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Biomedical subjects

M Lever

Publications and source records attributed to M Lever.

At least 55 records · Page 3Linked to original sources
PubMed1977

Simulation of laboratory errors and their effects on interlaboratory quality-control programs.

The random errors in an analytical method are additive and can be classified into analytical response-dependent and -independent terms. Non-random errors, caused by systematic faults in the analytical procedure, are not always distriguishable from the random errors, but some cases of non-linear assay response and unsuitable standardisation can be studied usefully in models without random error. Interlaboratory quality control programs cannot distinguish systematic and random error until the pattern of results on a number of specimens, or pairs of specimens, can be studied. In this case linear regression analysis is a powerful method for distinguishing different forms of error especially when response-dependent random errors do not predominate. The range of concentrations used for regression whould be as wide as that in which quantitative distinctions are used in clincal diagnosis and treatment. Preliminary reports, of the results on which the regression analysis is based, are most suitably presented on Youden diagrams with paired specimens.

Analysis of Variance↗
PubMed1977

A design for interlaboratory quality-control programs.

A design for interlaboratory quality-control programs is described. Speimens are despatched in pairs to participating laboratories. The results returned by laboratories are compared with each other and with reference results, but the frequent brief reports which are prepared are not regarded as the main laboratory assessments, although these reports can alert laboratories to gross imprecision and inaccuracy. When sufficient results have been returned, a linear regression analysis is carried out between results from each laboratory and the reference results. The statistics obtained from the regression data provide a concise source of information about the form of inaccuracy (imprecision and systematic error) present.

Chemistry, Clinical↗
PubMed1976

Contributions of other sterols to the estimation of cholesterol.

The responses of 5alpha-cholestan-3beta-ol, 5alpha-cholest-7-ene-3beta-ol and cholesta-5,7-dien-3beta-ol, normally found in human serum, were examined by: (1) the Liebermann-Burchard reaction, (2) the Zak (ferric chloride) reaction, (3) an enzymatic cholesterol method monitored by estimating the amount of hydrogen peroxide produced, (4) an enzymatic cholesterol method monitored by observing the change in absorbance at 240 nm, and (5) gas chromatography. The results show that none of these methods is specific for cholesterol; contributions from the sterols examined range from zero to more than 150% relative to cholesterol. For the first four methods contributions depend on the conditions under which each test is performed.

Cholestadienols↗