Whole-blood test for total cholesterol by a self-metering, self-timing disposable device with built-in quality control.

A whole-blood test for total cholesterol has been developed that is performed in a low-cost disposable flow device without user intervention (after sample addition). The device meters the sample, separates plasma from erythrocytes, and precisely times plasma flow into various reagent compartments, including a quality-assurance chamber. Test results are displayed as a well-defined and easily readable color bar. A quality-control window attests to the integrity of the test components. Here, we describe the assembly and individual functions of the device and report its performance characteristics. Precision and accuracy studies in four clinical studies at independent locations yielded total imprecision of <5% and an average bias of 1.35% vs the Abell-Kendall method.

Novel reagent and method for direct determination of chloride in serum with a centrifugal analyzer.

We report a novel reagent containing ferric perchlorate, perchloric acid, and polyoxyethylene (23) lauryl ether (Brij 35) with which the concentration of chloride in serum can be measured. We applied this reagent to use with a centrifugal analyzer (CentrifiChem 400) in a dynamic bichromatic procedure, resulting in broad linearity of the standard curve (0-180 mmol/L), short analysis time (1 min), and little interference from bilirubin, hemoglobin, turbidity, or bromide ions. The reagent is simple, contains no mercury, and the combination of low acid concentration and surfactant prevents serum protein precipitation. Precision is good (for x- = 93 mmol/L, CV = 1.55%), and results correlate well with those obtained by coulometry (r = 0.974).

Optimized method for measuring aspartate aminotransferase activity with the CentrifiChem Analyzer, with automatic preincubation of serum.

We propose a routine method for the mechanized measurement of aspartate aminotransferase with the CentrifiChem Analyzer, which is based on the recommendations of both the International Federation of Clinical Chemistry and the Société Française de Biologie Clinique. A modification of the CentrifiChem pipettor permits simultaneous pipetting of two reagents, thus achieving automatic preincubation of the serum in the transfer disk. Owing to the fixed reagent volumes dispensed by the pipettor, preincubation conditions had to be modified, but the recommendations for the final reagent concentrations in the assay cuvet were observed. The totally automated method correlates very well with one involving manual pipetting to reproduce the detailed step-by-step recommendations of the International Federation of Clinical Chemistry. Intra-assay precision ranged from 3.4 to 4.9% and interassay precision from 1.7 to 7.5%. We assayed 135 sera and obtained a correlation coefficient of 0.996 (a = 1.025, b = 0.08).

Automated radioimmunoassay of choriomammotropin (human placental lactogen).

We describe a totally automated procedure for radioimmunoassay of choriomammotropin, in which all phases of the assay are automated in a single system ("Centria"). This system permits the simultaneous incubation and separation of many samples in a nonequilibrium assay, and measurements are obtained in less than 30 min. Results for clinical samples by reference radioimmunossay methodology and with the Centria system compared uniformly well: y=0.91x - 0.87;r=0.94. The coefficient of variation for samples run in duplicate on the same day was 5.2%, 7.4% for samples run on different days. The specificity, sensitivity, simplicity, and speed of this system makes it a useful new tool for kinetic, nonequilibrium immunoassay.

Simplified, totally enzymatic method for determination of serum triglycerides with a centrifugal analyzer.

We describe a totally enzymatic method for determination of serum triglycerides (triacylglycerols) specifically adaptable to the CentrifiChem system. The method involves lipolysis with lipase from Rhizopus arrhizus alone and quantitation of the resulting glycerol with glycerol dehydrogenase in a kinetic, fixed-time mode. Hydrolysis by the lipase is complete, for concentrations up to at least 5.0 g/liter, in 10 min at room temperature. The unfavorable equilibrium for the oxidation of glycerol is overcome by increasing the pH and adding excess NAD+. Under these conditions the glycerol determination is linear to at least 4.0 g of glycerol per liter, as triglyceride. The test exhibits acceptable accuracy and precision, and results correlate well with those by an alternative totally enzymatic procedure. The present method is unaffected by phosphatase and a considerably simplified reagent is used.

Adaptation of a T3-uptake test and of radioimmunoassays for serum digoxin, thyroxine, and triiodothyronine to an automated radioimmunoassay system--"Centria".

We report the adaptation of four radioassays to the prototype of an automated radioimmunoassay system ("Centria," Union Carbide). The system consists of three integrated modules: (a) an automated pipettor, which dispenses samples and reagents; (b) the key module, an incubator/separator, in which centrifugal force is used to initiate and terminate multiple radioassay incubations and separations simultaneously; and (c) a gamma-counter/computer, which counts three tubes simultaneously and converts counts into concentration units. Radioimmunoassays for thyroxine, triiodothyronine, and digoxin were developed with use of well-characterized antibodies and of prepackaged Sephadex-containing columns to separate bound and free radioactive ligand. A triiodothyronine-uptake test in which the same kind of columns were used was also adapted to the instrument. Results for clinical samples compared favorably with those obtained by manual procedures. We report data on correlation between different methods and preliminary data on precision of the prototype system.