Comparison of whole-blood tacrolimus concentrations measured by different immunoassay systems.

INTRODUCTION: Different measured values for tacrolimus were obtained with different automated immunoassays. We aimed to examine the differences in the blood tacrolimus concentrations measured by the major immunoassay systems commercially available in Japan. METHODS: Whole-blood samples from 118 patients were assayed by 3 commercial assays: chemiluminescent enzyme immunoassay (CLIA), affinity column-mediated immunoassay (ACMIA), and enzyme-multiplied immunoassay technique (EMIT). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for reference. KEY FINDINGS: The correlation coefficient of immunoassay vs LC-MS/MS was excellent for ACMIA (.83) and CLIA (.81) and good for EMIT (.71). The mean error was negative for ACMIA and positive for CLIA and EMIT. The mean absolute error and root-mean-square error were almost the same for ACMIA and CLIA and lower than those for EMIT. CONCLUSIONS: The ACMIA and CLIA yield considerably better results than the EMIT for monitoring blood tacrolimus concentrations.

Antineutrophil cytoplasmic antibodies (ANCA) testing: detection methods and clinical application.

Antineutrophil cytoplasmic antibodies (ANCA) are considered the diagnostic biomarker of some necrotising vasculitis such as granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and, to a lesser extent, eosinophilic granulomatosis with polyangiitis (EGPA). According to the current recommendations, combining indirect immunofluorescence and proteinase 3 (PR3) and myeloperoxidase (MPO) antigen specific immunometric assays, in the proper clinical setting, assures the best diagnostic specificity. When such conditions are satisfied, ANCA are detected in up to 90% of patients with active generalised GPA and MPA and in about 40% of patients with EGPA. Cytoplasmic ANCA (C-ANCA) with specificity for PR3 are usually found in patients with GPA whereas perinuclear ANCA (P-ANCA) in patients with MPA and EGPA. However, ANCA antigen specificity is more closely associated with disease phenotype and prognosis than clinical diagnosis. The clinical value of serial ANCA testing in monitoring disease activity is still debated. Recently, new promising developments in methodology and techniques (computer-based image analysis of immunofluorescence patterns, novel generation of PR3-/MPO-ANCA immunometric assays and multiplex technology) have been proposed but studies comparing the performances of the different assays are scarce.

The mystifying nomenclature of cardiac troponin immunoassays.

The laboratory assessment of cardiospecific troponins(s) represents the cornerstone for the diagnosis of acute coronary syndrome (ACS). Although troponin immunoassays are classified according to either analytical imprecision or percentage of measurable values in a presumably healthy population, it is rather clear that the nomenclature of commercial methods according to these systems of classification carries several drawbacks. The leading problems in classification according to imprecision are represented by the arbitrarity of optimal imprecision threshold, the uncertain correspondence between analytical performance and clinical outcomes and the improper use of terms, which has also been magnified by the lack of specific focus on this topic by regulating bodies such as the US Food and Drug Administration (FDA) and the European Union. Additional issues emerging from classification according to percentage of measurable values include the characterization of healthy population, the variation of values according to age, gender and race, as well as the influence of comorbidities. Considering that what really matters from a clinical standpoint is the clinical performance of the assay rather than the claimed analytical characteristics, it seems reasonable at this point in time to introduce a paradigm shift and gradually abandon the former analytical classification in favour of a different approach, preferable based on clinical outcomes.

Immunology and microbiology devices; reclassification of the herpes simplex virus serological assay device. Final rule.

The Food and Drug Administration (FDA) is amending the special controls for the herpes simplex virus (HSV) serological assay device type, which is classified as class II (special controls). These device types are devices that consist of antigens and antisera used in various serological tests to identify antibodies to herpes simplex virus in serum, and the devices that consist of herpes simplex virus antisera conjugated with a fluorescent dye (immunofluorescent assays) used to identify herpes simplex virus directly from clinical specimens or tissue culture isolates derived from clinical specimens.

Medical devices; immunology and microbiology devices; classification of ovarian adnexal mass assessment score test system. Final rule.

The Food and Drug Administration (FDA) is classifying the ovarian adnexal mass assessment score test system into class II (special controls). The special control that will apply to these devices is the guidance document entitled "Guidance for Industry and FDA Staff; Class II Special Controls Guidance Document: Ovarian Adnexal Mass Assessment Score Test System." The Agency is classifying these devices into class II (special controls) because special controls, in addition to general controls, will provide a reasonable assurance of safety and effectiveness of these devices and there is sufficient information to establish special controls. Elsewhere in this issue of the Federal Register, FDA is announcing the availability of a guidance document that will serve as the special control for these devices

Evaluation of current methods for the measurement of serum anti double-stranded DNA antibodies.

Autoantibodies to double-stranded DNA (dsDNA) are, by definition, serological markers of systemic lupus erythematosus. However, the clinical value of anti-dsDNA antibodies largely depends on the assay principle and analytical variables of the methods used to quantitate and immunologically characterize them. In the present article, an overview of current methods for anti-dsDNA antibody detection is presented, together with a look at the future trends in technologies newly employed in this field.

Medical devices; immunology and microbiology devices; classification of quality control material for cystic fibrosis nucleic acid assays. Final rule.

The Food and Drug Administration (FDA) is classifying quality control material for cystic fibrosis nucleic acid assays into class II (special controls). The special control that will apply to the device is the guidance document entitled "Class II Special Controls Guidance Document: Quality Control Material for Cystic Fibrosis Nucleic Acid Assays." The agency is classifying the device into class II (special controls) in order to provide a reasonable assurance of safety and effectiveness of the device. Elsewhere in this issue of the Federal Register, FDA is announcing the availability of the guidance document that will serve as the special control for this device.

Medical devices; immunology and microbiology devices; classification of fecal calprotectin immunological test systems. Final rule.

The Food and Drug Administration (FDA) is classifying fecal calprotectin immunological test systems into class II (special controls). The special control that will apply to these devices is the guidance document entitled, "Class II Special Controls Guidance Document: Fecal Calprotectin Immunological Test Systems." The agency is classifying these devices into class II (special controls) in order to provide a reasonable assurance of safety and effectiveness of these devices. Elsewhere in this issue of the Federal Register, FDA is announcing the availability of a guidance document that will serve as the special control for these devices.

[TSH-receptor antibodies: immunoanalytical characteristics]. / Les anticorps anti-récepteur de la TSH : caractéristiques immunoanalytiques.

Besides the main biochemical characteristics of anti TSH-receptor antibodies, this paper points out the optimal conditions for their assays and the interpretation of results.

Immunochemical assays in the clinical laboratory.

State-of-the-art immunochemical assays and future directions in this science are reviewed. Immunochemical assays may be categorized as follows: Type I, or single-site noncompetitive immunoassays; type II, two-site noncompetitive immunoassays; type III, homogenous competitive immunoassays; and type IV, nonhomogenous competitive immunoassay. Assay systems use radionuclides, enzymes, fluorescence, chemiluminescence, and particles as reporters in the tests. Radionuclides will continue to decline in importance as other systems are refined. More sensitive reporters and clever multi-analyte systems will continue to be developed.

Immunoassay standardization.

Assays employed in the biological sciences fall into two categories, which may be respectively termed "comparative" (or "functionally-specific") and "analytical" (or "structurally-specific"). The former are intended to compare the relative effects of substances, or mixtures of substances--not necessarily of identical chemical structure--on a biological system (e.g. whole animal, tissue, cell, etc). Results are represented by units of effect (i.e. they are not units of "amount" of the substance(s) measured), and differ depending on the biological system used. Such assays cannot be "standardised" by the use of a calibrant. In contrast, analytical assays are intended to measure the number of molecules (or mass) of a single substance of unique chemical structure in a test sample, and cannot legitimately be employed to measure mixtures of substances of different structure. Results are represented by units of molecular number or mass, and should be identical for any test sample irrespective of the assay system used. Immunoassays generally fall into this category. Insofar as the antigenic substances present in standards or test samples are dissimilar and/or molecularly heterogeneous, an immunoassay is invalid, and the results it yields have no universal significance. Attempts to standardize "analytically-invalid" immunoassays inevitably fail. Many substances of biological interest (e.g. TSH)--initially defined in terms of their biological function--have subsequently been shown to be molecularly heterogenous. Problems thus arise in the standardization of immunoassays used for their measurement, reflecting the fact that the measurement of a mixture of substances of differing molecular structure (and function) is a meaningless concept. It is thus impossible to "measure TSH"; it is only possible to measure the effect TSH exerts in a particularly assay system. The only long-term solution to this problem is the development of assay systems measuring individual components of such heterogenous mixtures.

Medical devices; immunology and microbiology devices; classification of the beta-glucan serological assay. Final rule.

The Food and Drug Administration (FDA) is classifying the beta-glucan serological reagent device into class II (special controls). The special control that will apply to the device is the guidance document entitled "Class II Special Controls Guidance Document: Serological Assays for the Detection of Beta-Glucan." The agency is taking this action in response to a petition submitted under the Federal Food, Drug, and Cosmetic Act (the act) as amended by the Medical Device Amendments of 1976 (the 1976 amendments), the Safe Medical Devices Act of 1990, the Food and Drug Administration Modernization Act of 1997, and the Medical Device User Fee and Modernization Act of 2002. The agency is classifying the device into class II (special controls) in order to provide a reasonable assurance of safety and effectiveness of the device. Elsewhere in this issue of the Federal Register, FDA is publishing a notice of availability of a guidance document that is the special control for this device.

Progesterone determination in equine plasma using different immunoassays.

Several assay systems (3H radioimmunoassay (RIA) with and without extraction; microplate enzyme-linked immunoassay (ELISA); qualitative ELISA (tube test)] were used to measure plasma progesterone concentration in mare plasma. The direct RIA showed a close correlation (R = 0.94) with the extraction RIA. The direct RIA and the microplate ELISA were compared in two different studies. In the first study 1155 samples of postpartum mares were used for progesterone determination with both assays. The ELISA resulted in more elevated values both in oestrus and dioestrus (0.19+/-0.3 and 2.44+/-3.62 nmol/l for oestrus, n = 436, and 8.94+/-4.29 and 27.88+/-18.34 nmol/l for dioestrus, N = 719, for the RIA and ELISA, respectively, R = 0.71). The evaluation of individual progesterone profiles has revealed that the microplate ELISA detects the time of ovulation at the same time as it is determined by the RIA and clinical examination. The sensitivity and specificity were calculated for different progesterone threshold values. In the second study including 7 non-pregnant, cycling mares the progesterone concentration of 240 samples was determined by both assays. Basal values (Day 0) obtained with the ELISA were higher (1.57 nmol/l) than those of the RIA (0.2 nmol/l). Both curves reached the same maximum concentration (12.11 and 12.45 nmol/l) 5 days after ovulation. The correlation between the RIA and ELISA values was high (R = 0.90). The tube test was compared to the microplate ELISA as reference using 576 plasma samples of 34 non-pregnant, non-cycling mares included in an ovulation induction study. Of these samples 118 had higher and 458 had lower values than 3.18 nmol/l. In most cases the tube test was in complete agreement with the microplate ELISA. The sensitivity, specificity, + predictive and - predictive values for the tube test were 79.7%, 95.4%, 81.7% and 94.8%, respectively.

[Progress in immunological methods of drug quantitation in clinical laboratory].

Progress in immunological methods of drug quantitation in the clinical laboratory was discussed from three different view points, (1) Immunoassay techniques: (a) Kinds of drug to be tested, (b) Classification of tests, (c) Utilization rate of the tests and (d) Non-instrumental technique, (2) Therapeutic monitoring: (a) An example of digoxin monitoring and (b) Problems related to creatinine clearance in digoxin monitoring, (3) Development in future: (a) Identification and characterization of endogenous digoxin-like substance and (b) Application of optical isomer of drug to laboratory test.

[Various types of immunoassay].

Five types of immunoassay, enzyme immunoassay (EIA), radioimmunoassay (RIA), fluoroimmunoassay (FIA), chemiluminescent immunoassay (CLIA) and counting immunoassay (CIA), are generally used. Radioimmunoassay was first developed but it needs specific facilities and the half life of radioisotope is not long. Enzyme immunoassay is at present most popular in Japan. The goal of development of immunoassay is improvement of sensitivity and automation. In order to improve sensitivity of an assay, immunoenzymometric assay (IEMA), which is a non-competitive method, was developed and fluorescent materials and chemiluminescent materials are used for the detection of enzyme activity. Automation of immunoenzymometric assay could be done with solid phase antibody method.

Validation of the Dual-path Platform chromatographic immunoassay (DPP® CVL rapid test) for the serodiagnosis of canine visceral leishmaniasis

BACKGROUND Visceral leishmaniasis is a major public health challenge in South America, and dogs are its main urban reservoir. OBJECTIVE Validation of the canine Dual-path Platform immunoassay for canine visceral leishmaniasis (DPP® CVL) for a sample set composed of 1446 dogs from different Brazilian endemic areas. METHODS A well-defined reference standard by means of parasitological culture, immunohistochemistry, and histopathology was used. Animals were classified as asymptomatic, oligosymptomatic, or symptomatic. Sensitivity and specificity were assessed as a single set and in clinical groups. A reproducibility assessment of the tests was conducted using the Kappa (κ) index at three different laboratories (A, B, and C). FINDINGS Overall, 89% sensitivity and 70% specificity were obtained for the entire sample set. Analysis of the clinical groups showed a gradual decrease in the sensitivity and an increase in the specificity with the reduction of clinical signs in the dogs that were assessed, reaching a sensitivity of 75% (42.8-94.5%) among asymptomatic dogs and lower specificity of 56% (46.2-66.3%) among symptomatic dogs. Inter-laboratory agreement was substantial (κAB= 0.778; κAC= 0.645; κCB= 0.711). MAIN CONCLUSIONS The test performance is somewhat dependent on canine symptomatology, but such influence was less evident than in previous studies. Favourable results for sensitivity and specificity can be obtained even in asymptomatic animals; however, caution is needed in these evaluations, and the results suggest that the immunochromatographic test may be further improved for better investigation in asymptomatic dogs. The results obtained confirm the usefulness of DPP® CVL for application in serological surveys.

Basic features of biomedical assays.

All biomedical assays have certain aspects in common, the most striking of which is that they generally involve protein-binding. Ligand-ligator interactions and the resulting response form the basis of most assays. This paper reviews the advantages and limitations of different types of assays ranging from long-term bioassays to in vitro assays using cell-free components. Consideration of these aspects helps in the understanding of the different assays, selection of appropriate assays for different applications, and the better interpretation of assay results. Clinical chemists, hematologists, endocrinologists, immunologists, and scientists from other disciplines have each developed their own measurement methods and units. This paper seeks to identify those aspects and principles common to assays in all such disciplines, concentrating on protein-binding systems. Understanding what and how different assays measure may clarify why different assay methods often give different results.