Clinical chemistry
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Comparative Study
Comparison of product moment and rank correlation coefficients in the assessment of laboratory method-comparison data.
We have studied the effects of range and distribution of data on product moment and rank correlation coefficients when deviation from a linear relationship was due solely to experimentally produced random error. All correlation coefficients (Pearson r, Spearman rho, and Kendall tau) were markedly influenced by the range of the data, and, for the rank correlation coefficients, the effect of range varied for different data distributions. ⋯ Thus, neither product moment nor rank correlation coefficients are of value in analysis of laboraoty method-comparison data. The standard deviation of the residual error of regression should be calculated as a measure of the random error about the regression line.
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Comparative Study
Simultaneously obtained skin-puncture serum, skin-puncture plasma, and venous serum compared, and effects of warming the skin before puncture.
Specimens of skin-puncture serum and plasma and venous serum were simultaneously obtained from healthy adults and in each specimen the concentrations of 12 chemical constituents were measured. No clinically important difference was found in the concentrations of the constituents measured in skin-puncture serum and plasma with or without warming the skin before puncture. When the concentration of each of the measured constituents was compared in skin-puncture specimens and venous serum there were important differences in the concentrations of glucose, potassium, total protein, and calcium. ⋯ The degree of hemolysis was the same in skin-puncture serum and plasma, but less in venous serum. The greater hemolysis in skin-puncture specimens was not reflected in a clinically important increase in the values of lactate dehydrogenase and potassium. We conclude that there is a difference in the concentration of some chemical constituents in skin-puncture specimens and venous serum and that these differences should be considered when results for these types of specimens are compared.
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Continuous monitoring of heat denaturation of a mixture of alkaline phosphatase isoenzymes at 60 degrees C and pH 7.5 permits the simultaneous direct identification and quantitation of three isoenzymes: the placental isoenzyme, the L-phenylalanine-sensitive intestinal isoenzyme, and the liver isoenzyme (hepatocytic). The isoenzyme that is principally of bone origin cannot be identified as such without the help of other diagnostic aids and the patient's medical history. All human tissues contain alkaline phosphatase, many organs more than one of the isoenzymes. ⋯ Liver alkaline phosphatase activity increases in the blood early in liver disease, before most liver tests show abnormalities. The other major isoenzyme of normal serum probably represents a mixture of isoenzymes from bone and reticulo-endothelial and vascular tissues, which all contain the same "very heat-labile" alkaline phosphatase. Cord blood and children's sera contain mostly this very heat-labile isoenzyme.
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Review Comparative Study
Calculations and correction factors used in determination of blood pH and blood gases.