevance of data in relation to major changes of methodology.
Preparation, Extraction and High Performance Liquid Chromatography of Cyclosporin a from Plasma that Contains Interfering Compounds
Authors: Oosthuizen M M J , Jacobs D R , Myburgh J A
Published: February 2014

Cyclosporin A (Cya) in human plasma-containing interfering compounds was determined by high performance liquid chromatography (HPLC) after the plasma had been subjected to incubation with proteinase K. This hydrolytic enzyme did not hydrolyse the cyclosporins and was therefore an ideal aid in eliminating interfering peptides selectively. The use of Extrelut® as an extraction aid contributed much to higher yields of cyclosporins. Ethyl acetate, the extraction solvent used, gave less complex profiles on HPLC chromatograms than other solvents (eg diethyl ether and methanol) and contributed to a shorter chromatographic period per sample, an advantage in repetitive determinations.
An Examination of the Hexokinase Method for Serum Glucose Assay Using External Quality Assessment Data
Authors: Westwood Alan , Bullock David G , Whitehead Thomas P
Published: February 2014

Hexokinase methods for serum glucose assay appeared to give slightly but consistently higher inter-laboratory coefficients of variation than all methods combined in the UK External Quality Assessment Scheme; their performance over a two-year period was therefore compared with that for three groups of glucose oxidase methods. This assessment showed no intrinsic inferiority in the hexokinase method. The greater variation may be due to the more heterogeneous group of instruments, particularly discrete analysers, on which the method is used. The Beckman Glucose Analyzer and Astra group (using a glucose oxidase method) showed the least inter-laboratory variability but also the lowest mean value. No comment is offered on the absolute accuracy of any of the methods.
Determination of Aluminium in Human Tissues by Flameless Atomic Absorption Spectroscopy and Comparison of Reference Values
Authors: Bouman A A , Platenkamp A J , Posma F D
Published: February 2014

Aluminium in human tissues has been determined by flameless atomic absorption spectroscopy (AAS). Tissues were dried at 110°C and digested with concentrated nitric acid at 50°C overnight. After dilution with distilled water the samples were measured. The aluminium levels of the controls (healthy individuals who died as a result of an accident) appeared to be: grey matter 2·1±1·0 (mean±SD), white matter 1·7±0·5, spinal cord 3·3±1·5, kidney 1·9±0·7, heart 2·1±1·1, vertebral cortex 1·9±1·8, and vertebral trabeculae 3·1±1·8 μg/g dry weight. For a patient with dialysis motor neuropathy significantly higher values were found. Comparison with values in the literature shows that our reference values are in agreement with published results obtained by flameless atomic absorption spectroscopy.
Isotope Dilution Analysis Using Chromatographic Separation of Isotopic Forms of the Compound to be Measured
Authors: Pratt J J
Published: February 2014

Using progesterone, testosterone, androstenedione, 11-oxoprogesterone and 11β-hydroxyprogesterone as models, a new form of isotope dilution assay has been developed. A known mass of deuterium-labelled steroid is added to the serum sample. High-performance liquid chromatography is used to separate endogenous steroid from its deuterium-labelled form. After separation, the two forms of the analyte are quantitated using conventional methods: radioimmunoassay, enzyme-linked immunoassay and, where the concentrations are high enough, ultraviolet light absorption. The ratio of the amounts of the two forms of the analyte is used to calculate the amount of unlabelled material in the original sample.

The assay principle is quite general. A variety of high resolution methods are available to separate isotopic analogues of the same compound. A number of detection methods can be used to quantitate the separated isotopic forms. Extension of this principle to other fields of interest in bio-medicine is discussed briefly.
Performance and Clinical Utility of a Commercially Available ‘C-terminal’ PTH Assay
Authors: Ingle A R , Bailey J E , Matthews H L , Harrop J S
Published: February 2014

The performance and clinical utility of a ‘C-terminal’ parathyroid hormone (PTH) radioimmunoassay (Dac-Cel, Wellcome Diagnostics) is described. Parathyroid hormone, as measured by the Dac-Cel method, is stable in whole blood samples for at least 24 h. 84% of patients with hypercalcaemia due to primary hyperparathyroidism have values above the upper limit seen in normocalcaemic subjects (0·5 μg/L), with detectable serum PTH demonstrable in the remaining 16%. In patients with hypocalcaemia due to hypoparathyroidism serum PTH was undetectable in 73% and ‘inappropriately’ low in the remainder. In 50% of patients with malignancy-associated hypercalcaemia serum PTH was undetectable, but was above 0·5 μg/L in 13%. Increased PTH concentrations were invariably found in patients with renal failure.

The Dac-Cel method is a reliable and robust technique for measurement of PTH and in conjunction with determination of calcium facilitates the diagnosis of primary parathyroid disorders. Caution is required in the interpretation of PTH measurements in patients with renal failure; the significance of detectable PTH in some patients with malignancy-associated hypercalcaemia is not clear.
The Assay of 4-Hydroxy-3-Methoxymandelic Acid in Urine by HPLC with Electrochemical Detection Using Bonded-Phase Silica Sorbents for Rapid, Simple and Selective Extraction
Authors: Holly J M P , Patel Naina
Published: February 2014

A method is reported for the determination of 4-hydroxy-3-methoxymandelic acid (HMMA) by HPLC with electrochemical detection. The preparation of sample prior to HPLC has been studied and an efficient and selective extraction procedure described. Bonded-phase silica extraction columns and a vacuum manifold were used for the simple and rapid processing of batches of urine samples. Combining a reverse-phase C18 and an anion exchange column ensures selective isolation of HMMA. This simplified greatly the subsequent chromatography. The method was combined into a simple scheme for the routine analysis of urine HMMA, catecholamines and 5-hydroxyindole-3-acetic acid. The HPLC was standardised such that a single mobile phase was used with minor modification for each of the assays.
The Use of Different Lipids to Express Serum Tocopherol: Lipid Ratios for the Measurement of Vitamin E Status
Authors: Thurnham D I , Davies J A , Crump B J , Situnayake R D , Davis M
Published: February 2014

Plasma tocopherol was measured in 85 alcoholic patients and 40 control subjects from a local factory. Cholesterol, triglycerides and phospholipids were measured individually and summed to give an estimate of total serum lipids. Plasma tocopherol concentrations of the alchoholics were significantly lower than those of the controls and showed wide variation from marked deficiency to the upper limit of the normal range. Using regression analysis, 1·11 μmol tocopherol/mmol total lipids were calculated as the threshold of deficiency equivalent to 0·8 mg tocopherol/g total lipid established by Horwitt et al.1 The sensitivity and specificity of other tocopherol:lipid ratios for identifying vitamin E deficiency was compared with the tocopherol:total lipid ratio. Thresholds of deficiency for the different tocopherol:lipid ratios were calculated. The tocopherol:cholesterol+triglyceride ratio was found to be almost as powerful in identifying vitamin E deficiency as the tocopherol:total lipid ratio (sensitivity 95%, specificity 99%). Of the tocopherol:individual lipid ratios, the tocopherol:cholesterol ratio gave the best results (sensitivity 86%, specificity 94%).
Mobile Phase Optimisation in the Separation of Antiepileptic Drugs by High-Performance Liquid Chromatography
Authors: Fry D E , Iqbal J , Christofides J A
Published: February 2014

A simple method is described for adjusting the mobile phase composition to obtain optimum separation of commonly prescribed antiepileptic drugs by high-performance liquid chromatography. The drugs are separated, in less than 6 min, on a column of Hypersil ODS 5 μm (100 mmx5 mm i.d.) with a high mobile phase flow rate. The final mobile phase composition is a mixture of methanol, acetonitrile, tetrahydrofuran and water, adjusted to give the best separation with our laboratory conditions. The method is described and evidence of precision and accuracy presented. The improved separation resolves the major metabolites of carbamazepine which have been ignored in most methods for antiepileptic drugs. The advantages of mobile phase optimisation to improve the separation of antiepileptic drugs are discussed.
Carnitine Concentrations in Dialysed and Undialysed Patients with Chronic Renal Insufficiency
Authors: Rodriguez-Segade S , De La Peña C Alonso , Paz M , Novoa D , Romero R , Arcocha V , Del Rio R
Published: February 2014

Free carnitine, acylcarnitine and total carnitine serum concentrations have been measured in chronic renal insufficiency patients under conservative treatment, in patients under regular haemodialysis treatment and in healthy controls. In the undialysed patients the levels of free carnitine, acylcarnitine and total carnitine were all clearly higher than those of the control group. The free carnitine and total carnitine levels of undialysed subjects were also higher than in regularly haemodialysed patients, showing that dialysis produces plasma carnitine losses that are not compensated for by endogenous synthesis of carnitine (this finding supports published reports of tissue carnitine deficiency in patients undergoing regular haemodialysis). The acylcarnitine levels of dialysed and undialysed patients were not significantly different, however; both were very much higher than that of control group. The hypercarnitinaemia of the patients under conservative treatment suggests that the impairment of renal function causes a reduction in the elimination of carnitine via the kidney.
Calcium, Vitamin D and Parathyroid Hormone Relationships in Pregnant Caucasian and Asian Women and Their Neonates
Authors: Okonofua F , Menon R K , Houlder S , Thomas M , Robinson D , O'Brien S , Dandona P
Published: February 2014

Plasma calcium, serum 25 hydroxyvitamin D [25(OH)D], 1,25 dihydroxyvitamin D[1,25(OH)2D] and parathyroid hormone (PTH) have been measured in pregnant and newborn Caucasians and Asians. Calcium and 25(OH)D concentrations were lower in Caucasian than in Asian women at all four stages (three trimesters and during labour) of pregnancy. PTH concentrations were greater in Asian than in Caucasian women during the three trimesters, but not at labour, and increased in both groups through pregnancy, without a concomitant change in plasma calcium concentrations. There was a significant inverse correlation between calcium and PTH, as well as 25(OH)D and PTH, concentrations. These data demonstrate the presence of progressive ‘hyperparathyroidism’ during pregnancy in Caucasian and Asian women. The higher PTH concentrations in Asian women may reflect the necessity of maintaining adequate plasma calcium concentrations through PTH-induced osteolysis in the face of vitamin D deficiency. Relative hyperparathyroidism in Asians may contribute to net loss of calcium from the skeleton and osteopenia in Asian women. Calcium, 25(OH)D and l,25(OH)2D concentrations were lower, and those of PTH higher, in Asian newborns compared with Caucasian newborns. Serum 1,25(OH)2D concentrations in the Asian newborn, though lower than respective maternal levels, were comparable with normal adult levels, indicating that 1,25(OH)2D biosynthesis is stimulated in the Asian newborn to compensate for the low serum 25(OH)D concentrations.
Does the Measurement of Serum Fructosamine Accurately Reflect Levels of Glycated Albumin in Insulin-Dependent Diabetes?
Authors: Winocour P H , Bhatnagar D , Reed P , Dhar H
Published: February 2014

We have measured serum glycated albumin (GSA) by affinity chromatography and immunoturbidimetry, and serum fructosamine using a Cobas FARA analyser in blood samples from 37 type I diabetics and 21 healthy controls. Random blood glucose and glycated haemoglobin levels were also measured.

Glycated haemoglobin (HbA1) correlated with glycated albumin and fructosamine in the diabetic group. A less clear relationship was found between glycated albumin and fructosamine. HbA1, GSA and fructosamine correlated poorly with random blood glucose levels.

These data indicate that serum fructosamine levels do not accurately reflect those of glycated albumin, as has recently been suggested, in type I insulin-dependent diabetics where glycaemic control fluctuates more than in type II diabetics. It is postulated that the two methods reflect varying glycaemic levels to a different degree, thereby accounting for the disparity.
Short-Term Effect of a 75 g Oral Glucose Load on Glycohaemoglobin Levels
Authors: Forrest Richard D , Jackson Caroline A , Gould Barry J , Casburn-Budd Marianne , Taylor Julie E , Yudkin John S
Published: February 2014

Two hundred and twenty-three subjects out of a total of 347 with various degrees of glucose tolerance were recalled after a screening survey for diabetes. They were a randomly selected sample of people over the age of 40 and they underwent a formal 75 g glucose tolerance test in order to assess the effect of a glucose load on glycohaemoglobin levels measured by four different assay methods.

Oral glucose loading was found to affect glycohaemoglobin levels only when these were measured by an agar-gel electrophoretic method that did not remove the labile aldimine-linked Schiff base fraction. The increase in glycohaemoglobin during the glucose tolerance test as estimated by this method was proportional to the 2 h blood glucose level. Glycohaemoglobin levels measured by agar-gel electrophoresis with elimination of the Schiff base, by affinity chromatography and by iso-electric focussing, were not affected by a 75 g oral glucose load. We conclude that blood samples for glycohaemoglobin assay may be collected at any time of the day, without regard to the subject's previous food intake, provided an assay method is used that removed the aldimine-linked labile fraction.
Investigations into Negative Interference by Jaundiced Plasma in Kinetic Jaffé Methods for Plasma Creatinine Determination
Authors: Knapp M L , Hadid O
Published: February 2014

Negative interference by jaundiced plasma in kinetic Jaffe methods for plasma creatinine determination is caused by both conjugated and unconjugated bilirubin. The amount of interference observed is method- and temperature-dependent and is directly related to bilirubin concentration but is independent of the creatinine concentration. Bilirubin also significantly reduces the precision of the creatinine estimation. A mechanism of bilirubin interference in kinetic Jaffé methods is proposed and the influence of picrate concentration, hydroxide concentration and temperature on the magnitude of bilirubin interference has been investigated.
An Improved Extraction Procedure for an HPLC Method for Cyclosporin a in Whole Blood and Plasma
Authors: Maguire S , Kyne F , Uaconaill D
Published: February 2014

Cyclosporin A (CyA) was assayed by high performance liquid chromatography (HPLC) following extraction of the whole blood or plasma with diethyl ether and chromatography on a Sep-Pak Silica cartridge. Using carefully chosen volumes and ratios of ethyl acetate and hexane in the eluting sequences on the Sep-Pak, the major interferent present in normal blood and serum was eliminated.
A High Performance Liquidc Chromatography Method for the Analysis of Total and Free Indomethacin in Serum
Authors: Roberts I , Smith I M
Published: February 2014

A simple rapid and sensitive HPLC technique for the analysis of total and free plasma indomethacin concentrations in neonates is described. The advantages of the technique are small sample volumes (50 μL) enabling the use of capillary samples, direct extraction, low limits of detection (20 ng/mL) and good precision (CV<7% between-batch). Indomethacin and the internal standard (flufenamic acid) eluted within 12 min and the peaks were unaffected by indomethacin metabolites or by a number of commonly used drugs. The technique is suitable for the investigation into the pharmacokinetics of total and free indomethacin, in neonates with patent ductus arteriosis, and could be used to define a therapeutic window for free indomethacin levels to enable therapeutic drug monitoring to occur in this condition.
Interference by Naproxen in the Urinary 5-Hydroxyindoleacetic Acid Assay is Due to a Metabolite, Desmethylnaproxen
Authors: Walker P L , Pettit B R , Sandler M
Published: February 2014

Interference by naproxen in the spectrophotometric assay for urinary 5-hydroxyindoleacetic acid has been investigated. Gas chromatography-mass spectrometry demonstrated that ingestion of naproxen was associated with the production of four urinary components, unchanged drug and three metabolites, the major one being desmethylnaproxen. Unlike naproxen, this metabolite reacted in the spectrophotometric assay giving a product with the same absorption spectrum as that observed in urine samples obtained after naproxen ingestion. Unlike 5-hydroxyindoleacetic acid, the colour due to desmethylnaproxen is thermolabile and so the interference may be overcome by performing the incubation at 100°C.
Bacterial Contamination of QC Specimens as a Cause of Artefactually Poor Performance in the UK EQAS
Authors: Kemp L R , Ferguson K M , Jeffcoate S L
Published: February 2014

During 1984–85, users of a solid-phase radioimmunoassay kit for LH and FSH had problems of both variability and bias in the assay of some EQAS specimens despite adequate internal QC. The cause has been identified as contamination of these specimens with Pseudomonas fluorescens.
Plasma Salicylate Analysis: A Comparison of Colorimetric, HPLC and Enzymatic Techniques
Authors: Jarvie D R , Heyworth R , Simpson D
Published: February 2014

Three colorimetric techniques and one enzymatic technique have been compared with an HPLC method for the analysis of salicylate in the plasma of patients after self-poisoning with aspirin. The enzymatic technique was specific but expensive to perform. The colorimetric techniques were simple, cheap and precise. The Keller method, however, was susceptible to interference from endogenous substances. We report a modification of the Keller method that eliminates most of this interference and improves the accuracy of the analysis. The new method is easier and safer to perform under emergency conditions than the Trinder technique.
Pulsatile Secretion of TSH in Healthy Subjects
Authors: Clark P M S , Clark J D A , Holder R , Raggatt P R , Wheatley T
Published: February 2014

The physiological variations in serum TSH concentration have been investigated using an enzyme amplified immunoassay with improved sensitivity and precision. Blood samples were collected at regular intervals from 10 healthy volunteers during the period 1800 h to 0100 h. Spectral analysis followed by periodic regression analysis demonstrated significant serum TSH pulsatility with periodicities of 60 or 85–100 min. In addition, a significant ( P < 0·001) evening rise in serum TSH concentration was demonstrated in all subjects, with levels rising at around 21·30–22·00 h.
Overestimation of Immunoglobulins in the Presence of Rheumatoid Factor by Kinetic Immunonephelometry and Rapid Immunoturbidimetry
Authors: Chambers Robin E , Whicher John T , Perry David E , Milford-Ward A , White Peter A E , Fifield Richard
Published: February 2014

The United Kingdom External Quality Assessment Scheme for Specific Proteins has demonstrated that one method group, comprised of kinetic immunonephelometric assays, gives significantly higher results for immunoglobulins in certain pathological sera containing rheumatoid factor. Using IgM as a model, we have compared kinetic immunonephelometry and a rapid (5 min incubation) immunoturbidimetric assay with radial immunodiffusion (RID) on seven sera. Compared with RID significantly higher results were obtained by kinetic nephelometry on all five sera positive for rheumatoid factor, and by turbidimetry on three of the four of these studied. In a serum with IgM increased due to primary biliary cirrhosis lower results ( P0·05) were obtained by nephelometry than by RID. The remaining serum was normal, and no significant intermethod differences were found. The possible causes for these discrepancies are discussed.
Chemiluminescence Immunoassay for Progesterone in Plasma Incorporating Acridinium Ester Labelled Antigen
Authors: Miller S A , Morton M S , Turkes A
Published: February 2014

A sensitive, solid-phase chemiluminescence immunoassay suitable for determining progesterone concentrations in plasma has been developed. The solid-phase antiserum was prepared by coupling a monoclonal progesterone-antibody, raised against a progesterone-11α-hemisuccinyl/bovine serum albumin conjugate, to cyanogen bromide activated cellulose. An 11α-progesteryl-2-carboxymethyltyramine-4-(10-methyl)-acridinium-9-carboxylate conjugate was used as the chemiluminescent label. The assay had a lower limit of sensitivity of 3 pg/assay tube and satisfied accepted validation criteria. Progesterone concentrations determined by chemiluminescence assay were in good agreement not only with a radioimmunoassay in routine use but also with a gas chromatography-mass spectrometry procedure.
Design of the Immunogen and Label for Use in a Fluoroimmunoassay for Paracetamol
Authors: Gallacher G , Coxon R , Landon J , Rae C J , Abukinesha R
Published: February 2014

The design of immunogens for raising antisera containing antibodies specifically directed against paracetamol is discussed. A derivative of the drug with minimal structural alteration was synthesised, coupled to the carrier protein key-hole limpet haemocyanin, and used to immunise sheep. The evaluation of the resulting antisera is described. Preparation of a fluorescent label with reduced bridge-binding then allowed the development of a polarisation fluoroimmunoassay for paracetamol in buffer, suitable for conversion to a direct serum assay.
HbA1 in the Diagnosis of Factitious Remission of Diabetes
Authors: Krentz A J , Hale P J , Albutt E C , Nattrass M
Published: February 2014

A case of factitious remission of type I diabetes in an adolescent girl is reported. The clue to diagnosis came from an inconsistency between clinic blood glucose levels and the corresponding values of glycosylated haemoglobin.

Investigations of 24 h hormone and metabolite profiles demonstrated discrepancies between insulin dose, endogenous insulin production and free insulin levels which provided confirmatory evidence of surreptitious self-administration of insulin by the patient.
Reduction of Neonatal Blood Eliminates the Error Induced by Oxygen Saturation in the Spectrophotometric Measurement of Carboxyhaemoglobin
Authors: Nicholson N A , Karabus C D , Klein M , Hartley P S
Published: February 2014

Blood carboxyhaemoglobin (COHb) is a sensitive index of haemolysis and has been used in assessing the cause of different types of neonatal jaundice. Although the introduction of automated spectrophotometry provides rapid and accurate measurement in adult blood, in neonates oxygenated foetal haemoglobin (HbF) is thought to interfere with COHb measurement. In an attempt to eliminate this problem, the haemoglobin in neonatal blood was reduced with sodium dithionite. Cord blood from 50 infants was measured before and after reduction using an IL-282 co-oximeter; COHb levels fell after reduction. A significant positive correlation was found between apparent COHb% and oxygenation of cord blood. In contrast, no significant correlation was found between these parameters in adult blood where COHb values remained the same or rose slightly after reduction. In 20 healthy non-icteric neonates the mean reduced blood COHb value was not significantly different from the mean COHb value of 23 healthy nonsmoking adults. We suggest that COHb in neonatal blood can be simply and accurately measured by the IL-282 co-oximeter provided that the blood is fully reduced.
A Simplified Scheme for the Investigation of Thyroid Function in Chronic Liver Disease
Authors: Bannister P , Shapiro L , Faye S , Bolton R
Published: February 2014

The investigation of thyroid disease in the presence of chronic liver disease (CLD) is difficult. Conventional tests are influenced by chronic illness and abnormal concentrations of binding proteins. A three tier system is normally used: thyroxine (T4), then T3 or TSH and an index for binding proteins. The recently introduced TSH immunoradiometric assays (IRMA) offer the potential of a single test assessment of thyroid function. This was assessed by the measurement of T4, T3, THBC and the free thyroxine indices in subjects with CLD. Conventional tests showed a high number of abnormal T4 values but binding indices were normal. The TSH-IRMA results were all normal. TSH-IRMA assays are rapid, easy to use and cheap. They remove the uncertainties in assessing thyroid function in CLD and may be the test of choice.
Creatine Determinations as an Early Marker for the Diagnosis of Acute Myocardial Infarction
Authors: Delanghe J , De Buyzere M , De Scheerder I , Vogelaers D , Vandenbogaerde J , Van Den Abeele A-M , Gheeraert P , Wieme R
Published: February 2014

In the acute phase of acute myocardial infarction (3–8 h after onset of symptoms) an early transient increase in the creatine concentration of serum, saliva, and especially of urine can be observed. Due to the renal threshold, urine values give a much better discrimination between infarction patients and controls than do serum determination. In some patients secondary peaks of serum and urine creatine concentrations can be seen about 24–36 h after hospital admission. Intramuscular injections of 5·0 mL of a saline solution and muscular trauma interfere with the test, but with angina pectoris interference is absent or limited. Creatine leakage from myocardium is insufficient to explain the observed creatinuria in infarctions, and intact extra-cardiac tissues are believed to be involved in creatine release.
The Relationship between Theophylline, Caffeine and Heart Rate in Neonates
Authors: Nadkarni S , Hay A W M , Faye S , Congdon P J
Published: February 2014

Plasma theophylline and caffeine levels were measured in neonates receiving aminophylline for apnoea. Significant levels of caffeine were present in neonates with high plasma theophylline levels and particularly in those children who had been on theophylline for 6 days, or more. Caffeine levels in plasma decreased slowly compared to theophylline.

Tachycardia did not occur in any infants even at theophylline values greater than 20 mg/L. For theophylline concentrations above 10 mg/L there was no relationship between heart rate and drug level. Heart rate alone cannot be used to predict toxic drug levels, and high drug levels will not necessarily cause tachycardia.