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Biomedical subjects

C G Fraser

Publications and source records attributed to C G Fraser.

At least 19 recordsLinked to original sources
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↗
PubMed1991

A comparison of analytical goals for haemoglobin A1c assays derived using different strategies.

Analytical goals for the performance characteristics of assays of haemoglobin A1c (HbA1c) have been investigated using different assumptions for generation of estimates, these being based on strategies using data on biological variation and on the clinical use of results. The derived goals are highly dependent on the assumptions made. In general, in monitoring of patients (using results from the same laboratory), the analytical imprecision is the most demanding, whereas bias (inaccuracy) is the most important characteristic when strategies for several centres (laboratories) to achieve similar results are invoked. Goals for analytical quality should be given in a form in which both analytical imprecision and bias (or systematic error) are specified. When several goals are to be considered (for different relevant assumptions), the most demanding should be used.

Diabetes Mellitus, Type 1↗
PubMed1991

Analytical goals for interference.

Objective analytical goals for interference in clinical biochemical methods have not yet been advocated. We propose that, since total analytical error is ideally less than half the within-subject biological coefficient of variation (CVI), the maximum allowable systematic error produced by an interferent (I) is: I less than CVI-(1.96 CVA + SE), where CVA is the relevant experimental analytical imprecision and SE is the systematic error. Such a goal may be applicable also to non-specificity, matrix effects and carryover.

Chemistry Techniques, Analytical↗
PubMed1991

Generation and application of analytical goals in laboratory medicine.

Desirable standards of performance of laboratory tests, termed analytical goals, are required for use in quality assurance, evaluation of methods, reagent kit sets and instruments, discussions with clinicians and gaining additional laboratory resources. Traditionally, goals have been derived from fractions of the reference interval, opinions of clinicians, the state of the art, views of individuals and groups and data on biological variation. All have disadvantages, but the last is currently favoured by many as the best strategy to delineate general goals. Recent more novel approaches have been concerned with the definition of goals for particular clinical situations, but these have not been widely accepted as yet. Further work is required on the setting of goals for performance characteristics other than imprecision and inaccuracy and on the use of goals in the design of effective quality control procedures.

Blood Chemical Analysis↗
PubMed1990

The necessity of achieving good laboratory performance.

The results of clinical biochemistry tests are used in the diagnosis of diabetes mellitus by comparing them with reference values or agreed international criteria. Low analytical imprecision is required so that reference values are not unduly widened by analytical variability. Most laboratory test results are used in monitoring. Low analytical imprecision is required so that changes seen in sequential results reflect stability, amelioration or deterioration, not simply analytical variability. Analytical bias should be absent so that results are (1) comparable in individuals over time as methods evolve and instrumentation changes, (2) equivalent over locale since tests may be done in practitioners' surgeries, outpatient clinics, and laboratories, and (3) able to be interpreted against the fixed criteria. A plethora of strategies have been proposed to set numerical desirable standards of performance, these being termed analytical goals, including use of reference values, opinions of clinicians, state of the art, the views of experts, and data on biological variation. Use of data on within-subject biological variation is currently considered the best approach. A generally applicable goal is that the total error should be less than one-half of the within-subject biological variation. Achievement of this adds about 10% through analytical variability to the true test variability. Analytical goals (CV, %) for glucose, fructosamine, urinary albumin, and haemoglobin A1 assays are 2.2, 2.1, 18, and 3.3%, respectively. These goals are targets worthy of attainment, not inflexible criteria of acceptance or rejection of methods.

Albuminuria↗
PubMed1990

Analytical goals for haematology tests.

All analytical methods can be defined in terms of their practicability and reliability performance characteristics. Desirable standards of performance, or analytical goals, are required for these, particularly for imprecision and inaccuracy. Goals for imprecision have been set using a variety of methods including reference values, opinions of clinicians, views of individuals, and data on biological variation. The last approach is currently favoured; desirable imprecision is equal to or less than one-half of the biological within-subject variation. If this goal is met, total variability of test results is increased by less than about 10% due to analytical variability. Valid estimates of within-subject variability are available for the complete blood count. The goal for inaccuracy is that methods should have no bias so that results are comparable over time and geography; goals based on biological variation should be viewed and used, therefore, as goals for total error. In current practice, some of the goals cannot be met; they should be considered as targets worthy of achievement, not as inflexible criteria of acceptance or rejection of methods.

Blood Chemical Analysis↗