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E M Gowans

Publications and source records attributed to E M Gowans.

8 recordsLinked to original sources
PubMed1989

Analytical goals for the estimation of non-Gaussian reference intervals.

Goals for analytical quality are postulated for the situation in which a number of laboratories will share common reference intervals for some quantities for which the population is homogeneous. These goals are evaluated on the assumption that the acceptable combined analytical bias and imprecision should not allow the percentage of the population outside either upper or lower reference limits to exceed the interval 1.3 to 4.4%. The goals are evaluated for log-Gaussian biological distributions, and for distributions which can be transformed into log-Gaussian by addition of a constant value to all elements. Further analytical goals for non-parametric distributions are discussed. For log-Gaussian distributions the maximum allowable bias and imprecision are dependent on the ratio of the upper and lower reference limits. When this ratio is c. 1.25, the bias alone must be less than 1.5% or the coefficient of variation alone less than 3.5%. For a ratio of 10, these values may be as high as 15% and 34%, respectively.

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

Analytical goals for the acceptance of common reference intervals for laboratories throughout a geographical area.

Analytical goals required for the successful transfer of reference intervals between laboratories within a specified limited geographical area, with a population homogeneous for the quantities, are presented. Diagrams are shown which allow the investigation of the influence of analytical imprecision and bias, both separately and in combination, on the percentage of the population outside each reference limit. Figures to evaluate the effect of population sample size on the size of confidence interval around each reference limit are combined with the diagrams for analytical imprecision and bias. The maximum acceptable percentage of the population outside the limit for the 0.90 confidence interval of each of the means +/- 1.96 s reference limits is 4.6% for a population sample size of 120. Based on this, the maximum acceptable imprecision, with no bias, is 0.6 of the total biological standard deviation (sB) and the maximum acceptable bias, with no imprecision, is 0.25 sB.

Chemistry Techniques, Analytical↗
PubMed1987

Biological variation in analyte concentrations in urine of apparently healthy men and women.

Analytical, intra-individual, and interindividual components of variation for sodium, potassium, urea, creatinine, calcium, and phosphate were estimated from results for 24-h urine specimens collected from 15 apparently healthy individuals every four weeks for 40 weeks. Expressed as output, mean values differed for men and women, except for calcium. Our data on intra-individual variation were similar to those obtained for 10 men by Shephard et al. (Clin Chem 1981;27:569-73). Calculated analytical goals are easily attained by current methods. Reference values for urine creatinine are useful only when expressed as output and stratified according to gender. The ratios of intra- to interindividual variation generally increase on such stratification; separate reference values for men and women are therefore required for analytes expressed as output. Measurements of sodium and potassium in urine should be reported as concentration, but output terms are favored for the other analytes. Differences for two serial results from an individual must be rather large to differ statistically.

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↗