CVs Range Research Articles

A nephelometry system for the Abbott TDx analyzer.

A self-contained light-scattering accessory carousel has been developed for the Abbott TDx fluorescence polarization analyzer, extending the instrument's capabilities to nephelometric methods of analysis, including assays for specific proteins by immunoprecipitation: IgG, IgA, IgM, and transferrin. The scattered light from a green-light-emitting diode (peak wavelength 565 nm) is measured at an angle of 37.5 degrees by the existing optical detection system of the TDx analyzer without modification of the instrument. Measurements are made at quasi-equilibrium, with sample blank correction. No sample pretreatment is required, and antigen-excess is checked automatically. CVs range from 3 to 6% (within-run) and 7 to 9%. (total). Calibration curves may be stored for at least two weeks. A nephelometric method for monitoring chromogenic reactions in the green wavelength region is also described. This method--Scattered Energy Attenuation (SEA)--has been used in preliminary experiments to measure calcium, total protein, iron, and bilirubin.

A thyrotropin radioimmunoassay kit evaluated vs two reference assays.

We evaluated a double-antibody radioimmunoassay kit for thyrotropin that includes calibrators prepared in a matrix of human serum and involves overnight nonequilibrium. Results were compared with those from two reference assays for thyrotropin. The range of within-assay CVs for the kit for thyrotropin values between 0.9 and 2.4 milli-int. units/L was 2.2 to 5.3%, that for between-assay CVs was 8.3 to 30%. The estimated minimum detectable concentration of thyrotropin was 0.6 milli-int. unit/L. We saw no cross reactivity with human choriogonadotropin by any of 48 sera from pregnant women. The original lot of serum specified as thyrotropin-free contained small but measurable amounts of thyrotropin; a second lot did not. Clinical data generated with the kit and the reference assays correlated well and were consistent with the clinical status of various categories of patients.

Liquid-chromatographic assay and identification of mono- and diester conjugates of bilirubin in normal serum.

This liquid-chromatographic procedure for determining bilirubin mono- and diester conjugates in normal serum is based on pre-analysis conversion of bilirubin monosugar and disugar conjugates to the corresponding methyl esters by alkaline methanolysis. Here, extracted unconjugated bilirubin, bilirubin monomethyl esters, bilirubin dimethyl ester, and internal standard are separated on a reversed-phase column within 15 min, detected in the effluent at 436 nm, and quantified from their peak areas. Carotenoids do not interfere. Within-day and day-to-day CVs range from 5 to 13%. The smallest concentrations of monoconjugated and diconjugated pigments that are detectable and measurable are about 10 and 20 nmol/L, respectively. Such data are given for sera from 43 healthy adults. Total bilirubin concentrations in serum tended to be lower in women than in men, but the relative amounts of the various bilirubin fractions in sera from men and women were comparable. Analysis of ethyl anthranilate azoderivatives from serum permitted identification of the bilirubin ester conjugates in normal serum as bilirubin 1-O-acyl glucuronides.

Latex immunoassay of retinol-binding protein.

Latex immunoassay, a sensitive method based on latex particle agglutination, is used here for the determination of retinol-binding protein in human biological fluids. The assay, similar to that described previously for beta 2-microglobulin (Clin. Chem. 27:832-837, 1981), consists of incubating the sample at 37 degrees C for 30 min with antibody-coated particles, then quantifying the resulting agglutination by particle-counting or turbidimetry. Latex particles coated with antibody are stabilized just before use by dispersing them in a solution of bovine serum albumin at pH 10. The standard curve ranges from 0.5 to 32 micrograms/L; recovery averages 102% in urine and 93.5% in serum; between- and within-assay CVs range from 5.1 to 11.7%. The correlation coefficients of latex immunoassay with rocket immunoelectrophoresis for analysis of retinol-binding protein in 26 urines and with radial immunodiffusion in 30 sera are 0.99 and 0.91, respectively. In healthy subjects, the mean urinary excretion of retinol-binding protein is 52.5 micrograms/g of creatinine (SD = 59.2 micrograms/g of creatinine; n = 150) and the concentration in serum averages 46 mg/L (SD = 10.4 mg/L, n = 22).