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Biomedical subjects

C G Fraser

Publications and source records attributed to C G Fraser.

At least 73 records · Page 4Linked to original sources
PubMed1989

Biologic variation of common hematologic laboratory quantities in the elderly.

Analytic, within-subject, and between-subject biologic variations were estimated for leukocytes, erythrocytes, hemoglobin, hematocrit, mean cell volume (MCV), mean cell hemoglobin (MCH), mean cell hemoglobin content (MCHC), platelets, and a three-component differential count (lymphocytes, monocytes, and granulocytes in terms of both concentration and percentage of leukocytes) in cohorts of 12 male and 12 female healthy elderly subjects. The assays were performed with an Ortho ELT-800 automated analyzer. The estimates of within-subject biologic variation were similar to published data on young subjects, indicating that this aspect of homeostasis is not compromised in the elderly. The data were used to derive objective analytic goals; goals were surpassed except for assays of erythrocytes, hematocrit, and the derived MCV, MCH, and MCHC. The changes required for serial results to be significantly different were determined and found to be generally valid because most quantities have no heterogeneity of within-subject variation. All quantities had significant individuality; in consequence, conventional population-based reference values are of limited utility, and screening using reference limits will not detect latent or early disease in many subjects.

Aged↗
PubMed1989

Clinical utility of assays of glycosylated haemoglobin and serum fructosamine compared: use of data on biological variation.

Assessment of the relative clinical usefulness of glycosylated haemoglobin (HbA1) and serum fructosamine is complicated by their markedly different half-lives. They have therefore been compared using a number of indices derived from data on biological variation, as applied in a study of blood glucose control in newly diagnosed diabetic patients. The within-subject (CVI) and between-subject (CVG) variation of fructosamine and HbA1 were assessed in 8 stable diabetic patients. A slightly smaller relative change, or critical difference, is required between serial HbA1 results than between fructosamine results before a significant change can be said to have occurred. The heterogeneity of within-subject variance is also less for HbA1, rendering the critical difference more generally applicable. HbA1 may therefore be more appropriate for long-term monitoring. Monitoring of blood glucose control of a group of 26 newly diagnosed diabetic patients before the commencement of therapy and 1, 2, and 3 months later by serum fructosamine or HbA1 provided very similar information. Fructosamine responds more rapidly with changes of blood glucose control. However, whether this confers any clinical advantage will depend upon the frequency of testing.

Aged↗
PubMed1989

Total amylase and pancreatic isoamylase in serum and urine: considerations from data on biological variation.

The analytical, within-subject and between-subject components of variation were estimated for amylase activity and pancreatic isoamylase activity in serum measured using newer analytical methods. Desirable analytical imprecisions based on within-subject variation were CV less than or equal to 4.4% and CV less than or equal to 7.0%, respectively. Conventional population-based reference intervals were not useful because of marked individuality; clinical decision-making points should be derived from the desired sensitivity and specificity. Serial results must change more than about 30% and 40% respectively before significance (P less than or equal to 0.05) can be claimed. Similar data on total amylase and pancreatic isoamylase activities in random and first morning urines showed that the use of conventional reference intervals was appropriate. Very large changes (greater than 100%) were required before a difference in serial results was significant. Calculation of the urine amylase/creatinine ratio appeared to confer no advantage. Derivation of the ratio of pancreatic isoamylase to total amylase activity in serum or urine was unlikely to provide additional information of value in either diagnosis or monitoring.

Adult↗
PubMed1989

Generation and application of data on biological variation in clinical chemistry.

Most clinical chemical analytes vary in a random manner around a homeostatic set point. Replicate analyses of a series of specimens collected from a group of subjects allows estimation of analytical, within and between subject components of variation. The preferred experimental procedures and statistical methods for evaluation of data and analysis of variance are described; a detailed example is provided in the Appendix. The many uses of data on biological variation in clinical chemistry are reviewed, including setting analytical goals, deciding the significance of changes in serial results from an individual, evaluating the utility of conventional population-based reference values in patient management, and other applications.

Analysis of Variance↗
PubMed1989

Biological variation of urinary N-acetyl-beta-D-glucosaminidase: practical and clinical implications.

The analytical, within-subject, and between-subject components of variation of N-acetyl-beta-D-glucosaminidase (NAG) were estimated from duplicate assays of 10 timed first morning and 10 untimed urine specimens collected from each of 15 ostensibly healthy individuals. Results were expressed in terms of activity, NAG/creatinine ratio, and excretion rate. Current analytical methods can achieve desirable performance standards. NAG has little individuality, and conventional population-based reference intervals are therefore useful. In view of the practicability and relatively low within-subject variation, for routine clinical purposes we prefer assay of NAG in first morning urine, expressing the results in terms of activity. Using the results of assays of different specimens, we found that the correlation between urinary albumin and NAG varied considerably, owing to the large intrinsic variability of both analytes; this might explain previous conflicting results.

Acetylglucosaminidase↗
PubMed1989

Biological variability of 26 clinical chemistry analytes in elderly people.

Analytical, within-subject, and between-subject components of variation were estimated for 26 clinical chemistry analytes from duplicate analyses of 10 specimens collected from 27 healthy elderly subjects over a period of 20 weeks. Within-subject variations were similar to those generated previously by us in younger subjects. We conclude, therefore, that homeostasis is not compromised by age alone, and biological variability does not increase simply with age. All analytes except serum water had marked individuality, showing that conventional population-based reference values are of limited utility. The critical differences required for two results to be significantly (P less than or equal to 0.05) changed are not the same as those that prompt action by clinicians. Although heterogeneity of within-subject variation does exist, we believe that the critical differences generated will be useful in routine clinical decision making.

Adult↗
PubMed1989

International Federation of Clinical Chemistry Education Division and International Union of Pure and Applied Chemistry Clinical Chemistry Division Commission on Teaching of Clinical Chemistry. Guidelines (1988) for training in clinical laboratory management.

Trainees in laboratory medicine must develop skills in laboratory management. Guidelines are detailed for laboratory staff in training, directors responsible for staff development and professional bodies wishing to generate material appropriate to their needs. The syllabus delineates the knowledge base required and includes laboratory planning and organisation, control of operations, methodology and instrumentation, data management and statistics, financial management, clinical use of tests, communication, personnel management and training, and research and development. Methods for achievement of the skills required are suggested. A bibliography of IFCC publications and other material is provided to assist in training in laboratory management.

Chemistry, Clinical↗
PubMed1989

International Federation of Clinical Chemistry (IFCC), Education Division. Guidelines (1988) for training in clinical laboratory management.

Trainees in laboratory medicine must develop skills in laboratory management. Guidelines are detailed for laboratory staff in training, directors responsible for staff development and professional bodies wishing to generate material appropriate to their needs. The syllabus delineates the knowledge base required and includes laboratory planning and organisation, control of operations, methodology and instrumentation, data management and statistics, financial management, clinical use of tests, communication, personnel management and training, and research and development. Methods for achievement of the skills required are suggested. A bibliography of IFCC publications and other material is provided to assist in training in laboratory management.

Chemistry, Clinical↗
PubMed1988

Biological variation of serum and urine creatinine and creatinine clearance: ramifications for interpretation of results and patient care.

Analytical and intra- and inter-individual components of variation were assessed over a 40-week period in 15 apparently healthy subjects, seven men and eight women, for serum creatinine, urine creatinine expressed in both concentration and output terms, and creatinine clearance, both uncorrected and corrected to standard surface area of 1.73 m2. Serum creatinine, even when considered separately for men and women, has marked individuality, and conventional population-based reference ranges are consequently of limited value. In contrast, urinary creatinine and creatinine clearance have less individuality, and reference ranges are more useful. Desirable analytical standards are not attained for serum creatinine assays, but are achieved for urine creatinine and clearance determinations. Creatinine clearance is, therefore, the favoured first-line test for initial assessment of patients. However, the small critical difference required for two serum creatinine results to be significantly different, and the comparatively large critical difference for clearance, make serial serum creatinine assays more useful for monitoring individuals.

Adult↗
PubMed1988

Variability of capillary plasma glucose in healthy individuals in repeated 75 g oral glucose tolerance tests.

A series of ten 75 g oral glucose tolerance tests was carried out on each of 14 apparently healthy subjects. The analytical, intra-individual and interindividual components of variation were calculated by nested ANOVA following duplicate analyses of capillary plasma glucose under optimal conditions. The analyses met the objectively set analytical goal of CV less than or equal to 2.2%. There was considerable intra-individual variation, but no subject was ever classified as diabetic or having impaired glucose tolerance. Recent criteria for interpretation of results must be used since conventional population-based reference values are not adequate. Serial results from an individual must differ by more than 0.7 mmol/L for fasting specimens and at least 1.6 mmol/L for other specimens for a statistically significant (P less than or equal to 0.05) change to have occurred.

Administration, Oral↗
PubMed1988

Desirable performance characteristics and clinical utility of immunoglobulin and light-chain assays derived from data on biological variation.

Using automated assays of IgG, IgA, and IgM, and kappa (kappa) and lambda (lambda) light-chains, we assessed the analytical, intra-individual, and interindividual components of variation in a cohort of 12 apparently healthy subjects to examine the utility of the Kallestad Immunochemical Evaluation system. The immunoglobulins and light-chains had small intra-individual variation, and, in consequence, good analytical precisions (CV) of 2.3%, 2.5%, 3.0%, 2.4%, and 2.4% are required for IgG, IgA, IgM, kappa, and lambda assays, respectively. All of these analytes, and the derived kappa/lambda and heavy-/light-chain ratios, have marked individuality. Conventional population-based reference values are of limited utility; therefore, the assays are unlikely to have high diagnostic sensitivity but will be very useful for monitoring individuals. The kappa/lambda ratio may be of particular value in monitoring because a change exceeding 4% does imply a significant (P less than or equal to 0.05) difference in serial results.

Adult↗
PubMed1988

The application of theoretical goals based on biological variation data in proficiency testing.

Proficiency testing schemes must define acceptable standards of performance. A number of strategies have been used to define acceptable standards, or analytical goals, for imprecision, but it does appear that the current widely held view is that imprecision (as SD or coefficient of variation) should be equal to or less than one half of the average intraindividual biological variation. Since the goal for inaccuracy is that results should be unbiased, the biological variation-based goals should be used for total laboratory error. Many data on the biological variation of a wide range of analytes now exist, which facilitates goal-setting. Current proficiency testing schemes generally analyze laboratory data using either a parametric statistical approach or empirical fixed limits of acceptability. The latter strategy appears to have advantages provided that the criteria of acceptability are the objective biological variation-based goals.

Academies and Institutes↗