bluuebunny/crossref_metadata_2025 huggingface dataset:
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.
Erythrocyte Insulin Receptors following Myocardial Infarction in Non-Diabetic Subjects
Authors: Dodds Karen , Lamb Patricia , Pentecost Brian , Nattrass Malcolm
Published: February 2014

To determine whether changes in insulin receptors follow acute myocardial infarction, 10 non-diabetic patients were studied on admission to a coronary care unit and 24 h later. Erythrocyte insulin receptors were 86 (50–406) per cell [median (range)] initially and increased significantly to 203 (73–714). Maximum percent specific binding and 50% inhibition of tracer binding did not change significantly. Decreased receptor number after myocardial infarction may contribute to insulin resistance in the acute phase.
Magnesium and the Premenstrual Syndrome
Authors: Sherwood R A , Rocks B F , Stewart A , Saxton R S
Published: February 2014

Plasma and erythrocyte magnesium were measured in 105 patients with premenstrual syndrome (PMS) using a simple atomic absorption spectroscopy method. The erythrocyte magnesium concentration for the patients with PMS was significantly lower than that of a normal population. The plasma magnesium did not show this difference. The significance of this apparent cellular deficiency of magnesium is discussed.
Sensitive and Specific Bromocriptine Radioimmunoassay with Iodine Label: Measurement of Bromocriptine in Human Plasma
Authors: Bevan J S , Baldwin D , Burke C W
Published: February 2014

Plasma bromocriptine assays must have high sensitivity because plasma concentrations are low, and high specificity because bromocriptine is extensively metabolised. This paper describes the simple preparation of a radioiodine-labelled derivative of dihydroergocriptine and its use in a radioimmunoassay employing an antiserum directed against the intact bromocriptine molecule. The method could measure plasma bromocriptine at concentrations of 0.05 nmol/L, had between-assay coefficients of variation of less than 10% and was more convenient than previous assays using tritium radiolabels.
A Comparison of Five Curve-Fitting Procedures in Radioimmunoassay
Authors: Nisbet Jennifer A , Owen J A , Ward Gail E
Published: February 2014

Data obtained from routine analytical radioimmunoassays were processed using five curve-fitting procedures, viz. ‘Amersham’, single binding site, four parameter logistic, a linear logit-log and a polynomial logit-log. The polynomial logit-log procedure gave the best fit, but this was probably due to the inherent flexibility of this curve-fitting process since the analytical precision achieved with it was no better than what was obtained with most of the other procedures. A limited study failed to show that statistical weighting of data before curve fitting had any practical advantage.
Drugs as Probes of Organ Function: Evaluation of the Hepatobiliary Axis Using Oral Rifampicin and Novel High Performance Liquid Chromatography
Authors: Berg J D , Ruddock S , Allen-Narker R A C , Bradby G V H , Davis M , Buckley B M
Published: February 2014

Investigation of the uptake and metabolism of drugs by organs such as the liver may allow assessment of specific aspects of organ function. Rifampicin, when orally administered, is transported into the hepatocyte from portal blood and thence passes, with its deacetylated metabolite, into the systemic circulation and into bile. This paper reports an investigation of the pharmacokinetics of a sub-therapeutic oral dose of rifampicin in healthy subjects, in patients with cirrhosis and in subjects with Gilbert's syndrome. The areas under the plasma concentration curves (AUC) in patients with cirrhosis were significantly greater than in healthy subjects. Subjects with Gilbert's syndrome had decreased AUCs compared with healthy subjects and were clearly distinguished from patients with cirrhosis. Rifampicin concentration in serum was measured by HPLC using a novel direct injection technique.
Adaptation of Coenzyme Stimulation Assays for the Nutritional Assessment of Vitamins B1, B2 and B6 Using the Cobas Bio Centrifugal Analyser
Authors: Mount J N , Heduan E , Herd C , Jupp R , Kearney E , Marsh A
Published: February 2014

Adaptation of coenzyme stimulation assays for the nutritional assessment of thiamine, riboflavin and pyridoxine on the Cobas Bio centrifugal analyser are described. Whole blood was collected into acid-citrate dextrose, which preserves the erythrocytes, prior to assay for several days. Washed erythrocytes stored at −70°C and subsequently thawed, showed altered enzyme activities. The methods offer improved precision over existing procedures and take advantage of the high throughput capabilities of the instrumentation.
Quantitation of Apolipoprotein C-III in Normal and in Hyperlipaemic Serum Samples by Enzyme-Linked Immunosorbent Assay
Authors: Riesen Walter F , Sturzenegger Erich
Published: February 2014

A specific and sensitive Sandwich enzyme-linked immunosorbent assay (ELISA) for the quantitative determination of apolipoprotein C-III, a major apolipoprotein of human very low density lipoproteins is described. The assay is non-competitive and it uses the same affinity isolated sheep antibody both for coating the wells and as conjugate with alkaline phosphatase. Total serum apo C-III was determined in a normal population of 24 men and 21 women. The difference was not statistically significant. In both sexes apo C-III concentration correlated positively with the serum triglyceride levels. In patients with hyperlipoproteinemia, apo C-III levels were increased.
Improved Resolution of Cellulose Acetate Membrane Electrophoresis
Authors: Riches Pamela G , Kohn J
Published: February 2014

A simple modification to cellulose acetate membrane electrophoresis is described. The results are comparable to those achieved with agarose gels at high voltage.
Measurement of Ethylene Glycol (Ethane-1,2-Diol) in Biological Specimens Using Derivatisation and Gas-Liquid Chromatography with Flame Ionisation Detection
Authors: Flanagan R J , Dawling S , Buckley B M
Published: February 2014

Ethylene glycol in plasma, urine or dialysis fluid is analysed as the phenylboronate derivative by mixing with acetonitrile/acidified 2,2-dimethoxy-propane containing phenylboronic acid. After centrifugation, a portion of the supernatant is analysed directly by gas-liquid chromatography using a 3% OV-101 column at 150°C and flame-ionisation detection. Propane-1,3-diol is used as a reactive internal standard. The limit of accurate measurement is at least 0.1 g/L and the linear range extends up to 5.0 g/L. No sources of interference have been identified.
Estimation of Imprecision in Immunoassay Quality Assessment Programmes
Authors: Sadler W A , Smith M H
Published: February 2014

A computer was used to produce and store a large body of simulated thyroxine and thyrotropin radioimmunoassay results over wide concentration ranges. Sets of 24 results, designed to represent results returned to an external quality assessment survey, were randomly drawn from the stored results in order to compare limited data survey estimates of imprecision with the ‘true’ values obtained from the population data. Results show that estimation of an imprecision profile has advantages over the usual index of imprecision, but that neither form of estimate is particularly reliable when the available data is limited. Results suggest that survey organisers should place considerably less emphasis on results from any one survey and greater emphasis on analysing cumulative data and method comparison data.
Serum Protein Zone Electrophoresis—An Outmoded Test?
Authors: Whicher J T , Spence C E
Published: February 2014

The predictive value of plasma protein changes in disease is very largely unknown, as relevant clinical and laboratory studies are lacking. The usefulness of zone electrophoresis as a method of detecting a constellation of plasma protein changes is even less clear. With the advent of precise automated techniques for specific plasma protein measurement, zone electrophoresis has little to offer except in the identification and quantitation of paraproteins, where it is essential.
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.
Comparison of Horseradish Peroxidase and Alkaline Phosphatase-Labelled Antibodies in Enzyme Immunoassays
Authors: Beyzavi K , Hampton S , Kwasowski P , Fickling S , Marks V , Clift R
Published: February 2014

The periodate method was found to be most effective for preparing horseradish peroxidase-sheep anti-human and horseradish peroxidase-donkey anti-mouse immunoglobulin (IgG) conjugates. The conjugates were improved by carrying out the oxidation of the enzyme at low pH. Anti-human and anti-mouse IgG-peroxidase conjugates (0·5 mg/mL IgG and 0.7 mg/mL 19G, respectively) were used at 1:15 000 and 1:8000 dilutions, respectively, in a sandwich ELISA to detect human and mouse IgG in buffer or in a growth medium containing 20% foetal calf serum. Using the peroxidase conjugates, it was possible to detect human and mouse IgG at concentrations as low as I ng/mL. The glutaraldehyde method was found to be much more effective than the periodate method for conjugating alkaline phosphatase to the antibodies. The optimum dilutions for anti/human and anti-mouse IgG-alkaline phosphatase conjugates (0.18 mg/mL IgG and 0.3 mg/mL IgG, respectively) in ELISA were 1:500 and 1:1000, respectively. The detection limit with alkaline phosphatase conjugates was 7 ng/ml for human IgG and 4 ng/ml for mouse IgG.
Reduced Leucocyte Zinc and Albumin-Bound Zinc in Blood of Haemodialysis Patients
Authors: Foote John W , Hinks Lesley J
Published: February 2014

The total, albumin-bound, and α2-macroglobulin-bound zinc concentrations in serum samples obtained from 20 haemodialysis patients have been measured. Blood leucocyte zinc contents were also determined. The total serum zinc concentrations in these samples were low, and in each case this was due to reduction in the zinc associated with albumin, although the concentrations of albumin itself were normal. There was no abnormality of the zinc bound to α2-macroglobulin. These data demonstrate a disturbance of the plasma transport of zinc in haemodialysis patients which might be due either to a reduced affinity of albumin for zinc in uraemic subjects, or the result of zinc deficiency. The zinc contents of white blood cells were also significantly reduced, supporting the possibility that these patients were indeed zinc deficient.
Total IgE and Allergen-Specific IgE Assays: Guidelines for the Provision of a Laboratory Service
Authors: Fifield R , Bird A G , Carter R H , Ward A M , Whicher J T
Published: February 2014

The Analytical Methods Working Party of the Association of Clinical Biochemists (ACB) established this Task Force to consider the measurement of total serum IgE and specific IgE. The aims were to give general guidance on available methods of assay; to survey commercial kits and ‘in-house’ methods; to investigate performance based on external Quality Assessment and independent evaluation, and to advise on criteria laboratories should consider before setting up IgE and specific IgE assays.
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.
Some Observations on the Nature of the Calcium-Cresolphthalein Complexone Reaction and its Relevance to the Clinical Laboratory
Authors: Corns Cathryn M , Ludman Clifford J
Published: February 2014

The reasons for the non-linearity of the standard curve for the calcium-cresolphthalein complexone reaction have been investigated. Calcium forms both 1:1 and 2:1 complexes with cresolphthalein complexone; at low calcium concentrations the 1:1 complex predominates and causes non-linearity. At high calcium concentrations the cresolphthalein complexone concentration becomes limiting, resulting in flattening of the calibration curve. It is recommended that two-point calibration of the assay be performed using a low calcium standard rather than setting on the baseline.
A Soluble-Phase Proinsulin Radioimmunoassay and its Use in Diagnosis of Hypoglycaemia
Authors: Naylor B A , Matthews D R , Turner R C
Published: February 2014

A soluble-phase proinsulin assay has been developed which does not require solid-phase antibody-binding. A human proinsulin standard curve is prepared in insulin-free and proinsulin-free plasma for comparison with unknown plasma samples. Proinsulin and insulin are bound with excess anti-insulin antiserum, and free C-peptide is removed by charcoal adsorption. The supernatant is then assayed using a routine C-peptide radioimmunoassay which utilises anti-C-peptide antiserum. The sensitivity of the assay (2 standard deviations above zero) is 9 pmol/L using 200 μL plasma sample. The assay is free from insulin cross-reactivity up to 100 mU/L and C-peptide up to 2000 pmol/L. Between-assay CV is 13% at 100 pmol/L. The assay has been used in subjects with hypoglycaemia of various aetiologies and has shown that a raised plasma proinsulin in the presence of hypoglycaemia can occur in sulphonylurea-induced and reactive hypoglycaemia as well as in insulinomas. After hyperglycaemic clamps at 7·5, 10 and 15 mmol/L glucose, type II diabetics both on and off sulphonylurea, were found to have lower proinsulin concentrations compared with normal subjects, commensurate with the diabetics' lower insulin responses.
The Raising and Characterisation of Antibodies to Salicylate
Authors: Bennett A P , Gallacher G , Landon J
Published: February 2014

Polarisation fluorescence was used to assess the antibody response in sheep immunised with 4-aminosalicylic acid coupled to keyhole limpet haemocyanin and to develop a polarisation fluoroimmunoassay for subsequent clinical use. The fluorescent label was prepared by coupling 4-aminosalicylic acid to fluorescein isothiocyanate. All immunised sheep produced antibodies and a simple assay was developed using salicylic acid as the standard. The simple fluorescence polarisation approach enabled the rapid and direct study of the immuno-reactivity of a large number of pure chemical analogues of salicylic acid. Each was assessed for its ability to compete with the fluorophore-labelled analyte for antibody-binding sites, relative to salicylate, thereby enabling investigation of the steric and chemical characteristics important in the recognition and binding of a hapten to antibodies.
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.
The Oral Glucose Tolerance Test—An Assessment of the Quality of its Performance
Authors: Wiener K
Published: February 2014

By means of a questionnaire, an attempt was made to assess the quality of performance and interpretation of the oral glucose tolerance test by laboratories participating in the UK External Quality Assessment Scheme for Clinical Chemistry. The results showed a general awareness of current recommendations in terms of both protocol for the test and criteria for interpretation of results, but some deficiencies were observed in both these areas and in some case deviations in protocol may have been sufficient to invalidate comparison of results with currently recommended criteria for interpretation of the test.
The Value of HbA1 and Fructosamine in Predicting Impaired Glucose Tolerance—An Alternative to OGTT to Detect Diabetes Mellitus or Gestational Diabetes
Authors: Salemans T H B , Van Dieijen-Visser M P , Brombacher P J
Published: February 2014

Glycosylated haemoglobin and glycosylated serum protein concentrations (fructosamine) have been monitored in patients suspected of diabetes mellitus ( n = 183), in pregnant women suspected of gestational diabetes ( n = 250) and in control groups ( n = 184). The response to the standard 75 g oral glucose tolerance test was used to confirm or reject the diagnosis, using different criteria for detection of diabetes mellitus compared to detection of gestational diabetes. A slightly higher sensitivity was observed for fructosamine compared to glycosylated haemoglobin to detect impaired glucose tolerance (52 vs 44%) or gestational diabetes (17% vs 8%). For detection of diabetic oral glucose tolerance no difference was observed between glycosylated haemoglobin and fructosamine; sensitivity for both parameters was 67%. The results suggest that fructosamine is slightly more sensitive in detecting borderline-abnormal glucose tolerance, whereas no differences are observed for detection of clearly abnormal oral glucose tolerance tests.
Glycated Haemoglobin Analyses—Assessment of within- and between-Laboratory Performance in a Large UK Region
Authors: John W G
Published: February 2014

The performance of glycated haemoglobin methods has been assessed in 20 laboratories. The methods used in these laboratories were affinity chromatography, electroendosmosis and ion-exchange chromatography. Assessment was based on the results returned by the participating laboratories on distributed specimens. Each method displayed acceptable precision and good linearity. Overall there were substantial differences in results reported by different laboratories, though within each method group these differences were less marked.
Serum Free Thyroxine and Free Triiodothyronine Concentrations in Healthy Fullterm, Preterm and Sick Preterm Neonates
Authors: John Rhys , Bamforth Fiona J
Published: February 2014

There are few data available on free thyroid hormone concentrations in the early neonatal period. With the widespread application of screening procedures for detecting congenital hypothyroidism there is a need for reference ranges in neonates. In this study we have evaluated thyroid function in healthy fullterm and preterm neonates, and sick neonates all within one to 10 days postnatal age. Our data indicates that free thyroxine but not free triiodothyronine is higher in fullterm neonates than the adult reference range and that both free thyroid hormone concentrations are reduced in healthy and sick preterm neonates as compared to fullterm neonates. Assessment of thyroid function in the early neonatal period needs to take into account these changes particularly in preterm and sick preterm neonates.
Retinol Binding Protein as a Small Molecular Weight Marker of Renal Tubular Function in Diabetes Mellitus
Authors: Rowe D J F , Anthony F , Polak A , Shaw K , Ward C D , Watts G F
Published: February 2014

A radioimmunoassay has been developed for the measurement in urine of retinol-binding protein (α2-roglobulin) and used as an index of renal tubular function in adult Type 1 (insulin-dependent) diabetics and to define reference ranges in non-diabetic controls. There was a significantly greater excretion ( P < 0·001) of retinol-binding protein in the diabetic group compared to the controls in both overnight and daytime samples. There was a weak positive correlation with albumin excretion ( r = 0·33; P < 0·01) but no correlation with HbA1, duration of diabetes or arterial blood pressure. The results indicate that retinol-binding protein excretion may be increased in diabetic subjects without increased albumin excretion. The possibility therefore exists that renal tubular damage may occur early in diabetic nephropathy without apparent glomerular dysfunction.
Rapid Measurement of Anticonvulsant Drug Concentrations in the Out-Patient Clinic, Using HPLC with Direct Injection of Plasma
Authors: Berg Jonathan D , Buckley Brendan M
Published: February 2014

A manual column-switching technique is described for the measurement of phenytoin, phenobarbitone, carbamazepine, and carbamazepine 10,11-epoxide. The analytical system is designed to be portable for use at the out-patient clinic and comprises an isocratic pump, UV detector and injection valve, together with a preparation column. Diluted plasma or serum is injected, without pre-extraction, onto a preparation column which replaces the sample loop on the injection valve. After washing unwanted material to waste, the preparation column is switched in-line with the analytical column, where separation of analytes occurs. The precision, accuracy and carryover of this extra-laboratory system are comparable with those obtained with laboratory-based immunoassay systems. Operation of the system allows the reporting of results within 5 min of sample injection and requires no specialist skills. The technique should be of particular interest to district general hospital laboratories where workload does not justify the cost of an automated HPLC system as the total capital cost is comparable to that of a portable glucose analyser. In contrast to immunoassay systems consumable costs are minimal. The equipment is easy to transport and may be used in the out-patient department to provide an analytical service similar to that provided for the determination of prothrombin time at the anticoagulant clinic.
The Effect of Haemolysis on the Measurement of Plasma Alkaline Phosphatase Activity
Authors: Grosset A , Knapp M L , Mayne P D
Published: February 2014

The non-dialysable fraction of haemolysate causes an apparent reduction of plasma alkaline phosphatase (ALP) activity using 4-nitrophenylphosphate as substrate. Analyses using four different buffers showed that the decrease in enzyme activity is affected by the buffer used. The percentage reduction in ALP activity is dependent on the initial ALP activity but not on the isoenzyme present. When diethanolamine was used as buffer, sample blanking almost completely compensated for the apparent reduction in enzyme activity. However, when aminomethylpropanol, aminomethylpropanediol and tris-carbonate buffers were used, it appeared that haemolysate reduced the catalytic activity of the enzyme, since sample blank correction had minimal effect on the results.
A Simple Side-Room Test to Screen for ‘Microalbuminuria’ in Diabetes Mellitus
Authors: Hodgson B W , Watts G F
Published: February 2014

A simplified latex bead immunoagglutination test is described employing the use of commercial antibody. It is practicable, reproducible and valid in screening for ‘microalbuminuria’ in diabetic patients. Although it is recommended as a side-room test its use should be supplemented where indicated by laboratory-based measurements.
A New Colorimetric Method for the Measurement of Serum Calcium Using a Zinc-Zincon Indicator
Authors: Corns Cathryn M
Published: February 2014

A new method is described for the measurement of serum calcium. Calcium in the sample displaces zinc from an EGTA complex, the zinc then forming a blue-coloured complex with a zincon indicator. The method is rapid, sensitive and linear; it may be applied directly to serum and is readily automated. No compound tested gave rise to any interference at physiological concentration, although excessive haemolysis leads to low results being obtained. To avoid interference from endogenous zinc a serum blank is required for each sample; this also avoids errors introduced by turbidity of the sample. The results obtained correlate well with atomic absorption spectroscopy ( r = 0·935, y = 1·12 x–0·28, n = 68).
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.
Erythrocyte Fatty Acid Profiles in Patients with Bronchogenic Carcinoma
Authors: Taylor A , Manche A , Wilson I , Watson D , Pandov H , Lawson N
Published: February 2014

The use of the erythrocyte stearic:oleic acid ratio in the diagnosis and prognosis of bronchogenic carcinoma has been assessed. Although there was a significant difference ( P<0·02) in the erythrocyte stearic:oleic acid ratio between bronchogenic carcinoma patients and healthy adults, the large overlap observed in the two groups rendered the test unsuitable for the diagnosis of malignancy. Furthermore, there was no consistent rise in this ratio after surgical resection, indicating the test to be of little prognostic use. A new explanation for the lower stearic:oleic acid ratios in certain patients has been postulated.
Sensitive Homologous Radioimmunoassay for Human Parathyroid Hormone to Diagnose Hypoparathyroid Conditions
Authors: Zillikens D , Armbruster F P , Stern J , Schmidt-Gayk H , Raue F
Published: February 2014

A sensitive radioimmunoassay for human parathyroid hormone (hPTH) to diagnose hypoparathyroid conditions is described. The antiserum was raised in goats against extracted hPTH. Synthetic human PTH fragment (53–84) is used as a standard and 125I-Tyr52hPTH (53–84) as a tracer. After a two-step incubation (24 h+24 h) at 4°C, the bound and free fractions are separated by a mixture of second antibody and polyethylene glycol solution. The detection limit for hPTH (53–84) is 2 pmol/L hPTH (53–84) (2 mol/tube). The PTH level in 36 healthy subjects was 5–12 pmol/L. Of 14 patients with hypoparathyroidism 11 patients had PTH concentrations below normal, two patients had levels on the lower limit of the normal range (5 pmol/L). The concentration of one patient with pseudohypoparathyroidism was markedly elevated. This assay is suitable for detecting low PTH levels and for studying changes of PTH concentration within the normal range.
Development of a Direct Fluoroimmunoassay for Serum Levels of 17-Hydroxyprogesterone
Authors: El-Gamal B A , Eremin S A , Smith D S , Landon J
Published: February 2014

A direct, rapid and highly specific fluoroimmunoassay for determining serum levels of 17-hydroxyprogesterone has been developed. It is based on the use of a sheep antiserum covalently coupled to magnetisable particles and fluorescein-labelled steroid. Sodium salicylate is employed to eliminate interference from endogenous binding proteins in serum. The sensitivity of 0·5 nmol/L is adequate for clinical purposes. Analytical recovery, linearity and precision are satisfactory and the results obtained correlate closely with those of an established radioimmunoassay using 3H-labelled steroid and the same antiserum after initial sample extraction and chromatography. The values found for serum from normal adult subjects ranged from 1·0 to 12·6 nmol/L while those from treated and untreated patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency were 1·5 to 190 and 28·0 to 655 nmol/L, respectively.
Development of a Specific Polarisation Fluoroimmunoassay for Paracetamol in Serum
Authors: Coxon Ruth E , Gallacher G , Landon J , Rae Christine
Published: February 2014

A specific polarisation fluoroimmunoassay for the measurement of paracetamol levels in serum has been developed for use in emergency toxicological screening. It is based on the use of a fluorescein-labelled analogue and a sheep antiserum and exploits the rapid dissociation kinetics of the hapten-antibody complex to enable the label and antiserum to be combined as a single reagent. Paracetamol levels are determined by adding 5 μL of serum to 1·5 mL of the single reagent, incubation at ambient temperature for a few minutes and measurement of fluorescence polarisation. In addition to its speed and simplicity, the assay is both accurate and precise and the results obtained correlate closely with those from the commonly used chemical and enzymatic techniques.
Neurone Specific Enolase in Amniotic Fluid: A Potential Marker of Anencephaly
Authors: Spencer K , Carpenter P
Published: February 2014

Normal values for neurone specific enolase in amniotic fluid have been found to follow a non gaussian distribution with a 1–99 centile range of 1·10–4·32 μg/L. Neurone specific enolase levels have been shown to be raised in the amniotic fluid of pregnancies complicated by anencephaly, although not those complicated by open spina bifida. Neurone specific enolase measured by radioimmunoassay is capable of totally discriminating between normal pregnancies and those complicated by anencephaly. The study demonstrates the possible value of investigating other neuronal proteins which may find value as adjuncts to amniotic fluid Alpha fetoprotein levels in the prenatal diagnosis of Neural Tube Defects.
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.
Diagnosis of Familial Hypercholesterolaemia Using DNA Probes for the Low-Density Lipoprotein (LDL) Receptor Gene
Authors: Armston A E , Iversen S A , Burke J F
Published: February 2014

Familial hypercholesterolaemia (FH) is one of the most commonly inherited diseases. It is characterised by an abnormal LDL receptor resulting in a selective elevation of serum LDL and cholesterol levels. The correlation between FH and premature heart disease means that these patients contribute significantly to the number of individuals presenting with coronary heart disease. In the work described here cDNA probes to LDL-receptor were used to assess the usefulness of recombinant DNA technology to diagnose familial hypercholesterolaemia. A 3′ probe to the LDL-receptor which detects a restriction fragment length polymorphism (RFLP) in linkage disequilibrium with normal and mutant LDL-receptor genes, was found to be potentially informative in 20% of the families studied. In addition a 5′ probe to the LDL-receptor may be capable of directly detecting mutations in some 6% of families. We suggest that until further work has established other RFLP's or oligonucleotide probes are synthesised to directly detect mutant LDL-receptor genes, recombinant DNA technology is only of limited value for diagnosing familial hypercholesterolaemia.
Determination of Cholesterol and Triglycerides in Blood: A Comparison between Wet Chemistry Methods and a Dry Chemistry Analyser
Authors: Seftel H C , Panz V R , Baker S G , Joffe B I , Mendelsohn D
Published: February 2014

Total cholesterol and triglyceride concentrations in 127 samples of capillary and venous blood were measured with the portable Reflotron ‘dry chemistry’ reflectometer and compared with serum levels measured in the laboratory using wet chemistry methods. Results were grouped into low, middle and high ranges. Levels measured with the Reflotron correlated closely with those measured by wet chemistry methods. Reflotron values for both lipid fractions were, however, consistently higher than wet chemistry levels but the differences were small except at high levels. It is concluded that the Reflotron is a satisfactory instrument for providing clinically useful measurements of cholesterol and triglyceride nearer to the patient.
Identification of Factors Limiting the Accurate Measurement of Plasma D-Penicillamine in Rheumatoid Arthritis Patients
Authors: Webb Brian A , Richardson Stephen J , Haslock Ian
Published: February 2014

Free and total reduced concentrations of D-penicillamine have been measured in the plasma of rheumatoid arthritis patients by HPLC and electrochemical detection. A reverse-phase ion-pair separation in conjunction with a dual porous graphite electrode satisfied the requirements of robustness, sensitivity, selectivity and suitable retention time. Plasma levels measured between 1·5 and 3 h after an oral dose, were <0·3 to 57·6 μmol/L and 0·6 to 85·0 μmol/L ( n=26) for free and total reduced drug concentrations, respectively. Sources of error in the accurate measurement of peak plasma D-penicillamine levels were identified as oxidative loss and alteration in the free to protein-bound ratio in the period following sample collection.
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.
Urinary Excretion of HMMA and HVA in Infants
Authors: Dale G , McGill A C , Seviour J A , Craft A W
Published: February 2014

Gas chromatography with flame ionisation detection has been used to establish the normal urinary excretion values of homovanillic acid and 4-hydroxy-3-methoxymandelic acid in 808 infants aged 6 months. This study, the essential pre-requisite for population screening for neuroblastoma in babies, reveals a mean homovanillic acid of 10·9 μmol/mmol creatinine and mean 4-hydroxy-3-methoxymandelic of 6·8 μmol/mmol creatinine. The upper 95% confidence interval were 25·5 μmol/mmol creatinine for homovanillic acid and 15·0 μmol/mmol creatinine for 4-hydroxy-3-methoxymandelic. Gas chromatography/mass spectrometry analysis of the 39 samples, (4·8%) with apparent increased excretion of one or both metabolites, revealed that this was, in each case, due to interfering peaks on chromatography.
Effects of Long-Term Haemodialysis on Lipid, Lipoprotein and Apolipoprotein Levels of Black Patients with Chronic Renal Failure
Authors: Rifai Nader , King Mary E , Sica Domenic A
Published: February 2014

Premature coronary artery disease is believed to be a major cause of death in patients undergoing long-term haemodialysis. We investigated the effects of chronic maintenance haemodialysis on lipid, lipoprotein and apolipoprotein levels of 42 black patients with chronic renal failure and compared them with those of 40 age- and sex-matched black controls to determine the changes in the lipoprotein profile and their possible contributions to increased risk of coronary heart disease in these patients. There were increases in triglyceride levels and in total/high density lipoprotein cholesterol ratios and decreases in high density lipoprotein cholesterol, in LDL cholesterol, in apolipoprotein AI and in apolipoprotein All in haemodialysis patients in comparison to controls. No significant differences were observed in any of the lipid, lipoprotein and apolipoprotein levels between male and female patients and between patients receiving anti-hypertensive therapy and those who were not. Our findings suggest that haemodialysis and/or events associated with maintenance dialysis may contribute to unfavourable variations in lipoprotein metabolism and, in turn, the increased mortality from coronary artery disease in this patient population.
An Automated Method for the Kinetic Measurement of Ferroxidase Activity
Authors: Winkles J , Jones A F , Winyard P , Blake D R , Lunec J
Published: February 2014

The oxidase activity of caeruloplasmin towards Fe II (ferroxidase) appears to be of physiological significance both in iron metabolism and as a serum anti-oxidant. We have developed an automated assay for ferroxidase using a centrifugal analyser. The method is quick and precise, and is not subject to interference by haemolysis, jaundice or lipaemia. Ferroxidase activities correlate significantly with caeruloplasmin and copper concentrations. Normal reference ranges have been measured.
The Effect of an Acute Phase Response or Pregnancy on Plasma Alpha-1-Antitrypsin Concentrations in Persons with Various S and Z Phenotypes
Authors: Barr Anne E , Cole Donald A , Clague Alan E
Published: February 2014

We have investigated the effect of an acute phase response on the plasma concentrations of alpha-1-antitrypsin (α1AT) in various phenotypes. Ninety seven per cent of patients with an acute phase response or pregnant patients who had an MS, MZ, S or SZ phenotype had α1AT levels within or above the reference interval of patients with the M phenotype who did not have an acute phase response. Thus a ‘normal’ concentration of plasma α1AT cannot be used to exclude even an S or SZ phenotype if the patient is pregnant or has an acute phase response.
Bone Density and Cortical Thickness in Nutritional Vitamin D Deficiency: Effect of Secondary Hyperparathyroidism
Authors: Fonseca V , Agnew J E , Nag D , Dandona P
Published: February 2014

Measurements of bone mineral index, mean metacarpal cortical thickness, plasma calcium, alkaline phosphatase and serum 25-hydroxyvitamin D and parathyroid hormone concentrations were carried out in 39 Asian vegetarian patients with hypovitaminosis D. It was concluded that PTH is probably the major determinant of osteopenia in patients with osteomalacia and secondary hyperparathyroidism; and that the presence of secondary hyperparathyroidism in association with hypovitaminosis D should be an absolute indication for vitamin D supplementation even in asymptomatic patients.
Diagnostic Limitations of Region-Specific Parathyroid Hormone Assays in the Investigation of Hypercalcaemia
Authors: Ashby J P , Thakkar H
Published: February 2014

Assays for N-terminus, C-terminus and mid-molecule parathyroid hormone have been assessed with respect to their sensitivity and specificity in the diagnosis of primary hyperparathyroidism (1° HPT). The mid-molecule assay was the most sensitive method studied and only failed to identify one out of 30 patients with histologically proven 1° HPT. In all three assays there was some degree of overlap between results observed in 1° HPT and in patients with non-parathyroid hypercalcaemia, with results in the latter group sometimes falling well within the hyperparathyroid range. This study highlights the limitations of currently available methods and emphasises the need for caution in the interpretation of parathyroid hormone (PTH) measurements.
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).