Journal of the International Federation of Clinical Chemistry最新文献

Two methods for the routine determination of blood hemoglobin oxygen affinity are described. Both methods use whole blood and do not require special equipment, tonometry, or special gas mixtures. The first method consists of a one-point determination of p 50, and requires only 200 muL to 400 muL of whole blood, therefore making it suitable for the pediatric population. The second method uses multiple points, thereby establishing both the shape and position of the hemoglobin oxygen equilibrium curve between 10 and 99% oxygen saturation. Interpretation of p 50 is discussed in relation to evaluation of patients with hemoglobinopathies and as a parameter in estimating availability of oxygen to the tissues.

The Stratus total triiodothyronine (T3) immunoassay is an automated fluorometric enzyme immunoassay that utilizes a mouse monoclonal anti-T3 antibody preimmobilized onto glass fiber paper. The rate of formation of the enzyme product, as measured by front surface fluorometry, is inversely proportional to Total T3 concentration in the sample. The authors evaluated this method with respect to precision, sensitivity, interfering factors, and correlation with a radioimmunoassay. The overall, between-run, and within-run precision of the assay measured at three concentration levels for a total of 60 determinations each using immunoassay control materials, ranged from 2.5% to 14.3%. A total of 200 specimens, including 40 classified as hyperthyroid, and 38 classified as hypothyroid were analyzed in duplicate by the Stratus (STR) system and by a commercially available radioimmunoassay method. The coefficient of correlation obtained was 0.97. Icteric, hemolyzed, azotemic, and lipemic samples were included in the comparison and do not appear to have any interfering effect on the assay. The range of the assay is from 0.8 to 12 nmol/L. In summary, the Stratus Total T3 immunoassay offers the advantages of sensitivity, specificity, and automation with a throughput rate of 45 samples/h.

Autoantibodies directed against the intermediate filament proteins (IF) arise in a variety of disease states. The authors have investigated the binding of the IF to solid membrane supports in a dot blot format in an attempt to develop a simple procedure to detect antibodies (ab) to IF. Commercially obtained, purified IF were utilized. These were: vimentin (VIM), cytokeratin 8 (CYK), glial fibrillary acidic protein (GFA), desmin (DES), and the neurofilament triplet proteins (68, 160, and 200 KDa, respectively designated LMW, MMW, and HMW). Murine monoclonal antibody (mAb) probes were used to detect the presence and immunoreactivity of IF. The mAb were visualized with HRP-anti-mouse conjugates using alpha-chloronaphthol/H 2O 2 as substrate. The membranes studied were nitrocellulose (NC), and two of modified nylon. Nitrocellulose provided the most reproducible binding; no advantage was found to ensue from the use of the other membranes with regard either to quantitative binding or improved capping. Among the IF studied, VIM, GFA, LMW, MMW, and HMW bound well to NC; optimal mass/dot was 1 mug. Filtered, non-fat dry milk is a better capping agent than either albumin or fetal calf serum, but interferes with ab binding to GFA. Binding of CYK and DES is weak at neutral pH. Standard densitometric techniques provide the possibility of quantitation. We conclude that dot and slot blot assays may be practical methods to detect ab to IF antigens.

Hydrodynamic electrochemical techniques such as liquid chromatography and flow injection analysis with electrochemical detection are very effective for the rapid determination of the enzyme-generated product in enzyme immunoassays. The authors have used this detection method in various assay formats using both alkaline phosphatase and glucose-6-phosphate dehydrogenase as labels. Assays for digoxin will be used illustratively. Recently, the authors have used 70 mL microcapillary hematocrit tubes as the immunoassay reaction vessel and alkaline phosphatase as the labeling enzyme. The assay, complete in 30 min, had a detection limit of 5,6 x 10 -20 moles of IgG in serum. The linear range was four orders of magnitude. This low detection limit is due to a combination of the favorable geometry of the reaction vessel and the suppression of nonspecific adsorption by the addition of ion-pairing blocking agents. Even lower detectable amounts should be achievable with smaller reaction vessels. The capability for detecting such small amounts of analyte is potentially useful for the analysis of extremely small samples such as single cells and blood samples from premature infants.

Latex agglutination tests were invented in 1957. Thirty years later, new tests are still being devised and applied to new analytes. Reproducibility and readability continue to improve. Qualitative tests have now evolved to quantitative particle immunoassays: agglutination is detected by spectrophotometers or nephelometers, in tubes or 96-well plates. These same particles are now also being used in particle capture ELIST and ELISA (enzyme linked immunosorbent tests and assays) where particles are caught upon a filter and act as supports for sandwich tests (those "+/-" or "blue-dot" tests). These also can be quantified, as in the Abbott IM x assay system. Dyed microspheres now function as the color tags in over-the-counter sandwich-type pregnancy tests. In the future, results from assays using this technology could be read on reflectometers (strip readers). Currently, magnetic particles are used in solid phase radioimmunoassays and DNA probes.

This document provides guidelines in the terminology, methodology, and in the interpretation of data obtained from the use of skin (transcutaneous) p O2 and p CO2 electrodes. The transcutaneous technique has found special application for newborn infants. The causes of analytical bias with respect to arterial blood gas values and imprecision obtained with transcutaneous p O2 and p CO2 electrodes are reviewed. Electrode temperatures above 44 degrees C should not be used routinely, and, at a measuring temperature of 44 degrees C, the measuring site should be changed at least every 4 h to avoid skin burning.