Clin Chem Lab Med
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Interpretation of laboratory test results requires comparison to some type of reference value or reference interval. These comparisons can be cross-sectional (population-based reference interval and cut-off values) or longitudinal (reference change value). Quality specifications for cross-sectional comparison have been established by determining the influence of analytical bias and imprecision on the percentage of the healthy population falling outside the reference limits, when sharing population-based reference intervals in a Gaussian distribution of results. ⋯ In this chapter we discuss the clinical considerations and laboratory-related factors that must be considered when quality specifications are applied to sharing reference comparisons. Real life experience shows that different analytical methods can produce comparable results when common quality goals are established, and quality can be achieved through a willingness to work together. Within the existing organization, the current specifications for analytical quality and a dedication to quality health care makes it possible to achieve transferability between laboratories within a geographic area.
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Comparative Study Clinical Trial
Clinical utility of serum holotranscobalamin as a marker of cobalamin status in elderly patients with neuropsychiatric symptoms.
Early diagnosis of cobalamin deficiency is crucial, owing to the latent nature of this disorder and the resulting possible irreversible neurological damage. A normal serum cobalamin concentration does not reliably rule out a functional cobalamin deficiency and there does not at present seem to be any single diagnostic approach to achieve this diagnosis. A new marker for cobalamin status is the serum concentration of cobalamin bound to transcobalamin II (holoTC). ⋯ This may indicate poor specificity of low holoTC for cobalamin deficiency. In 23 out of 176 patients with normal levels of holoTC we observed pathological levels of other markers for cobalamin deficiency. The use of holoTC in the present study group did not give significant additional information other than that given by serum cobalamin and therefore cannot be recommended in this clinical setting.
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Practice Guideline Guideline
Guideline for the production of multicentre physiological reference values using the same measurement system. A proposal of the Catalan Association for Clinical Laboratory Sciences.
This article is intended as a guide for the production of biological reference values of healthy people (physiological reference values) by several clinical laboratories using the same measurement system. This guide is a proposal from the Catalan Association of Clinical Laboratory Sciences to be applied worldwide at a regional level. This guide makes it possible for all clinical laboratories in a region using the same measurement system to adopt the same physiological reference limits. The model presented here is based on the assumption that the production of physiological reference values is a professional task that should be shared by both clinical laboratories and the in vitro diagnostics industry.
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Internal quality control should assure that the desired quality goals are achieved during reference value studies. Quality goals are often stated in the form of allowable limits of error, such as an allowable total error or an allowable bias. ⋯ A graphical tool, called the critical-error graph, facilitates the selection by superimposing the calculated critical systematic error on the power curves of different control rules and numbers of control measurements. Examples are provided to illustrate the calculation of the critical systematic error from both an allowable total error goal and an allowable bias goal, using figures from an extensive tabulation of available total error and bias goals.
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Editorial Review
Reference values: from philosophy to a tool for laboratory medicine.