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Biomedical subjects

C G Fraser

Publications and source records attributed to C G Fraser.

At least 37 records · Page 2Linked to original sources
PubMed1996

Characterization and classification of external quality assessment schemes (EQA) according to objectives such as evaluation of method and participant bias and standard deviation. External Quality Assessment (EQA) Working Group A on Analytical Goals in Laboratory Medicine.

Within the scope of this paper, the Working Group has attempted to place external quality assessment (EQA) within the whole context of quality management in laboratory medicine. First, the objectives of EQA schemes are defined and current EQA schemes evaluated. In most schemes, the objectives are not defined a priori and do not allow the definition of the origin of unacceptable individual results from participants. There is an ongoing trend for making traditional EQA schemes more interesting for the participants. Analysis of the factors involved in analytical quality allow the definition of the essential analytical tasks of educational EQA schemes. Beside these quality control tasks, educational EQA also includes quality assurance elements. EQA today has not only an important role to play in the assessment of each participant's performance but also in the assessment of the method. Efficiency of the schemes and educational impact can be improved by appropriate scheme designs according to objectives. After this theoretical approach, some practical examples of problem related EQA designs are given.

Clinical Laboratory Techniques↗
PubMed1995

Desirable performance standards for imprecision and bias in alternate sites. The views of laboratory professionals.

Many strategies exist for the delineation of desirable performance standards for imprecision and inaccuracy (bias). All have disadvantages and advantages. Currently, the professional consensus is that the favored approach is based on biology: desirable imprecision is less than one half of the within-subject biological variation and desirable inaccuracy is less than one quarter of the group (within-subject plus between-subject) biological variation. Current laboratory performance allows these goals to be met for many quantities. In the past, analyses done at sites other than the laboratory achieved poorer results, but recent advances in technology appear to allow some biology-based goals, which in our view are the appropriate standards, to be met. Further advances in setting and widely promulgating goals, making good calibrants widely available, and developing quality control, assessment, and management are all required to ensure that the desirable performance standards are obtained in all locations in the future.

Attitude of Health Personnel↗
PubMed1995

Desirable routine analytical goals for quantities assayed in serum. Discussion paper from the members of the external quality assessment (EQA) Working Group A on analytical goals in laboratory medicine.

The aim of the Working Group was to describe guidelines for deriving desirable analytical goals in laboratory medicine. First, a literature review is given of the different approaches used until now, and some of the most important studies are presented in detail. These approaches are then discussed critically, and the analytical goals proposed by the group are outlined with respect to monitoring and diagnostic testing. The group recommends that, most realistically, analytical quality specifications be biologically based. For diagnostic testing, the aim is achievement of accuracy, allowing the use of common reference intervals when populations are homogeneous for a given quantity. For monitoring (within an individual laboratory and performed with the same instrument), analytical performance should aim at stable operation and low imprecision compared with the within-subject biological variation. Method accuracy is also very important for the comparability of results from different laboratories or instruments.

Blood Chemical Analysis↗
PubMed1993

Acute effects of captopril on the renal actions of furosemide in patients with chronic heart failure.

This study examined the effects of conventional doses of oral captopril on the renal responses to oral furosemide in ambulant patients with stable chronic heart failure. Twenty-five men (mean age 63 years) were randomized to one of two groups. Group 1 received placebo on days 1 and 2 before furosemide. Group 2 received placebo on day 1 before furosemide and captopril thereafter (i.e., captopril before furosemide on day 2). Urine was collected after either placebo or captopril and after furosemide (taken after placebo or captopril pretreatment). Captopril by itself did not affect renal function. Captopril did, however, significantly affect the renal response to furosemide. The increase in urine flow rate after furosemide in group 2 was decreased from 225% with placebo to 128% with captopril (p < 0.02). The increase in sodium excretion after furosemide was decreased from 623% with placebo to 242% with captopril (p < 0.001). Pretreatment with captopril abolished the increase in creatine clearance after furosemide. The increase in urinary albumin excretion (used as a marker of glomerular function) after furosemide was also significantly blunted by captopril. Conventional doses of captopril acutely inhibit the natriuretic and diuretic responses to furosemide at the glomerular level in ambulant patients with stable chronic heart failure.

Administration, Oral↗
PubMed1993

Biological variation of acute phase proteins.

The analytical, within-subject and between-subject components of variation were estimated for serum albumin, transthyretin, alpha 1-acid glycoprotein, alpha 1-antichymotrypsin, haptoglobin, beta 2-microglobulin and C-reactive protein in a cohort of 19 apparently healthy subjects over 20 weeks. Desirable analytical goals based on biological variation should be able to be met except for serum albumin and beta 2-microglobulin for which methodological improvement is warranted. All proteins showed marked individuality which casts doubt on the utility of conventional population-based reference values as interpretative criteria. The critical differences required for significance of changes in serial results differ markedly from protein to protein and the data presented allow generation of objective criteria for monitoring individuals.

Acute-Phase Proteins↗
PubMed1993

Desirable standards for laboratory tests if they are to fulfill medical needs.

Many strategies to define desirable standards for laboratory tests to fulfill medical needs have been proposed over the last three decades. Traditional approaches are based on reference (normal) values, opinions of clinicians, the state of the art, views of experts, data on biological variation, and assessment of the effect of error on clinical use. All these approaches have advantages and disadvantages, but the consensus of experts reached over a decade ago that imprecision desirably be less than one-half of the within-subject biological variation still seems to provide the best set of generally applicable performance standards. Desirable bias is less than one-quarter of the group (within-subject plus between-subject) biological variation. Recent proposals are either restatements of traditional recommendations, further empirical suggestions, or models based on assessment of clinical needs, and have not been widely accepted. Both old and new studies on clinical opinions, sought by using structured questionnaires containing clinical vignettes designed to seek views on the magnitude of significant change, are flawed in design, execution, and data analysis. Until clinicians are more aware of test-result variability and clinical chemists gain quantitative knowledge on the interpretation of test results, it will be difficult to set desirable standards that fulfill actual medical needs, except in a few well-defined screening situations.

Chemistry, Clinical↗
PubMed1992

Analytical goal-setting for monitoring patients when two analytical methods are used.

Serial results from an individual are often obtained using more than one method. Results should be transferable over time and locale. Every method has inherent analytical error, and goals are required to delineate the maximum allowable random (imprecision) and systematic (inaccuracy, bias) errors to facilitate optimal patient care. Based on Harris's proposal [Am J Clin Pathol 1979;72:374-82] that desirable imprecision should be less than or equal to one-half the within-subject biological variation, if the methods have negligible imprecision, then the maximum allowable bias between two methods used for monitoring is one-third of the within-subject biological variation. A more general model has been developed that relates the analytical imprecisions of two methods, and the bias between them, to biological variation. Applying the general formula derived in specific clinical monitoring situations in which a known change in serial results (occurring at a stated probability) stimulates clinical action allows goals for the imprecisions of the two methods and allows the difference in bias between them to be determined quantitatively.

Bias↗
PubMed1992

Proposed quality specifications for the imprecision and inaccuracy of analytical systems for clinical chemistry.

A Working Group of the European Group for the Evaluation of Reagents and Analytical Systems in Laboratory Medicine proposes, after detailed study of the advantages and disadvantages of available strategies, the following quality specifications for analytical systems for clinical chemistry. Total imprecision should be: (a) less than one-half of the average within-subject biological variation, or (b) less than the state of the art achieved by the best 0.20 fractile of laboratories, whichever is the less stringent. The second approach may be used when data on biological variation do not exist. Inaccuracy should be: (a) less than one-quarter of the group (within- plus between-subject) biological variation, or (b) less than one-sixteenth of the reference interval, when data on group biological variation do not exist, or (c) less than twice the ideal imprecision, if the above specifications are too demanding.

Chemistry, Clinical↗
PubMed1991

A novel approach to the assessment of drug compliance in the elderly.

A reliable drug history is not always available, and the constant accurate updating of patients' current medication at a Day Hospital may be difficult. This pilot study examined the use of a qualitative thin-layer chromatographic technique (Toxi-Lab system) applied to urine specimens in assessing drug compliance in the elderly. The system proved capable of detecting 36% of prescribed drugs in a group of elderly patients, and offers a novel and inexpensive approach to monitoring compliance with certain medications.

Aged↗