Determination of copper, zinc, and selenium in human plasma and urine samples by potentiometric stripping analysis and constant current stripping analysis.

Potentiometric stripping analysis and constant current stripping analysis are proposed as routine methods for analysis of copper, zinc and selenium in plasma and urine samples. The analytical performance of these methods is comparable with that reported for atomic absorption spectrometry. However the low cost, greater simplicity of the apparatus, and the facility of execution make this methodology a valid candidate for routine application in Clinical Chemistry laboratories.

Enzymatic determinations in acute rejection after liver transplantation: preliminary report on necrosis index.

The catalytic activities of some mitochondrial and cytoplasmic enzymes were measured in plasma from 19 patients after orthotopic liver transplantation, in order to detect and monitor the evolution of hepatocellular damage and to predict liver rejection. The enzymatic activities determined were: mitochondrial isoenzyme of aspartate aminotransferase, glutamate dehydrogenase, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyltranspeptidase and alkaline phosphatase. The results of all enzymatic activities were normalized by expressing them as multiples of the upper limit of the relevant reference range and then the necrosis index (NI) has been calculated. The proposed NI consists of percent ratio of the normalized mitochondrial enzymatic activities over the sum of cytoplasmic and mitochondrial normalized activities. We observed that NI values higher than 30% correctly identified all but two acute rejection events which were documented by liver biopsies showing a diagnostic sensitivity of 90%, specificity of 78% and a predictive value of 90%.

Influence of serum proteins on fructosamine concentration in multiple myeloma.

Serum fructosamine levels in 36 subjects with various types of multiple myeloma and in 64 normal controls were evaluated by means of a Nitroblue tetrazolium colorimetric assay. Only the IgA myeloma group showed significantly raised serum fructosamine values (P less than 0.001). In the IgG myeloma group, which showed a higher mean serum protein concentration, serum fructosamine levels were not significantly different from controls. The study shows that elevated IgA levels do influence serum fructosamine and this effect should be taken into due consideration in order to avoid possible misinterpretations in evaluating this widely used index of glucose metabolism.

Long-term retrospective control procedures for monitoring analytical performance of laboratory instruments.

We propose a statistical procedure for long-term quality-control of laboratory instruments, including daily, day-to-day, and monthly evaluations. The procedure is based on the unique and unequivocal interpretation of five results for control sera by calculation of a Reliability Index and further manipulations of this unitless parameter. This method, which we have tested during the past two years, allows for monitoring analytical performance and making comparisons with results of interlaboratory surveys. The monthly analytical variability, expressed as "total error," is an indicator of the clinical usefulness of analytical results.

Real time control procedures for monitoring SMAC analytical performance.

A system has been developed in our Hospital Clinical Chemistry Laboratory with the aid of a minicomputer on line with SMAC. The programs are in Basic and comprise management of patient samples and of reference sera, on-line acquisition of analytical data, checks of error reporting and of abnormal result values, real time processing of quality control parameters and data transfer on floppy disk. An efficient and easy monitoring of the chemical procedures and result reliability is achieved together with instrument performance optimization.

Subcellular distribution of some specific enzymatic activities in human leucocytes.

The activities and subcellular distribution of the following enzymes: NADH oxidase, alkaline phosphatase, beta-glucuronidase and ATPase, were assayed in human mononuclear and polymorphonuclear leucocytes and in particular the contamination and integrity of the mitochondrial fractions were evaluated with this new separation procedure. Results show that maximal contamination was found to be that from lysosomal beta-glucuronidase especially in polymorphonuclear leucocyte mitochondria fractions. Furthermore oligomycin-sensitive ATPase data suggest that mitochondria do not decrease in number or lose their integrity to a great extent. Controversial p-nitrophenyl-phosphatase activity was also found to be present in polymorphonuclear and mononuclear leucocytes granular-soluble fractions.