Search PubMed⌕ Search

Biomedical subjects

J W Kane

Publications and source records attributed to J W Kane.

At least 19 recordsLinked to original sources
PubMed2006

Dehydroepiandrosterone sulphate interferes with the Abbott Architect direct immunoassay for testosterone.

BACKGROUND: There are known difficulties in measuring testosterone in women using 'direct' (non-extraction) immunoassays. The positive bias encountered in many of these assays has been attributed to an unidentified interfering substance. We have evaluated the potential for dehydroepiandrosterone sulphate (DHEA-S) to cross-react in the Abbott Architect testosterone assay. METHODS: Samples (n = 81) from female patients who had DHEA-S, direct and extracted testosterone measured were examined retrospectively. Possible cross-reactivity was evaluated by spiking both testosterone free assay diluent and serum from a woman with exogenous DHEA-S. RESULTS: The retrospective patient analysis of the data demonstrated a relationship between interference and DHEA-S (r = 0.78, P < or = 0.0001). Spiking studies revealed a linear relationship between added DHEA-S and the measured testosterone concentration. Consistent with the retrospective study, for every 1 micromol/L increase in DHEA-S, 0.23 nmol/L of testosterone was measured in the diluent. Spiking DHEA-S into serum gave only a 0.12 nmol/L increase in measured testosterone for every 1 micromol/L rise in DHEA-S. CONCLUSION: DHEA-S cross-reacts in the Abbott Architect direct immunoassay for testosterone to a clinically significant effect. This cross-reactivity is likely to be responsible for much of the interference observed when measuring testosterone in women by this method.

Cross Reactions↗
PubMed2006

Investigation into possible causes of interference in serum testosterone measurement in women.

BACKGROUND: Direct (non-extracted) testosterone immunoassays may give spuriously high results in women. The presumed interferents may be removed if testosterone is extracted into an organic phase before being measured. We aimed to clarify possible causes and effects of interference in testosterone measurement in women. METHODS: Women who had a blood sample referred to Hope Hospital Clinical Biochemistry laboratory for measurement of serum testosterone concentration over a six-month period were studied. Clinical and treatment data were recorded. A difference (direct-minus-extracted testosterone) of less than 1.0 nmol/L was used to define a group with low interference. A difference of 2.5 nmol/L or more was used to define a group with significant interference. RESULTS: The distribution of interference in 1271 serum samples from female patients was unimodal. There were no group differences in clinical presentation or treatment. The median degree of interference was 1.4 nmol/L. In 42 female patients with varying degrees of interference, identified on routine assay, regression analysis showed strong association between dehydroepiandrosterone sulphate (DHEA-S) and interference (direct-minus-extracted testosterone) (r = 0.77, P < 0.001). CONCLUSIONS: Given that DHEA-S is present in very variable amounts in blood, it is possible that even with a low cross reactivity, DHEA-S or one of its metabolites significantly interferes in the testosterone assay when at higher concentrations.

Adult↗
PubMed2003

Analytical and clinical aspects of adrenocorticotrophin determination.

Adrenocorticotrophin (ACTH) is formed from the cleavage of pro-opiomelanocortin. Measurement of plasma ACTH is a key step in the differential diagnosis of hypothalamic-pituitary-adrenal disorders. Prior to the development of radioimmunoassay, the bioassays employed for the determination of ACTH were highly complex, time-consuming and costly in terms of number of animals used. Their sensitivity was such that the normal early morning peak of ACTH could not be determined. The introduction of immunoassay methodology enabled the measurement of low normal ACTH concentrations. Immunological recognition of ACTH by the antibodies employed offered improvements with regard to specificity. The development of two-site immunometric assays further improved specificity and the ability to measure low normal ACTH concentrations without the need to extract large volumes of plasma. The quantification of ACTH is now routinely performed in clinical laboratories, with non-radioisotopic methods becoming increasingly popular. ACTH measurement is of limited value in distinguishing between the causes of Cushing's syndrome, as there is considerable overlap in circulating ACTH concentrations in subjects with either a pituitary or an ectopic tumour. The role of ACTH precursor and related peptides in normal and pathological states and the clinical utility of their measurement remain to be fully elucidated. However, there is evidence that measurement of ACTH precursors can be a useful diagnostic tool in identifying the aetiology of Cushing's syndrome. This review will primarily address methodological aspects of ACTH measurement in the diagnosis of clinical conditions.

Adrenocorticotropic Hormone↗
PubMed2000

The development of a sialic acid specific lectin-immunoassay for the measurement of human chorionic gonadotrophin glycoforms in serum and its application in normal and Down's syndrome pregnancies.

OBJECTIVE: We have developed and validated a lectin-immunoassay for the recognition of sialic acid residues on hCG glycoforms in serum. DESIGN: This assay employs a hCG specific capture antibody and a sialic acid specific lectin (Wheat Germ Agglutinin) labelled with horse radish peroxidase. RESULTS: The standard curve covered hCG concentrations of 0-4000 IU/l (3rd IS for hCG, 75/537) with an analytical sensitivity of 1.0 IU/l. The within and between batch coefficient of variation was < 7% for all doses. Cross-reactivity of < 1% with TSH, LH, FSH, hCGalpha, hCGbeta and desialylated hCG confirmed assay specificity. Dilutions of serum of < 10% final concentration were parallel to the standard curve (within and between batch CV, < 6%). The assay working range was 100 - > 500 000 IU/l and the recovery of hCG from serum was in the range of 94.5% to 115.4%, with a mean value of 102.1%. The assay detected a time dependent change in hCG sialylation during normal pregnancy with the relative abundance of sialylated hCG declining after week 9 and increasing after week 15 of gestation. In addition preliminary studies showed that maternal serum hCG concentrations measured with the lectin-immunoassay were elevated in high risk Down's pregnancies (as defined by conventional screening tests between weeks 16-18 gestation, median multiple of median, 3.14; range 1.81-19.12, P < 0. 001) and low risk (1.57, 0.49-6.14, P = 0.034) compared to normal (1. 00, 0.32-3.20) pregnancies. Furthermore, the lectin immunoassay had greater discriminatory power compared to conventional immunoassay of hCG and hCGbeta between normal and both low and high risk Down's pregnancies. CONCLUSION: This assay will allow analysis of serum samples for the investigation of sialylated variants of hCG glycoforms in various pathological and physiological situations.

Analysis of Variance↗
PubMed2000

Inhaled nitric oxide reduces the need for extracorporeal membrane oxygenation in infants with persistent pulmonary hypertension of the newborn.

OBJECTIVE: We previously reported improved oxygenation, but no change, in rates of extracorporeal membrane oxygenation (ECMO) use or death among infants with persistent pulmonary hypertension of the newborn who received inhaled nitric oxide (NO) with conventional ventilation, irrespective of lung disease. The goal of our study was to determine whether treatment with inhaled NO improves oxygenation and clinical outcomes in infants with persistent pulmonary hypertension of the newborn and associated lung disease who are ventilated with high-frequency oscillatory ventilation (HFOV). DESIGN: Single-center, prospective, randomized, controlled trial. SETTING: Newborn intensive care unit of a tertiary care teaching hospital. PATIENTS: We studied infants with a gestational age of > or =34 wks who were receiving mechanical ventilatory support and had echocardiographic and clinical evidence of pulmonary hypertension and hypoxemia (PaO2 < or =100 mm Hg on FIO2 = 1.0), despite optimal medical management Infants with congenital heart disease, diaphragmatic hernia, or other major anomalies were excluded. INTERVENTIONS: The treatment group received inhaled NO, whereas the control group did not. Adjunct therapies and ECMO criteria were the same in the two groups of patients. Investigators and clinicians were not masked as to treatment assignment, and no crossover of patients was permitted. MEASUREMENTS AND MAIN RESULTS: Primary outcome variables were mortality and use of ECMO. Secondary outcomes included change in oxygenation and duration of mechanical ventilatory support and supplemental oxygen therapy. Forty-two patients were enrolled. Baseline oxygenation and clinical characteristics were similar in the two groups of patients. Infants in the inhaled NO group (n = 21) had improved measures of oxygenation at 15 mins and 1 hr after enrollment compared with infants in the control group (n = 20). Fewer infants in the inhaled NO group compared with the control group were treated with ECMO (14% vs. 55%, respectively; p = .007). Mortality did not differ with treatment assignment. CONCLUSIONS: Among infants ventilated by HFOV, those receiving inhaled NO had a reduced need for ECMO. We speculate that HFOV enhances the effectiveness of inhaled NO treatment in infants with persistent pulmonary hypertension of the newborn and associated lung disease.

Administration, Inhalation↗
PubMed1999

Macroprolactinaemia: validation and application of the polyethylene glycol precipitation test and clinical characterization of the condition.

OBJECTIVE: The clinical characteristics and natural history of macroprolactinaemia are yet to be fully established and there is currently no widely accepted simple in vitro test for routine identification of the condition. This study was designed to further validate the polyethylene glycol (PEG) precipitation test with assessment of percentage prolactin recovery (%R), for the detection of macroprolactinaemia and clinically characterize cases identified using the test. DESIGN: Analytical validation and application of the PEG precipitation test for diagnosis of macroprolactinaemia and a retrospective case-notes review of some of the patients identified with the condition. PATIENTS: Sera from 188 patients with elevated serum prolactin (PRL) concentrations were screened for macroprolactinaemia. Seventeen of the patients who were under follow-up at the local teaching hospital and were identified to have macroprolactinaemia were systematically characterized clinically. MEASUREMENTS: Prolactin was measured in sera, fractions from gel filtration chromatography and supernatant obtained after PEG precipitation, by the DELFIA fluoroimmunoassay. CLINICAL ENDPOINTS: Initial serum PRL and symptoms and their response to dopamine agonist therapy; imaging of the pituitary gland; serum PRL and symptoms after cessation of dopamine agonist therapy; course of serum PRL and symptoms without dopamine agonist therapy. RESULTS: The within-batch coefficient of variation (CV) of the PEG precipitation test ranged between 2.8 and 7.3% while the between-batch CV ranged between 3.4 and 9.7%. Intra-individual variability up to five months was 9.9%. A prolactin recovery </= 40% was indicative of macroprolactinaemia, while the condition was unlikely to be present at values > 50%. The prevalence of macroprolactinaemia was 15% without sex difference. Clinical characterization of 17 patients showed modest initial serum PRL concentrations and there was imaging evidence of a coexisting pituitary adenoma in three of them. Dopamine agonist therapy resulted in substantial falls in serum PRL and this was associated with improvement or resolution of symptoms in some patients. Stoppage of dopamine agonist resulted in rebound hyperprolactinaemia in all cases. Spontaneous improvement in symptoms occurred in three patients but hyperprolactinaemia persisted in all those who were not on treatment. CONCLUSIONS: The PEG precipitation test with assessment of 'free' prolactin has been shown to be reproducible and sensitive for the detection of macroprolactinaemia. Many of the patients who had macroprolactinaemia presented with at least one symptom of the hyperprolactinaemic syndrome. Dopaminergic therapy may influence the course of both serum PRL and symptoms in some of these patients.

Adolescent↗
PubMed1999

Do immunoassays differentially detect different acidity glycoforms of FSH?

OBJECTIVE: The possibility of the carbohydrate residues of glycoproteins affecting their recognition in immunoassays is an important and unresolved issue. This study looked for evidence of differential recognition of FSH glycoform preparations, of variable isoelectric point (pI) and known molarity, using three routine assays employing different antibody configurations. DESIGN: Seven glycoform preparations with differing pI bands (between 3.8 and 5.5) were produced by isoelectric focusing of recombinant human FSH and the molecular weights determined by mass spectroscopy. Three concentrations of each glycoform were assayed and the results expressed relative to unfractionated material. From the relative responses, recognition differences between the assay methods and between the glycoform preparations were investigated. MEASUREMENTS: Three routine assays were employed: the commercially available Amerlite(R) enzyme immunoassay and Delfia(R) immunofluorometric assay, together with an in-house competitive two-site radioimmunoassay (RIA). RESULTS: Overall, the three assays gave the same relative responses for equivalent glycoforms, with the only exceptions involving small differences between some assay pairs for the fractions at the extremes of the pI range investigated. Within each assay type, differences (P < 0.05) of up to 33% existed between glycoforms of different pI, however, these differences showed no patterns or trends across the entire acidity range examined. CONCLUSIONS: Between the assay methods investigated in this study, few differences exist in the recognition of individual pI bands of FSH when expressed relative to a common unfractionated standard. Differences were apparent in the recognition of the different acidity glycoforms within each assay method, however, these were small and unlikely to be of clinical significance.

Analysis of Variance↗
PubMed1999

Three cases of macroprolactinaemia.

A woman with hirsutism but otherwise symptom-free was found to have a raised serum prolactin and a pituitary microadenoma. The hyperprolactinaemia persisted despite bromocriptine therapy and subsequent pituitary surgery, which yielded a non-functioning adenoma. After a further 15 years with persistent hyperprolactinaemia but no symptoms, macroprolactinaemia was diagnosed. Such cases might account for part of the failure rate of pituitary microsurgery for prolactinoma. Testing for macroprolactinaemia is advisable in a woman with hyperprolactinaemia, especially if her ovulatory cycle is normal. Two other cases are reported in which macroprolactinaemia was associated with menstrual disturbances and other hormonal effects: in these, treatment with dopamine agonists suppressed the hyperprolactinaemia and restored normal menstrual cycles.

Adult↗
PubMed1998

Surface plasmon resonance: a study of the effect of biotinylation on the selection of antibodies for use in immunoassays.

Surface plasmon resonance is a valuable optical phenomenon for monitoring biomolecular interactions in real time. In this project anti-mouse-Fc was coupled to the carboxymethyl dextran coating on the surface of a CM5 sensor chip (BIAcore) using amine coupling. Monoclonal antibodies (MAbs) to Luteinizing Hormone (LH) were then captured on this surface in the correct orientation for binding. LH (500 IU/l) was injected over the surface and the subsequent binding and dissociation events were monitored. The resulting optical response curves allowed fast analysis of the binding interactions of eight selected MAbs. It was possible to develop a two-site immunometric assay for LH using a pair of these MAbs. The effect of biotinylating the MAbs, using various biotin:antibody coupling ratios, on their subsequent binding to both LH and avidin conjugated alkaline phosphatase was also investigated. This approach has allowed rapid evaluation of the effect of changes in both reagent and reaction conditions on immunoassay performance and appears to be a valuable adjunct to immunosensor and immunoassay development.

Alkaline Phosphatase↗
PubMed1997

Effect of inhaled nitric oxide on endothelin-1 and cyclic guanosine 5'-monophosphate plasma concentrations in newborn infants with persistent pulmonary hypertension.

OBJECTIVE: To examine the role of endogenous nitric oxide (NO) and endothelin-1 (ET-1) in the pathogenesis of persistent pulmonary hypertension of the newborn (PPHN) and to determine whether inhaled NO, currently under investigation as a new therapy for PPHN, affects plasma concentrations of these vasoactive mediators. METHODS: Circulating ET-1 and cyclic guanosine monophosphate (cGMP) concentrations were measured by radioimmunoassay in 15 healthy term newborn infants and 46 newborn infants with PPHN enrolled in a randomized, controlled trial of inhaled NO. These concentrations were followed up longitudinally and compared between the NO and the conventionally treated group. RESULTS: Concentrations of ET-1 were significantly higher and cGMP concentrations significantly lower in infants with PPHN compared with healthy newborn infants (median ET-1, 28 vs 11 pmol/L; p = 0.0001; median cGMP, 35 vs 61 pmol/ml; p = 0.0001, respectively). ET-1 concentrations showed an upward trend at 1 and 24 hours of treatment and a subsequent decline at recovery in both subgroups of patients, with the most pronounced decrease in the NO group. cGMP concentrations increased significantly only in the NO group, with a peak at 1 hour of treatment (median, 61 pmol/ml). As the dose of NO decreased, cGMP concentrations declined. In contrast, conventionally treated infants manifested no change in cGMP concentrations from baseline until recovery, when a significant decrease was noted (median decrease of 13 pmol/ml; p = 0.002). We did not find a significant difference between ET-1 and cGMP concentrations in infants who required extracorporeal membrane oxygenation compared with those who did not. CONCLUSIONS: PPHN is associated with increased ET-1 and decreased cGMP plasma concentrations, which may contribute to the pathogenesis of the disease. Inhaled NO appears to modulate these mediators during the disease process, suggesting an interaction between ET-1 and NO in vivo.

Administration, Inhalation↗
PubMed1997

Improved oxygenation in a randomized trial of inhaled nitric oxide for persistent pulmonary hypertension of the newborn.

OBJECTIVE: To determine the effect of inhaled nitric oxide (NO) on clinical outcome in newborns with persistent pulmonary hypertension (PPHN). DESIGN: A prospective, randomized trial of patients referred to a level 3 nursery in a single large center. Clinicians were not masked to group assignment. Crossover of patients from control to NO treatment was not permitted. METHODS: We randomized 49 mechanically ventilated newborns, transferred to our center with clinical and echocardiographic evidence of severe PPHN (arterial oxygen tension [PaO2] <100; fractional inspired oxygen = 1) to treatment with or without NO. Patients with gestational age <34 weeks or with congenital heart disease or diaphragmatic hernia were excluded. High-frequency oscillatory ventilation was used but not allowed concomitantly with NO. Primary outcome variables were oxygenation, mortality, and use of extracorporeal membrane oxygenation (ECMO). RESULTS: Meconium aspiration syndrome and isolated PPHN were the most common diagnoses (32/49) and were distributed equally between groups. The median age at the time of entry into the study was similar between groups, 25 hours for control patients and 18 hours for NO patients. Median baseline oxygenation index (OI) was similar in 23 control (OI = 29) and 26 NO (OI = 30) patients. Mortality (8%), use of ECMO (33%), median days on mechanical ventilation (9 days), and duration of supplemental oxygen (13 days) were not different between treatment groups. PaO2, oxygen saturation, and OI improved in the NO group compared with baseline and to control patients at 15 minutes. The median percent change in OI (-31%) in the NO group was significantly different from baseline and from the control group. The difference in oxygenation between treatment groups was still apparent 12 hours after baseline. Before cannulation for ECMO, oxygenation was better in the NO group compared with control patients. Among patients who were placed on ECMO, the median time from baseline to ECMO cannulation was 2.4 hours (range, 1 to 12 hours) among control patients and 3.3 hours (range, 2 to 68 hours) for those randomized to receive NO. There was a tendency to observe fewer adverse neurologic events (seizure and intracranial hemorrhage) in the NO group (4/26 vs 8/23). One child with alveolar capillary dysplasia confirmed by postmortem examination could not be weaned from 80 parts per million of NO and transiently developed methemoglobinemia (peak methemoglobin level = 17%). No other side effects were observed. CONCLUSIONS: Although mortality and ECMO use were similar for both treatment groups using this study size and design, sustained improvement in oxygenation with NO and better oxygenation at initiation of ECMO may have important clinical benefits. We speculate that modification of treatment to include specific lung expansion strategies with NO treatment and recognition that early improvement of oxygenation may be sustained with NO may lead to reduced use of ECMO in NO treated patients compared with controls.

Administration, Inhalation↗
PubMed1992

Method comparison--a different approach.

The commonly accepted method of analysing data from method comparison studies is regression analysis, a method which has limitations. This study illustrates the use of a graphical presentation of data, the difference plot, which can be used as an alternative to least squares regression analysis. The data from comparison studies performed on five methods were analysed both by Deming's regression analysis, with calculation of the correlation coefficient, and by the difference plot. The results show that in most cases much more relevant information was obtained from the difference plot.

Androstenedione↗
PubMed1986

A method for the identification of apolipoprotein E isoforms employing chemical precipitation and flat bed isoelectric focusing in agarose.

A method is described for the identification of apolipoprotein E phenotypes. Lipoproteins were precipitated by magnesium chloride/phosphotungstate reagent and isoelectric focusing performed on flat-bed agarose. Sensitivity was enhanced by blotting with nitrocellulose prior to staining. The system described requires no ultracentrifugation step and allows up to 20 samples to be processed in each run. Agarose has some advantages over the more commonly used polyacrylamide gels for isoelectric focusing.

Apolipoproteins E↗
PubMed1979

Difference between end-tidal and arterial PCO2 in exercise.

The relation between end-tidal carbon dioxide tension (PETCO2) measured by infrared analysis and arterial carbon dioxide tension (PaCO2) during exercise was systematically examined in five healthy adults at two power outputs (25 and 50% VO2max) and at three frequencies of breathing (15, 30, and 45 breaths/min). PETCO2-PaCO2 varied between -2.5 and +9.1 Torr, was inversely related to the frequency of breathing (r = 0.475), and directly related to tidal volume (VT; r = 0.791) and CO2 output (r = 0.627). An equation was obtained by multiple regression analysis, to predict PaCO2 from PETCO2: PaCO2 = 5.5 +0.90 PETCO2 -0.0021 VT (r = 0.915). The equation was applied to measurements of PETCO2 obtained in two previous studies in 10 subjects in which PaCO2 had been measured, and was found to predict PaCO2 to within 1.04 Torr (+/- SD) for PaCO2 between 25 and 58 Torr (n = 56; r = 0.962). The effect of the response characteristics of the CO2 analyzer on the measurement of PETCO2 was also systematically examined by comparison with a fast-responding respiratory mass spectrometer.

Adult↗
PubMed1979

Use of sodium salicylate as a blocking agent for cortisol-binding-globulin in a radioimmunoassay for cortisol on unextracted plasma.

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

Anilino Naphthalenesulfonates↗
PubMed1975

Determination of hemoglobin-oxygen affinity on micro samples.

The spectrophotometric determination of hemoglobin-oxygen dissociation on dilute red cell suspensions has been modified by the use of a bicarbonate buffer containing bovine serum albumin. The red cell suspension is equillibrated with known ratios of air and nitrogen and 5 per cent carbon dioxide at atmospheric pressure using two gas pumps. The method enables the hemoglobin-oxygen dissociation curve to be measured on 10 to 20 mul of whole blood, and has given values for the P50 (the oxygen tension at 50 per cent hemoglobin-oxygen saturation) of 25.9 plus or minus 1.5 S. D. which are comparable to the value of 26.0 plus or minus 1.0 S. D. obtained by the mixing technique and by other methods. The addition of bovine albumin (35 mg. per cent or greater) increased the P50 by 3 mm. Hg above that obtained with buffer alone. The P50 value has been compared in bis-Tris and phosphate buffers with and without albumin, and in bicarbonate buffers with the addition of approximately equimolar concentrations of either human or bovine serum albumin or polyvinyl-pyrrolidone (PVP), and buffer alone. The effect of albumin on the P50 value was most marked in bicarbonate buffer, and was statistically significantly greater in the presence of human or bovine albumin than in buffer alone or buffer plus PVP. The addition of albumin could not be explained through an alteration of cell shape or volume, but may be an influence on intracellular pH.

Adenosine Triphosphate↗