bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Assessment of the in Vitro Biopotency and Site(s) of Action of Drugs Affecting Adrenal Steroidogenesis
Authors: Lambert A , Frost J , Mitchell R , Robertson W R 
Published: February 2014

Dispersed guinea-pig adrenal cells have been employed in the in vitro estimation of the biological potency and sites of action of drugs acting against the adrenal. The effect of 12 drugs on cortisol secretion from cells stimulated with adrenocorticotrophin (ACTH, 50 ng/L, a 95% saturating dose) has been tested. All the drugs depressed cortisol output in a dose-related fashion. The concentration of drug which inhibited secretion by 50% was (μmol/L, mean±SEM): etomidate 0·1±0·002; epostane 0·44±0·02: 17-ketotrilostane 0·55±0·04: trilostane 1·3±0·1: metyrapone 3·5±0·6: cyproterone acetate 4·6±0·2: megestrol acetate 11±2: danazol 22±2: aminoglutethimide 41±5: stanozolol 50±4: thiopentone 160±18: propofol 170±18. The sites of the anti-steroidogenic effect of seven of these drugs have also been established using a method based upon the sequential stimulation by the exogenous precursor steroids of the various steps leading to the biosynthesis of cortisol by adrenal cells. Propofol acts between ACTH binding and pregnenolone production, trilostane, megestrol acetate and cyproterone acetate are 3β-hydroxysteroid dehydrogenase inhibitors whereas metyrapone, etomidate and thiopentone act at 11β-hydroxylase.
Analytical Goals for Glucose Analyses
Authors: Fraser Callum G 
Published: February 2014

Analytical goals may be defined as those standards of performance required to facilitate optimal patient care. Review of the considerable amount of published work on glucose analyses allows delineation of the following current goals: For plasma glucose: within-laboratory between-batch imprecision — CV≤2·2%; inaccuracy — no bias; linearity − 1 to 28 mmol/L; detection limit − 1 mmol/L; turnaround time − 30 min (in emergency situations). For urine glucose (quantitative): within-laboratory between-batch imprecision — SD ≤0·1 mmol/L; inaccuracy — no bias. for urine glucose (qualitative or semi-quantitative): negative — should be negative; positive — should be positive ± one positive colour block; detection limit − 2·8 mmol/L. Moreover, each laboratory should develop goals for the many pre-analytical factors affecting glucose analyses. While the above goals are not always achieved in current practice, they are attainable and are worthy targets to strive to reach. The general principles discussed here for glucose analyses are applicable to other analytes of interest to the clinical biochemist.
The Measurement of Insulin-Like Growth Factor I: Clinical Applications and Significance
Authors: Teale J D , Marks V 
Published: February 2014

Of the somatomedins so far measured, the selective quantitation of insulin-like growth factor I (IGF-I) appears to have the greatest potential in clinical diagnosis. There have been two approaches to the development of immunoassay systems. One type uses antibodies raised against synthetic fragments of IGF-I which exhibit cross-reactivity with the whole hormone. Such assay systems may be adequate for measuring normal adult plasma IGF-I levels, but the potential for the higher sensitivity required for detecting sub-normal plasma levels in young children is apparent only in methods using antibodies raised against the complete hormone. IGF-I in plasma exists as part of a high molecular weight complex in which it is bound to carrier proteins. The binding proteins may interfere with plasma IGF-I measurements by radioligand assays. Direct analysis of untreated plasma samples is claimed to be possible using disequilibrium assay conditions but in order to maximise assay sensitivity it is necessary to employ an initial extraction stage in order to eliminate binding protein interference. Whether the measurement of plasma IGF-I can or should be used in addition to, or as a replacement for, plasma growth hormone (GH) measurement in the clinical assessment of growth disorders remains a controversial issue. Available evidence indicates that a single, random plasma IGF-I level provides an accurate reflection of GH secretion. Adequate discrimination between the elevated levels in acromegaly and normal reference values has been demonstrated. However, in the investigation of growth-retarded children available radioimmunoassay (RIA) methods have proved only partially successful because of the age-related nature of normal plasma IGF-I concentrations. Existing assays appear capable of identifying sub-normal plasma levels after the age of approximately 4 years. In younger subjects an improvement in assay sensitivity is required in order to establish with greater accuracy the relevant normal ranges. Improvements in the identification of the particular lesion responsible for retarded growth in a child can be achieved by measurement of both plasma GH and IGF-I concentrations. The predictive value of the acute plasma IGF-I response to single-dose GH therapy may identify patients who will respond to long-term GH therapy. Better, more informed decisions on subsequent treatment may therefore be made. Apart from GH control, several other factors influence circulating IGF-I levels. Nutritional status can be assessed through reference to IGF-I analysis, overall catabolic or anabolic processes being associated with decreasing or increasing plasma IGF-I levels respectively.
Comparison of Three Parathyroid Hormone Assays
Authors: Nisbet Jennifer A 
Published: February 2014

The efficiency of three parathyroid hormone (PTH) assays in the diagnosis of primary hyperparathyroidism has been investigated. Two assays used commercial reagents and measured the intact hormone and middle region of parathyroid hormone and the third assay employed the antiserum AS 211/32. Although the intact and mid-molecule assays showed a greater increase in PTH above normal than the laboratory PTH assay, patients with proven primary hyperparathyroidism were not distinguished from healthy subjects in every case. The intact and in house assays gave elevated values in seven out of nine patients with proven hyperparathyroidism and the mid-molecule assay in eight out of nine assays. The intact PTH and in-house assays were more successful than the mid-molecule method in separating patients with primary hyperparathyroidism from those with hypercalcaemia due to malignancy.
The Interpretation of Bloodspot 17α-Hydroxyprogesterone Levels in Term and Pre-Term Neonates
Authors: Berry Janet , Betts P , Wood P J 
Published: February 2014

Bloodspot 17α-hydroxyprogesterone, plasma cortisol, plasma sodium and urinary 17α-hydroxyprogesterone, cortisol, sodium and creatinine levels were determined in 24 term and 32 pre-term infants on the third, eighth and fourteenth days of life. Pre-term infants, whether ‘well’ or ‘sick’, had significantly raised bloodspot 17α-hydroxyprogesterone levels (up to 158 nmol/L) compared with those found in term infants (up to 18·8 nmol/L). Urinary 17α-hydroxyprogesterone/creatinine ratios were also higher in pre-term infants. Plasma cortisol results showed similar ranges for term and pre-term infants, and bloodspot 17α-hydroxyprogesterone/plasma cortisol ratios for day 3 specimens correlated with the degree of prematurity. These results may be due either to immature enzyme systems in the pre-term baby or to an excess of related steroids cross-reacting in the 17α-hydroxyprogesterone assay. We propose the use of two distinct upper limits of normal of 20 nmol/L (term infants) and 200 nmol/L (pre-term infants), for the interpretation of bloodspot 17α-hydroxyprogesterone levels at the end of the first week of life.
Single-Reagent Polarisation Fluoroimmunoassay for Cotinine (a Nicotine Metabolite) in Urine
Authors: Hansel M C , Rowell F J , Landon J , Sidki A M 
Published: February 2014

A rapid, single-reagent, non-separation, non-isotopic immunoassay was developed for determining levels of the nicotine metabolite, cotinine, in urine. The single reagent was prepared by pre-mixing an appropriate dilution of sheep anti-cotinine serum with a fluorescein-labelled cotinine tracer. All normal reliability criteria were satisfied. The assay was found to be specific for cotinine and there was no cross reactivity with other available nicotine metabolites and structurally-related compounds. The results obtained correlated closely with those of an established radioimmunoassay. The assay was well-suited to application in the discrimination of active smokers from non-smokers (and passive smokers).
Assays for Prolactin: Guidelines for the Provision of a Clinical Biochemistry Service
Authors: Jeffcoate S L , Bacon R R A , Beastall G H , Diver M J , Franks S , Seth J 
Published: February 2014

This paper summarises the views of the authors on the provision of a prolactin assay service. We discuss the pathophysiology of prolactin secretion and the clinical indications that arise from that. We cover the rather complex issue of the definition of normal and elevated prolactin levels. From these considerations, certain guidelines on the analytical performance of prolactin assays and their provision in a clinical biochemistry service are given. The extent to which currently available methods and performance as revealed by the UK External Quality Assessment Scheme (EQAS) match these guidelines are described and certain conclusions are reached. Finally, probable future developments are briefly discussed. The main conclusions and recommendations are as follows: Reagents of appropriate quality are available to enable prolactin immunoassays to be provided in UK clinical biochemistry laboratories. These are provided either separately or in the form of kits from both commercial and NHS sources. There is no requirement for individual laboratories to undertake their own antiserum production or prolactin iodination. Acceptable performance (as defined using internal QC procedures and the UK EQAS) is achievable using these reagents/kits, although one commercial kit shows a consistent marked negative bias. Reference ranges, including ‘normal ranges’, show considerable between-centre variability. Many centres have not established their own ranges, even those using in-house methods. Reference ranges for use in clinical biochemistry laboratories are proposed in this report. Some general guidance on the provision of a prolactin service is given, although this does not differ in principle from that appropriate for other peptide hormone analytes. There is no evidence that centres with small workloads perform any worse than average, although it may be more cost-efficient for such centres to send the samples elsewhere. As with other peptide analytes, non-isotopic immunometric methodology is likely to replace current radioimmunoassay methods in the near future.
Automated Trichloroacetic Acid Precipitation Method for Urine Total Protein
Authors: Cheung C K , Mak Y T , Swaminathan R 
Published: February 2014

Urine total protein determination by a trichloroacetic acid (TCA) precipitation method was automated on a Cobas Bio centrifugal analyser. The assay measures the turbidity at 420 nm when a 50 μL sample is mixed with 150 μL of 30 g/L TCA at 25°C. Samples up to 5 g/L can be measured by this method and interference due to pigments and turbidity can be minimised by running a blank with 1.25% hydrochloric acid (HCl) instead of TCA. The standard curve is stable and can be stored in the microcomputer and used again. Within-assay precision (CV) varied from 2 to 4.6% and between-assay precision varied from 1.8 to 5.4%. Analytical recovery ranged from 95 to 106.5% and the results correlated well with those obtained by a manual TCA method ( r=0.98). The method is easy to perform and is considerably faster than the manual procedure, thus saving time and providing a faster turnround time.
Laboratory and Diagnostic Performance of a Coated Well Immunoradiometric Assay for Serum Thyrotrophin
Authors: Gow S M , Nicol K , Seth J , Caldwell G , Toft A D , Beckett G J 
Published: February 2014

A new, coated well immunoradiometric assay (IRMA) for thyrotrophin (TSH) in serum has been evaluated with a view to its use as a first-line test of thyroid function. The Amerwell TSH IRMA is simple, rapid to perform (2·5 h) and the assay sensitivity was 0·07 mU/L with a working range (intra-assay CV <10%) of 0·3–100 mU/L. The mean inter-assay CV was 6·6% for TSH concentrations of 0·30–30·7 mU/L. The method compared favourably with an in-house TSH radioimmunoassay and an alternative commercial IRMA. In consecutive referrals to a thyroid clinic all patients with overt hyperthyroidism ( n = 103) had undetectable TSH concentrations and in those with subclinical hyperthyroidism ( n = 14), TSH was undetectable in 10 and below the reference range in four. The 95% confidence interval for 63 euthyroid serum samples was 0·36–4·3 mU/L. All hypothyroid patients ( n = 20) had increased TSH concentrations. TSH concentrations in pregnancy did not differ significantly from euthyroid TSH values. From 1916 routine tests, 13 undetectable TSH values were found in which thyroid hormone levels were normal and the patients had no known thyroid disorder. The assay appears suitable as a first-line test of thyroid function, but further assessment in a routine laboratory setting is required.
The Variability and Dietary Dependence of Urinary Oxalate Excretion in Recurrent Calcium Stone Formers
Authors: Brown J M , Stratmann G , Cowley D M , Mottram B M , Chalmers A H 
Published: February 2014

Twenty-two recurrent calcium stone formers had 24-h urinary oxalate excretions on their home diets which were significantly greater than those of 30 normal subjects (0·48±0·23 mmol/d; mean±SD compared with 0·31±0·11; P<0·01). The stone formers also demonstrated marked day to day variability in oxalate excretion indicating that a single normal urinary oxalate measurement did not exclude significant hyperoxaluria at other times. On a hospital diet containing 1000 mg calcium per day, urinary oxalate excretion fell significantly from 0·48±0·23 mmol/d to 0·32±0·12; P<0·01. As the urinary calcium excretion in and out of hospital was similar, it seems unlikely that low calcium intake at home was responsible for the hyperoxaluria. All patients had recurrent symptomatic stone disease and had been advised to avoid foods rich in oxalate. Whilst poor compliance is a possible explanation for the variability in oxalate excretion, we believe it is more likely that there is an inadvertent intake of oxalogenic precursors in their diet. As normal subjects do not demonstrate hyperoxaluria on similar home diets, stone formers may have a metabolic defect in the handling of these precursors.
Urinary Excretion of Six Modified Nucleosides by Patients with Breast Carcinoma
Authors: Vreken P , Tavenier P 
Published: February 2014

In this preliminary study we investigated the urinary excretion of pseudouridine, 1-methyl-adenosine, 1-methyl-inosine, 1-methyl-guanosine, 2-methyl-guanosine and N2,N2-dimethyl-guanosine in 22 patients with breast carcinoma, 16 with metastases. In 88% of the patients with metastatic breast carcinoma, at least one nucleoside level was elevated above the reference range; in 69% of cases at least two nucleoside levels were elevated; whereas three patients had all the six modified nucleosides elevated. Of the six patients without metastases, only one had one modified nucleoside level that was elevated. The others showed no elevated levels. The probability of finding an elevated level of 1-methyladenosine in breast carcinoma is high, when metastasis is present.
Plasma Sodium and Potassium Measurement: Minimising ISE-Flame Differences Using Specimens from Patients
Authors: Russell Leslie J , Smith Stephen C H , Buckley Brendan M 
Published: February 2014

Experience in clinical chemistry of direct reading ion-selective electrode analysers for the measurement of plasma Na+ and K+ concentrations has shown that the results obtained on any specimen may vary significantly from one make of instrument to another. To overcome these differences, the European Working Group on ISEs of the IFCC Expert Panel on pH, Blood Gases and Electrolytes have proposed that instruments should be standardised to report Na+ and K+ concentrations in undiluted plasma to agree with flame emission spectrometry in samples with normal plasma water bicarbonate concentrations and normal pH. In designing and setting the calibration of a new ISE analyser for Na+ and K+, the Corning 614, the manufacturer has attempted to satisfy this proposal using a large number of specimens obtained from patients. This paper presents details of the procedure used and the results of an independent evaluation of its validity in routine clinical practice.
Sodium Measurements in the Presence of Paraproteins by Four Direct ISE Methods and Flame Photometry Compared
Authors: Burnett David , Ayers Gwendolen J , Rumjen Sherab C , Woods Terence F 
Published: February 2014

Sodium was determined by flame photometry and by direct potentiometry using four different systems (Ektachem DT60, Corning 614, Orion 1020 and Nova-1) in serum samples from patients with normal proteins and paraproteins. Flame photometric and direct potentiometric differences (ISE-flame), showed the expected relationship with total protein whether or not the sample contained paraprotein, an exception being the Ektachem DT60 on normal protein. With the exception of the Ektachem DT60 with samples with normal protein levels, correlation between different ISE-flame estimates was good. Differences between direct potentiometric measurements are probably more attributable to efforts made by manufacturers to relate them to flame photometric measurements in ‘normal samples’, than to the volume occupied by increased protein content. The apparent lack of influence of protein on ISE-flame for the Ektachem DT60 was shown to relate to the original external reference electrode salt bridge used. A second study showed that changing this fluid to an equi-transferrant high salt content caesium chloride based reference fluid partially unmasked the protein effect.
When and How Should We Measure Plasma Ammonia?
Authors: Green Anne 
Published: February 2014

Hyperammonaemia is associated with a high morbidity and mortality. It is important to diagnose as it is often treatable and perhaps, most importantly, may be genetically determined. Measurement of plasma ammonia is rarely necessary in adult medicine. In paediatrics, and particularly in the neonatal period, it is an important investigation in the diagnosis and often in the subsequent management of several inherited metabolic disorders. Patients with these disorders, particularly neonates, will deteriorate over a period of hours and investigation cannot wait. In these situations a plasma ammonia together with other investigations for metabolic disorders must be available urgently and arc sometimes necessary out of normal laboratory hours. Interpretation must take into account the age and maturity of the child as well as the clinical state and results of other investigations. If treatment is initiated, frequent monitoring of plasma ammonia may be required. Plasma ammonia can be reliably and conveniently measured using a specific ion-selective electrode system or an automated enzyme method. Screening using a microdiffusion method is not a satisfactory alternative to a quantitative assay. Plasma ammonia is no longer solely the province of the specialised paediatric laboratory, but should be part of the repertoire of every laboratory supporting neonatal or paediatric units. The threshold for accepting requests should be lower than at present if we are to prevent misdiagnoses. This paper was prepared at the invitation of the Clinical Investigation Working Party of the Scientific Committee of the Association of Clinical Biochemists, but does not necessarily reflect their views.
An Enhanced Chemiluminescence Enzyme Immunoassasy for Serum Oestradiol
Authors: Sankolli G M , Stott Raw , Thorpe G H G , Smith D , Rudd B T , Kricka L J 
Published: February 2014

Oestradiol in serum was determined with a simple enhanced chemiluminescent enzyme immunoassay. The assay is based on oestradiol labelled with horseradish peroxidase and the IgG fraction of an oestradiol antiserum coated on a black polystyrene microtitre plate. The enzyme activity of bound label was determined using a p-hydroxycinnamic acid-enhanced chemiluminescent reaction. The assay was sensitive (1·8 fmol/well), precise (intra- and inter-assay CV 4–10% and 8–12%, respectively for sample concentration in the range 122–1330 pmol/L) and showed good agreement with conventional radioimmunoassays ( r=0·99).
Salivary and Plasma Free Testosterone and Androstenedione Levels in Women Using Oral Contraceptives Containing Desogestrel or Levonorgestrel
Authors: Swinkels L M J W , Meulenberg P M M , Ross H A , Benraad Th J 
Published: February 2014

The effect of oral contraceptives (OC) containing a combination of ethinyloestradiol (EE2) and either desogestrel (Dg/EE2) or levonorgestrel (Lg/EE2) on plasma concentrations of sex hormone binding globulin (SHBG), total testosterone (T), free T, total androstenedione (A), free A and on salivary T and A concentrations have been studied. SHBG concentrations were higher in the Dg/EE2 group than in the Lg/EE2 group. Total T, measured by RIA with prior extraction and chromatography, is also higher in the Dg/EE2 group. Per cent free T was lower in the Dg/EE2 group. Plasma free T and free A concentrations were the same in both groups. However, free T and free A were significantly lower in the OC-groups than in controls. In contrast, by direct assay, no difference in total T was observed between the OC-groups. Since the per cent free T was lower in the Dg/EE2 group, it would be concluded that free T in the Dg/EE2 group is lower than in the Lg/EE2 group. Salivary free T and free A concentrations did not differ between control and OC-groups. There was good correlation between salivary and free hormone concentrations within each group. We conclude that the concentrations of androgens in saliva do not necessarily directly reflect their free concentrations in plasma.
The Use of an Intact Molecule Parathyroid Hormone Assay in Disorders of Calcium Metabolism
Authors: Bicknell E J , Van't Hoff W 
Published: February 2014

We present the results obtained using a 1–84 human parathyroid hormone (PTH) assay in patients with abnormal calcium metabolism. A normal range was established in a series of healthy volunteers. Patients with surgically proven hyperparathyroidism (HPT) showed increased PTH levels which were separate from the normal range. Patients with probable hyperparathyroidism and milder hypercalcaemia showed a raised median PTH level but the range overlapped with normal. Patients with hypercalcaemia of malignancy showed reduced PTH levels and these patients were readily differentiated from those with probable and proven HPT by the use of the assay. In patients with chronic renal failure PTH values ranged from normal to high, the PTH concentration was found to be correlated with plasma alkaline phosphatase, but not with plasma creatinine.
A Simple Improved Method for the Measurement of Cyclosporin by Liquid-Liquid Extraction of Whole Blood and Isocratic HPLC
Authors: Fletcher Stephen J , Bacchus Robby A 
Published: February 2014

The current HPLC methods of cyclosporin measurement have been reviewed and all aspects assessed. A simple isocratic C-18 reverse phase HPLC method with improved efficiency is described for the routine measurement of cyclosporin in whole blood. An alkaline ether extraction is followed by an acid wash, solvent evaporation and two hexane washes of the reconstituted extract. The turn-round time for a single sample is 1 h. Daily batches of up to 40 patient samples can be easily measured with this method. The results are compared with those from the Sandoz radioimmunoassay (RIA) method.