Reference standardization and analytical performance of a liquid homogeneous high-density lipoprotein cholesterol method compared with chemical precipitation method.

Background: The use of high-density lipoprotein cholesterol (HDL-C) levels as a risk factor for coronary heart disease necessitates an accurate and precise method for measuring HDL-C. The Centers for Disease Control and Prevention HDL-C reference method (RM) and designated comparison method (DCM) are time-consuming, expensive, and impractical for routine clinical use. We evaluated the Liquid N-geneous (LN-gen) HDL-C assay (Genzyme Diagnostics, Cambridge, Mass) to determine if this homogeneous reagent meets the National Cholesterol Education Program requirements for HDL-C evaluation.

Serum iron and proficiency testing: a dilemma.

We present and discuss observations regarding the results of the serum iron determination as seen in various surveys. The reference method proved to score different in our hands judging on the performance in the Dutch and German quality assessment schemes. Furthermore, it is clear and frustrating that these scores, representing the most accurate results, are becoming more and more labeled "out of acceptable range".

Further studies on the standardization of neonatal bilirubin.

Certain problems in the standardization of direct-reading instruments (bilirubinometers) were investigated. It was shown that the combination of wavelength setting and choice of pH is very important with respect to the standard to be used. It is emphasized that in fact there is no synthetic bilirubin standard which can be used as primary standard.

Reflections on the standardization of total bilirubin in neonatal serum.

A study is described on the standardization of the determination of neonatal total bilirubin. A wide variation in results was shown in surveys held in The Netherlands and Germany and the reasons for this variation were sought. The suitability of commercial bilirubin standards and direct reading instruments, widely used in the neonatal field, was tested by comparing all measurements with those obtained with the candidate reference method.

Spinal fluid protein revisited: a reappraisal of the biuret procedure.

In this study our previously described selected method, a biuret procedure with deproteinization, for the determination of spinal fluid protein is thoroughly discussed against the background of the results found with a number of Lowry modifications. The use of various separation techniques, i.e.