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C G Fraser

Publications and source records attributed to C G Fraser.

At least 109 records · Page 6Linked to original sources
PubMed1986

Analytical goals for glucose analyses.

Analytical goals may be defined as those standards of performance required to facilitate optimal patient care. Review of the considerable amount of published work on glucose analyses allows delineation of the following current goals: For plasma glucose: within-laboratory between-batch imprecision--CV less than or equal to 2.2%; inaccuracy - no bias; linearity - 1 to 28 mmol/L; detection limit - 1 mmol/L; turnaround time - 30 min (in emergency situations). For urine glucose (quantitative): within-laboratory between-batch imprecision - SD less than or equal to 0.1 mmol/L; inaccuracy - no bias. For urine glucose (qualitative or semi-quantitative): negative - should be negative; positive - should be positive +/- one positive colour block; detection limit - 2.8 mmol/L. Moreover, each laboratory should develop goals for the many pre-analytical factors affecting glucose analyses. While the above goals are not always achieved in current practice, they are attainable and are worthy targets to strive to reach. The general principles discussed here for glucose analyses are applicable to other analytes of interest to the clinical biochemist.

Blood Glucose↗
PubMed1986

Intra- and interindividual biological variation of five analytes used in assessing thyroid function: implications for necessary standards of performance and the interpretation of results.

Intra- and interindividual components of biological variation have been determined for total thyroxin (TT4), free thyroxin (FT4), total triiodothyronine (TT3), free triiodothyronine (FT3), and thyrotropin (TSH). Calculated analytical goals (CV, %) for the precision required for optimal patient care are: TT4 less than or equal to 2.5, FT4 less than or equal to 4.7, TT3 less than or equal to 5.2, FT3 less than or equal to 3.9, and TSH less than or equal to 8.1. The marked degree of individuality demonstrated for all hormones indicates that, if conventional population-based reference ranges are used uncritically, major changes in hormone concentration may not be correctly identified for some patients because observed values continue to lie within the reference range. At analyte concentrations approximating the mean values found in this study, and for analytical performance meeting the appropriate analytical goal, the differences required for consecutive results to be significantly different (p less than or equal to 0.5) have been calculated as: TT4, 14.7 nmol/L; FT4, 5.7 pmol/L; TT3, 0.6 nmol/L; FT3, 1.3 pmol/L, and TSH, 0.7 milli-int. unit/L.

Adult↗
PubMed1986

Five methods for determining urinary calcium compared.

We compared frequently used methods for calcium in urine with respect to linearity, analytical recovery, within- and between-batch imprecision, bias, and practicability. We assayed serum, lyophilized urine, native urine, and an aqueous reference solution of calcium carbonate. We found that atomic absorption spectrometry and the Corning 940 Analyzer have the widest ranges of linearity; the methylthymol blue method has the poorest analytical recovery. All methods--the aforementioned three plus the Du Pont aca and Technicon RA-1000 methods--had acceptable precision, although random errors were found with the methylthymol blue method, and, except for one type of commercial lyophilized urine assayed by the Technicon method, there were no matrix problems or difficulties with bias. We cannot recommend the methylthymol blue method, but evidently urinary calcium assays can be adequately done with many currently available methods. Intralaboratory attention to methodology should give improved performance in assessment programs.

Bromthymol Blue↗
PubMed1985

Better laboratory evaluations of instruments and kits are required.

There are many published protocols for evaluating instruments and reagent-kit sets, and a plethora of papers describe the results of evaluations performed. It might be assumed, therefore, that this facet of clinical chemistry has no problems, but examination of evaluations of instruments published in the first half of 1984 shows flaws in some aspects of experimental design and execution, statistical analysis, and interpretation of data. We believe that clinical chemists, manufacturers and suppliers, and journal editors and referees can all contribute to improvement of this situation, and we suggest some guidelines for each of these groups.

Chemistry Techniques, Analytical↗
PubMed1984

Evolution of a national urine quality assurance programme: the Australasian experience, 1981-1983.

A national interlaboratory quality assurance programme for quantitative urine analysis has been conducted over the past three years in Australasia under the auspices of the Royal College of Pathologists of Australasia and the Australian Association of Clinical Biochemists. Analysis of urine calcium has consistently improved over the three year period whereas urine protein analysis has consistently declined. Based on the findings in 1983, it is considered that urine sodium, potassium, creatinine, phosphate, glucose, and chloride are currently being measured satisfactorily by Australasian laboratories, while the analyses of urine proteins, urate, oxalate, 5-hydroxyindoleacetic acid and 4-hydroxy-3-methoxymandelic acid still require substantial improvement.

Australia↗
PubMed1984

The effect of instrument variables on calculation factors for standardisation of colorimetric analyses.

A number of colorimetric methods, particularly enzyme activity assays, are usually standardised using calculation factors based on the molar absorptivity of a principle reactant or product. Such methods are subject to long-term variation. The relationship between long-term variation in results and instrument variables affecting calculation factors has not been quantitated. In this study, we have shown that, on a centrifugal analyser having a within-run coefficient of variation of less than 1%, instrument variables affecting calculation factor alone could result in changes in results of up to 8.5% over 75 days. We therefore advocate daily use of a solution of potassium dichromate to monitor instrument variables that can independently affect calculation factors and within-run imprecision. This procedure is useful for maintaining long-term performance and for differentiating problems of instrumental or chemical origin.

Autoanalysis↗
PubMed1984

An inter-laboratory quality-assurance survey of emergency clinical biochemistry tests.

One hundred and thirteen Australian laboratories participated in a state-of-the-art quality-assurance survey of emergency clinical biochemistry tests. Two liquid-reconstituted lyophilised human-based serum samples, which had previously been analysed in the national general serum chemistry programme, were sent by air cargo, together with their own previously completed request forms, for analysis as emergency tests on a previously nominated date. The standard of performance of ten of the eleven most commonly performed tests was inferior to that obtained on a routine basis, as judged by the number of results outside present limits of total laboratory error from target values which had been previously set by reference laboratories. The standard of analytical performance achieved for emergency tests can and should be improved.

Australia↗