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Biomedical subjects

I Gibb

Publications and source records attributed to I Gibb.

At least 19 recordsLinked to original sources
PubMed1999

Multicenter evaluation of Tosoh glycohemoglobin analyzer.

BACKGROUND: We describe an Anglo-French evaluation of a new analyzer. METHODS: The Tosoh HLC-723 GHb V, A1c2.2 glycohemoglobin analyzer is an HPLC instrument with primary blood tube sampling, bar-code reading, cap piercing, and the ability to chromatographically separate labile hemoglobin A1c (HbA1c). We evaluated two analytical protocols, 2.2 and 3.0 min, and compared results for blood samples collected from diabetic and nondiabetic subjects with those obtained with Bio-Rad Diamat and Variant analyzers. RESULTS: Within- and between batch-imprecision (CVs) was <2% with linearity to at least 15.9% HbA1c. Although some hemoglobinopathies were detected in the 2. 2-min chromatography, clearer evidence of abnormality was visible in the 3.0-min version. Comparison with established methods showed good correlation (r = 0.993; n = 316 with Diamat; and r = 0.995; n = 133 with Variant) but highlighted calibration differences. CONCLUSIONS: The problems of manual blood sample preparation, labile HbA1c, and carbamylated hemoglobin interference associated with the older instruments have been eliminated in the new Tosoh analyzer. The 3. 0-min protocol is preferred for routine use.

Adult↗
PubMed1997

Standardization of glycated haemoglobin assays throughout the Northern region of England: a pilot study.

We describe a pilot study designed to assess the comparability of measurements of glycated haemoglobin among 15 laboratories in the North of England. We also evaluated a means of improving agreement and aligning results by referencing locally measured values to those obtained by the central biochemistry laboratory of the Diabetes Control and Complications Trial research group. Blood samples from 50 diabetic and non-diabetic subjects were analysed for glycated haemoglobin content in the participating and reference laboratories using a variety of routinely available methods. The mean CV for these results was 15.3% (95% confidence interval 14.0% to 16.5%). Using a regression equation relating a subset of seven of these results to their assigned reference values, a glycated haemoglobin index was calculated for all the other samples distributed. The mean inter-laboratory CV improved to 4.6% (95% confidence interval 4.0% to 5.1%), p<0.0001. The percentage bias of results from the reference method also improved from 15.1% (95% confidence interval 9.4 to 20.1) to 4.67% (95% confidence interval 4.05 to 5.25) after alignment, p<0.001. This study demonstrated that substantial method related differences between reported glycated haemoglobin results exist. These can be reduced using a simple calibration strategy in which data are correlated to an established method with associated extensive clinical interpretive value as established by the DCCT.

Analysis of Variance↗
PubMed1997

Effect of insulin on systemic and renal handling of albumin in nondiabetic and NIDDM subjects.

Insulin resistance and hyperinsulinemia cluster with microalbuminuria in both diabetic and nondiabetic subjects, but the mechanism underlying this association is unknown. To test the hypothesis that insulin influences protein permeability, we measured the albumin transcapillary escape rate (TER) by the (131)I-labeled albumin technique in 12 healthy volunteers and 12 normoalbuminuric NIDDM patients (fasting plasma glucose, 10.9 +/- 1.3 mmol/l) during 4 h of isoglycemia with high (1.1 mU x min(-1) x kg(-1)) or, on a different day, low (0.1 mU x min(-1) x kg(-1)) insulin infusion. In both patients and control subjects, high insulin was associated with a 7% decrease in blood volume (P = 0.006) and a 6% decrease in diastolic blood pressure (P < 0.02), these two changes being related to one another (r = 0.56, P < 0.01). Basal albumin TER was similar in patients (8.4 +/- 0.5% x h(-1)) and control subjects (7.7 +/- 0.7% x h(-1)) and was not significantly changed by high insulin in either group (patients vs. control subjects, 7.3 +/- 0.9 vs. 6.2 +/- 0.4% x h(-1); NS vs. low insulin). In contrast, high insulin increased renal albumin excretion (from 3.6 +/- 0.8 to 5.4 +/- 1.1 microg/min, P < 0.01) and clearance rate (0.09 +/- 0.02 to 0.13 +/- 0.03 microl/min, P < 0.001) in patients but not in control subjects. To localize the effect of insulin along the nephron, we measured the urinary excretion of N-acetyl-beta-D-glucosaminidase (beta-NAG), released by the proximal tubule; retinol-binding protein (RBP), reabsorbed by the proximal tubule; and Tamm-Horsfall protein (THP) and epidermal growth factor (EGF), both secreted by the distal tubule. For both beta-NAG and RBP, but not EGF or THP, insulin enhanced urinary excretion (diabetics vs. controls: beta-NAG, 0.48 vs. -0.15 microU/min [P = 0.03]; RBP, 78 vs. -32 ng/min [P = 0.05]). In conclusion, physiological hyperinsulinemia does not affect systemic albumin permeability in healthy subjects or normoalbuminuric NIDDM patients. In contrast, in NIDDM patients, but not in healthy subjects, insulin increases the urinary excretion of albumin and protein markers of proximal tubular function. The significance of this finding for the pathogenesis of diabetic nephropathy remains to be established.

Adult↗
PubMed1996

Measures of tubular function in normoalbuminuric insulin-dependent diabetic patients and their relationship with sodium lithium countertransport activity.

The aim of this study was to assess the relationship between markers of tubular function, markers of glycaemic control and erythrocyte sodium-lithium countertransport activity (SLC) in 40 normotensive, normoalbuminuric insulin-dependent diabetic (IDDM) subjects and 11 normal control subjects. Nine IDDM subjects had SLC > 0.40 mmol lithium h-1 litre RBC-1. Glomerular filtration rate (GFR) and the excretion rate of retinol-binding protein (RBP), N-acetyl-beta-D-glucosaminidase (beta-NAG) and glucose were significantly higher in IDDM subjects compared to control subjects (Mann-Whitney test, p = 0.02, < 0.001, < 0.001 and < 0.001, respectively), whilst the two groups had similar SLC and TmPO4 levels. There was no significant relationship between SLC and the other variables in IDDM subjects, even when comparing IDDM subjects with normal and high SLC. beta-NAG excretion rate was correlated to urinary glucose (rs 0.47, p = 0.001) and, weakly, to the other markers of glycaemic control (fasting blood glucose rs = 0.31, p = 0.03, fructosamine rs 0.28, p = 0.04, HbA1 rs 0.27, p = 0.04). RBP excretion rate was correlated to the excretion rate of beta-NAG (rs 0.38; p = 0.007) and albumin (rs 0.45; p = 0.002); the excretion rates of beta-NAG and albumin were significantly associated (rs 0.37, p = 0.009). Diabetes duration did not correlate to any of the aforementioned variables. In this study, beta-NAG and RBP overnight excretion rates were higher in normoalbuminuric IDDM subjects compared to control subjects but no relationship was present between SLC and tubular function in IDDM patients without complications. Excretion rates of different proteins appear to be interrelated and, in IDDM, beta-NAG excretion is associated with glycaemic control.

Adolescent↗
PubMed1993

Effect of posture and acute glycaemic control on the excretion of retinol-binding protein in normoalbuminuric insulin-dependent diabetic patients.

1. It has been suggested that tubular damage may precede glomerular damage at the onset of diabetic nephropathy. This may be reflected by increased urinary excretion of low-molecular-mass proteins, such as retinol-binding protein. 2. We have measured the urinary excretion rate of retinol-binding protein overnight, during orthostasis and during a hyperinsulinaemic euglycaemic clamp (blood glucose concentration 7.0 mmol/l) with stable diuresis in 34 normotensive, normoalbuminuric insulin-dependent diabetic patients and in 10 normal control subjects. Normal control subjects were not clamped. A further four normoalbuminuric insulin-dependent diabetic patients were rendered euglycaemic without a water load. 3. Overnight retinol-binding protein excretion rate was 58 (16-157) [median(range)] ng/min in patients with insulin-dependent diabetes and 32 (15-72) ng/min in control subjects (P < 0.01). The excretion rate did not change during orthostasis [patients with insulin-dependent diabetes, 67 (3-173) ng/min; control subjects, 23 (5-78) ng/min]. During the euglycaemic clamp retinol-binding protein excretion rate increased to 383 (78-4897) ng/min in patients with insulin-dependent diabetes (P < 0.01). An average increment in retinol-binding protein excretion rate of greater than 4000% was noted after acute euglycaemia in those patients with insulin-dependent diabetes who were not water-loaded. 4. In insulin-dependent diabetes, both overnight and orthostatic retinal-binding protein excretion was not correlated with fasting blood glucose concentration, HbA1, fructosamine or duration of diabetes. The absolute and incremental excretion rates of retinol-binding protein during the clamp were, however, correlated with both fasting blood glucose concentration and glucose excretion rate (rs = 0.41-0.48, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

HemoCue: evaluation of a portable photometric system for determining glucose in whole blood.

We assessed the HemoCue system for measuring glucose in 5 microL of whole blood. A glucose dehydrogenase-based reaction is used with dried reagents contained in disposable microcuvettes, which are filled with blood by capillary action. Automated hexokinase and YSI 23AM glucose analyzer methods were used for comparison. Overall imprecision (CV) was better than 4.5%, with no significant differences in results between three different HemoCue photometers and four batches of microcuvettes. Regression slopes (+/- SE) were 0.947 (0.011) with the YSI and 0.966 (0.015) with the hexokinase method. Analytical recovery of added glucose was 101-106%, and the system functioned with hematocrits up to 0.65. Bilirubin up to 453 mumol/L did not interfere, but high concentrations of endogenous (greater than 3 mmol/L) and exogenous triglycerides gave positive interference. The system proved stable and robust under a wide range of storage and handling conditions; performance was impaired only at high ambient temperature (37 degrees C). We conclude that the HemoCue system should prove useful for glucose measurement; further testing outside the laboratory is warranted.

Bilirubin↗
PubMed1991

Assessment of chemotherapy-associated nephrotoxicity in children with cancer.

Assessment of the toxicity caused by chemotherapy in children with cancer has become more important as the number of long-term survivors has continued to increase. It is vital to monitor both acute life-threatening adverse effects and long-term toxicity that may impair the child's development and cause permanent morbidity. Renal damage may follow treatment with cytotoxic drugs, especially cisplatin or ifosfamide, and lead to glomerular, proximal tubular or distal tubular impairment or to any combination of these. Greater understanding of nephrotoxicity and of its prevention may enable the use of more intensive schedules or of higher doses of potentially nephrotoxic chemotherapy. However, the evaluation of cytotoxic drug-induced nephrotoxicity has frequently depended mainly on measurement of the plasma creatinine concentration, which may remain normal despite substantial glomerular impairment or severe tubular dysfunction. Detailed assessment of nephrotoxicity depends on an understanding of normal renal physiology and requires evaluation of all aspects of function. A comprehensive but simple investigatory protocol that enables assessment of the nature and severity of nephrotoxicity in children is described, which can be performed without admission to hospital. Glomerular function is assessed by measurement of the glomerular filtration rate from the plasma clearance of [51Cr]-ethylenediaminetetraacetic acid ([51Cr]-EDTA). Proximal nephron function is evaluated in three ways: by measurement of the concentration of calcium, magnesium, phosphate, glucose and urate in blood and urine along with calculations of their fractional excretion and of the renal threshold for phosphate; by determination of the excretion in urine of low-molecular-weight proteins (e.g. retinol-binding protein); and by investigation of urinary bicarbonate excretion in patients who are acidotic. Distal nephron function is initially investigated by examination of the concentration (osmolality) and acidification (pH) of an early morning sample of urine. Finally, a group of general investigations is performed, including quantitation of urinary excretion of renal tubular enzymes (e.g. N-acetylglucosaminidase) and measurement of blood pressure.

Acid-Base Equilibrium↗
PubMed1988

Immunologically measured serum markers and their role in the management of prostate cancer.

Serum prostatic acid phosphatase and prostate-specific antigen have been measured in a group of 106 cases of newly diagnosed prostate cancer. The serum levels of the tumour markers have been correlated with the clinical and ultrasound staging of the prostate cancer at diagnosis. All patients were managed by a deferred treatment policy. Patients without detectable metastases at presentation have been assessed after a period of 2 years to determine if the level of serum tumour markers at diagnosis could predict subsequent disease progression. The study has demonstrated that a combination of immunologically measured acid phosphatase and prostate-specific antigen is the best method of assessing the prognosis of an individual prostate cancer at the time of presentation.

Acid Phosphatase↗
PubMed1987

Evaluation and assessment of new disposable strip for determination of plasma potassium concentration.

Overall laboratory reproducibility for the Ames Seralyzer and plasma potassium test strips was less than 4% within the plasma reference range; and linearity extended from 2.1 to 10.2 mmol/l. Neither bilirubin nor lipaemia interfered in the analysis and selectivity for potassium over sodium was 450:1. Laboratory comparison with automated flame photometry and an indirect ion selective electrode showed a Seralyzer bias of +0.10 (+/- 25D 0.26) and +0.11 (0.27) mmol/l. Against flame photometry, comparison of analyses by six doctors from a coronary care unit and four nurses from a renal dialysis unit showed smaller positive biases (0.06 and 0.02 mmol/l) but substantially larger error ranges (0.43 and 0.55 mmol/l, respectively). Some 49% of the nurses' and 37% of the doctors' results differed from laboratory values by more than 0.2 mmol/l. Potassium test strip results proved acceptably comparable and reproducible when produced by an experienced analyst, but greater variability in clinical hands rendered the system unsuitable for precise monitoring of potassium concentration.

Humans↗
PubMed1986

Use and misuse of a digoxin assay service.

In a study of the use of a digoxin assay service and its influence on clinical management 285 assay requests were audited over 12 weeks. For 67 (24%) there was no clear clinical indication for the request and for 140 the period between the last dose of digoxin being given and the blood sample being taken was either unknown or inappropriate. Treatment in 64 patients (22%) was changed after the assay result was received [corrected]. 24 of these changes bore no relation to the original clinical indication for requesting the assay, suggesting that such changes were based on the assay result alone. Of samples collected within six hours after the last dose, 15 of 69 (22%) led to a reduction in treatment compared with 10 of 116 (9%) taken after six hours (p less than 0.025), thereby highlighting the danger that incorrectly timed samples may lead to inappropriate clinical decisions.

Clinical Laboratory Techniques↗
PubMed1986

Immunological and colorimetric determination of prostatic acid phosphatase--technical and clinical reappraisal in symptomatic patients.

We compared a selection of quantitative immunological methods for prostatic acid phosphatase (PAP) with routine colorimetric assays for total and tartrate-labile acid phosphatase and evaluated their relative clinical merits in the differential diagnosis of prostatic carcinoma. We also assessed a wide range of commercial control materials for suitability of use with these methods. Patients studied included 111 cases of prostatic carcinoma, 42 cases of benign prostatic hyperplasia, and 33 controls. The principles of the methods used included determination of enzymatic activity using p-nitrophenyl phosphate, RIA, immunoradiometric, and enzymoimmunometric assays. Performance characteristics for the immunological methods were inferior to manufacturers' precision and specificity claims. We identified control materials that were unsuitable for routine use. Poor discrimination between clinical groups was observed for all methods. Analysis by use of a receiver operator characteristic plot failed to improve this. We conclude that the immunological methods we studied offer no advantages over colorimetric methods in the differential diagnosis of prostatic cancer in symptomatic patients.

Acid Phosphatase↗
PubMed1985

Rapid measurement of creatine kinase activity in a coronary care unit using a portable benchtop reflectance photometer.

Rapid measurements of plasma creatine kinase activity using an inexpensive benchtop reflectance photometer (Ames Seralyzer) and disposable reagent strips were evaluated in the laboratory and coronary care unit. The system proved simple to use and capable of yielding rapid (four minutes per analysis), precise (coefficient of variation less than 9%), and accurate results (correlation with routine method 0.995) when used by medical staff. Creatine kinase values were available 6.5-102 hours earlier than routine laboratory data, depending on the time and day of sampling, thereby facilitating appropriate and economic patient management. This instrument might be used to supplement the routine enzyme service for selected admissions, resulting in greatly improved availability of results and hence contributing to the early discharge of patients from intensive care facilities.

Clinical Enzyme Tests↗
PubMed1985

Rapid ward assessment of renal function by reflectance photometric determination of plasma creatinine.

The Ames Seralyzer reflectance photometer and disposable reagent strips for the determination of plasma creatinine were evaluated in the laboratory and on a urology ward over a 3-month period. Principles of the instrument used are described, as are details of the evaluation procedures. Reproducibility of results under optimum conditions gave coefficients of variation less than 7%. Under routine conditions of use, medical staff and laboratory analysts achieved high correlation with the routine laboratory method of analysis (r = 0.986, N = 108: r = 0.996, N = 102 respectively). Potential sources of inaccuracy were identified. Seralyzer determination of plasma creatinine can be rapidly, simply and reliably performed by medical staff on a urology ward, thereby facilitating assessment of renal function governed by clinical requirement rather than by laboratory convenience.

Creatinine↗