Comparison of seven commercial kits for detection of antibodies toBorrelia burgdorferi

Five enzyme immunoassay (EIA) and two Western blot (WB) commercial kits were compared for their ability to detect antibodies toBorrelia burgdorferi. The panel of 53 test sera consisted of 25 sera positive for antibodies toBorrelia burgdorferi, 15 sera negative for such antibodies, 5 sera reactive in serologic tests for syphilis, and 8 sera containing antinuclear antibodies and/or rheumatoid factor. The rate of agreement with reference results was 93 %, 90 %, 90 % and 88 % for EIA kits from Diamedix, Cambridge Biotech, Mardx and Sigma respectively. The sensitivity and specificity was 84 % and 100 % respectively for Cambridge Biotech, 76 % and 94 % for Diamedix, 68 % and 83 % for Mardx, and 68 % and 83 % for Sigma. The three confirmatory tests, Cambridge Biotech WB, General Biometrics P39 EIA and Mardx WB, demonstrated 75 %, 60 % and 63 % agreement respectively. The sensitivity and specificity was 52 % and 100 % respectively for Cambridge Biotech WB, 24 % and 100 % for General Biometrics P39 EIA, and 44 % and 100 % for Mardx WB. The results demonstrate the variable performance of commercial serologic kits for detection of antibodies toBorrelia burgdorferi. WB appears to be a better confirmatory test than the single protein EIA.     

Relevance of anti-nucleosome antibodies detected by enzyme-based immunoassays in lupus diagnosis. Comparative analysis of four commercial kits

Among the biological assays used for the diagnosis of systemic lupus erythematosus (SLE), the detection of anti-double strand DNA antibodies (dsDNA Ab) is regarded as highly specific. However this biological parameter is negative among 20 to 40% of patients. Recent studies have revealed potential interest of the anti-nucleosome antibodies in the diagnosis of the lupus, in particular when any anti-dsDNA antibody activity could be detected. We selected 80 sera in order to evaluate four commercial anti-nucleosome enzyme-based immunoassays (EIA) kits. Their sensitivity and specificity values were compared with those obtained by the detection of anti-dsDNA Ab, carried out with both a Farr assay and two EIA kits. No anti-nucleosome EIA kits reached performances of the Farr assay for the diagnosis of lupus. On the other hand, our results show an higher diagnostic value for some anti-nucleosome EIA kits compared with 2 anti-dsDNA EIA kits. Apart from SLE, anti-nucleosome antibodies can be observed in others auto-immune diseases, in particular Sj?gren's syndromes, the primary antiphospholipid syndrome, the systemic sclerosis and the mixed connective tissue disease. Compared results of the four anti-nucleosome EIA kits highlight many discordances. These variations, testifying to the absence of standardization for this new parameter, must encourage with a careful interpretation of results, according to the clinical context.     

Multi-laboratory comparison of eight commercially availableHelicobacter pylori serology kits

The performance of eight commercially available EIA kits in detecting antibody toHelicobacter pylori was evaluated by a panel of 17 laboratories using serum from 59 patients selected from endoscopy clinics in Belgium, Ireland, Italy, the Netherlands and Switzerland. Each laboratory received a randomly numbered set of sera and was ignorant of the culture results of the patients. The performance of the kits was assessed in terms of diagnostic accuracy compared to culture (measured by sensitivity and specificity), the interlaboratory variability in diagnostic accuracy and the number of laboratories that experienced problems in using the kits. Grey zone results, which are routinely used to highlight the uncertain interpretation of results that lie near the cut-off point between positive and negative diagnoses, were accounted for in the analysis. Laboratories experienced practical problems in using some kits, whilst other kits were found to have high inter-laboratory variation or low diagnostic accuracy. There was no single kit that performed better on every criterion than the others. The Orion kit was a good all-round performer, whilst the Roche kit was excellent at detecting positive results, although it had a slightly raised false-positive rate.     

Evaluation of three commercial enzyme immunoassay kits for detecting faecal Clostridium difficile toxins.

The detection of faecal cytotoxicity using tissue culture was compared with three commercial Clostridium difficile enzyme immunoassay (EIA) kits; Premier C difficile toxin A (Meridian Diagnostic, Inc.); CD-TOX C difficile toxin A (Porton Cambridge); and Cytoclone A+B EIA (Cambridge Biotech Corporation). Of 160 faecal samples examined by all four methods, 52 (32.5%) were cytotoxic, 44 (27.5%) were positive by Premier, 48 (30%) by CD-TOX EIA, and 50 (31.3%) with Cytoclone. When compared with detection of cytotoxicity by tissue culture assay, the following performance indices were obtained: Premier, sensitivity 84.1%, specificity 99.1%, positive predictive value (PPV) 97.8%, negative predictive value (NPV) 93%; CD-TOX, sensitivity 92.3%, specificity 88.0%, PPV 78.7%, NPV 95.9%; Cytoclone, sensitivity 96.2%, specificity 93.5%, PPV 87.7%, NPV 98.1%. EIA results were available within three hours, whereas the results of the cytotoxin assay were available after 24-48 hours. All three kits provided satisfactory results and, although relatively expensive, all could be used in the laboratory effectively to screen for diarrhoeal disease associated with C difficile.     

Rapid detection of respiratory syncytial virus in nasopharyngeal aspirates by a commercial enzyme immunoassay.

A commercial enzyme immunoassay (EIA) for the rapid detection of respiratory syncytial virus (RSV) in respiratory secretions was evaluated by comparison with both virus isolation in HEp-2 cells and indirect immunofluorescence (IFA) staining of exfoliated respiratory cells. Initial examination of 80 nasopharyngeal aspirates collected from infants with acute respiratory illness showed that the RSV EIA was positive for 21 of 24 specimens positive by virus isolation or IFA (87.5% sensitivity) and negative for 53 of 56 specimens negative by virus isolation and IFA (95% specificity). The EIA appears to be an acceptable and more rapid test than virus isolation for the detection of RSV, especially for laboratories in which prompt inoculation of specimens is not always possible. IFA staining with commercial bovine anti-RSV serum was found to be the most sensitive and rapid test for the detection of RSV. However, three of four specimens positive by IFA and negative by virus isolation were not cultured under optimal conditions. In addition, the IFA test requires a highly trained technologist to interpret the staining results.     

HIV抗体酶联免疫诊断试剂检测不同基因型抗体的研究

目的 分析不同HIV抗体酶联免疫诊断试剂对检测HIV不同基因型抗体的情况。方法 对不同地区的20份HIV抗体阳性样品中HIV核酸进行扩增，对PCR产物进行测序并进行基因型别分析。用不同试剂对系列稀释的不同基因型样品进行检测。结果 20份样品均为HIV RNA阳性，其中9份样品为HIV B亚型，9份样品为：HIV C或BC重组，2份为HIVAE重组。不同试剂对HIV不同基因型抗体的检测灵敏度无明显差异。结论 我国主要的商业化HIV抗体诊断试剂产品检测不同基因型抗体的能力无明显差异。     

Evaluation of two commercial human T-cell lymphotropic virus western blot (immunoblot) kits with problem specimens.

We evaluated two commercial human T-cell lymphotropic virus (HTLV) Western blot (WB; immunoblot) kits, Cambridge Biotech Corp. (CBC) and Diagnostic Biotechnology Ltd. (DBL). Both methods employ HTLV type I (HTLV-I) viral lysate and rgp21. The DBL WB kit also distinguishes between HTLV-I and HTLV-II antibodies, using an HTLV-I-specific and an HTLV-II-specific recombinant. Fifty weakly reactive HTLV-II-positive plasma specimens which were falsely negative with the Abbott enzyme immunoassay (EIA) and 50 Ortho EIA false-positive samples were selected to determine sensitivity and specificity. The sensitivities of the CBC and the DBL WB kits were 90 and 68%, respectively. All positive samples reacted with rgp21 in both kits, but some did not display core bands. Five samples were typed as HTLV-I and four were typed as dual infection by the DBL WB kit. The specificities of the CBC and DBL kits were 48 and 70%, respectively. The most prevalent WB reaction with the negative samples was with the core protein, p19, followed by p24 and p28 for CBC and rgp21 and p28 for DBL. DBL had two false-positive interpretations, and CBC had none, rgp21 was the most sensitive antigen in both kits for the weakly reactive HTLV-II samples. If all samples not reacting with this protein were interpreted as WB negative, regardless of other bands, the specificity would improve to 90% for CBC and 86% for DBL.     

Evaluation of nine immunoassay kits (enzyme immunoassay and direct fluorescence) for detection of Giardia lamblia and Cryptosporidium parvum in human fecal specimens.

It is well known that Giardia lamblia and Cryptosporidium parvum can cause severe symptoms in humans, particularly those who are immunologically compromised. Immunoassay procedures offer both increased sensitivity and specificity compared to conventional staining methods. These reagents are also helpful when screening large numbers of patients, particularly in an outbreak situation or when screening patients with minimal symptoms. The data obtained by using 9 diagnostic kits were compared: direct fluorescent-antibody assay (DFA) kits (TechLab Giardia/Crypto IF kit, TechLab Crypto IF kit, and Meridian Merifluor Cryptosporidium/Giardia) and enzyme immunoassay (EIA) kits (Alexon ProSpecT Giardia EZ Microplate Assay, Alexon ProSpecT Cryptosporidium Microplate Assay, Cambridge Giardia lamblia Antigen Microwell ELISA, Meridian Premier Giardia lamblia, Meridian Premier Cryptosporidium, TechLab Giardia CELISA, Trend Giardia lamblia EIA). The test with the Meridian Merifluor Cryptosporidium/Giardia kit was used as the reference method. In various combinations, 60 specimens positive for Giardia, 60 specimens positive for Cryptosporidium, 40 specimens positive for a Giardia-Cryptosporidium mix, and 50 negative fecal specimens were tested. Different species (nine protozoa, three coccidia, one microsporidium, five nematodes, three cestodes, and one trematode) were included in the negative specimens. The sensitivity of EIA for Giardia ranged from 94% (Alexon) to 99% (Trend and Cambridge); the specificity was 100% with all EIA kits tested. The sensitivity of EIA for Cryptosporidium ranged from 98% (Alexon) to 99% (Meridian Premier); specificities were 100%. All DFA results were in agreement, with 100% sensitivity and specificity; however, the TechLab reagents resulted in fluorescence intensity that was generally one level below that seen with the reagents used in the reference method. In addition to sensitivity and specificity, factors such as cost, simplicity, ease of interpretation of results (color, intensity of fluorescence), equipment, available personnel, and number of tests ordered are also important considerations prior to kit selection.     

Anti-neutrophil cytoplasmic autoantibody-associated glomerulonephritis and vasculitis.

Anti-neutrophil cytoplasmic autoantibodies (ANCA) react with constituents of neutrophil primary granules and monocyte lysosomes. Indirect immunofluorescence microscopy using alcohol-fixed neutrophils demonstrates two ANCA types: one causing cytoplasmic staining (C-ANCA), and a second causing artifactual perinuclear staining (P-ANCA) that frequently has specificity for myeloperoxidase. Using indirect immunofluorescence microscopy (IIFM) and enzyme immunoassays (EIA), sera from over 300 patients with renal disease, with and without systemic vasculitis, were analyzed. Of 76 patients with pauci-immune glomerulonephritis with crescents or necrosis, 87% had ANCA by IIFM (38% of C-ANCA type, 49% of P-ANCA type), and 78% had ANCA by EIA. Of 55 patients with nonlupus immune complex-mediated glomerulonephritis, only 11% had ANCA by IIFM and 5% had ANCA by EIA. Of 24 patients with anti-GBM antibody-mediated glomerulonephritis, none had ANCA. Renal and extrarenal lesions were studied in 81 patients with ANCA-associated glomerulonephritis. These patients formed a pathologic continuum ranging from renal-limited to widespread systemic vascular injury, including patients with primary crescentic glomerulonephritis, Wegener's granulomatosis, and polyarteritis nodosa. In ANCA-positive patients the frequency of C-ANCA and P-ANCA correlated with disease distribution. P-ANCA was most frequent with renal-limited disease and C-ANCA was most frequent when there was lung and sinus involvement. It is proposed that ANCA are not only useful diagnostic markers, but may also be directly involved in a novel pathogenetic mechanism that is a frequent cause of crescentic glomerulonephritis and systemic necrotizing vasculitis.     

Evaluation of two commercially available anti human immunodeficiency virus antibody ELISA Kits using clinical samples

Laboratory diagnosis is the mainstay in the diagnosis of HIV infection in an individual. The wide range of diagnostic kits available, for the detection of anti HIV antibodies, makes it mandatory that the kits are evaluated before they are made available in the market. We evaluated the performance of a Microlisa HIV kit (J. Mitra & Co.) using a panel of HIV reactive and non reactive clinical specimens. The sensitivity and specificity of the kit were found to be 100% as compared to the UBI HIV 1/2 EIA kit. The ease of testing, the assay characteristics including efficiency of the Microlisa favour its use by laboratories as a primary screen for HIV infection.     

Five commercial enzyme linked immunosorbent assay kits for toxoplasma specific IgM antibody.

Five commercially available enzyme linked immunosorbent assay (ELISA) kits for the detection of specific IgM against Toxoplasma gondii were evaluated in a three centre study and results compared with those of the Public Health Laboratory Service ELISA for Toxoplasma IgM (PHL IgM ELISA). Fifty selected sera were tested by all the methods (Toxo-M, Captia Toxo-M EIA, Toxo Enz M EIA, Toxonostika IgM EIA, Sopazyme Toxo IgM EIA) at the three reference centres in England and Wales and 177 routine sera by all the methods in one or other of the centres. Ten of the 50 selected sera contained autoimmune antibodies but no specific IgM and 29 had toxoplasma specific IgM detectable by the PHL IgM ELISA. The kits were assessed for their specificity and sensitivity compared with the PHL IgM ELISA, and the percentage coefficient of variation for binding to the solid phases was determined. They were also rated subjectively by the staff performing the assays and an overall impression of each kit was gained by allocating scores of several criteria. There was quite close agreement among the results obtained with all five commercial assays and the PHL IgM ELISA, although some of the sera pre-selected as being potentially problematic showed the limitations of some of the assays.     

Evaluation of EIA kits for the detection of HIV antibodies

We compared four commercially available enzyme immunoassay (EIA) kits for the detection of HIV antibodies using immunoblot analysis as a confirmatory test. The kits gave satisfactory results as far as sensitivity and specificity are concerned as required for the use in the laboratories of blood banks. For the sera of patients on haemodialysis, haemophiliacs, patients "under observation" for AIDS and homosexuals the results obtained by Behring and Organon kits were less satisfactory, as the number of false positive results was much higher than with kits produced by Genetic and Wellcome. The frequency of false negative results was small in the tests using Organon and Genetic kits, while using Behring and Wellcome kits no false negative results were found.     

Selective detection of autoimmune antibodies to single- and double-stranded DNA by enzyme immunoassay

Presence in serum of anti-double-stranded deoxyribonucleic acid antibodies (anti-dsDNA) is one of the diagnostic criteria for systemic lupus erythematosus. Anti-single stranded DNA antibodies (anti-ssDNA) also occur, but their clinical significance is unclear. Use of enzyme immunoassay (EIA) kits that are specific for anti-dsDNA is desirable but problematic, since preparation of dsDNA of high integrity is difficult (ie, regions of ssDNA may persist). This study evaluated an EIA kit that uses low Mw plasmid/bacteriophage DNA as a nucleic acid source. Anti-dsDNA results were compared to results obtained by an anti-ssDNA EIA and an immunofluorescent assay (IFA) that uses Crithidia luciliae (specific for anti-dsDNA). Consecutive serum samples (n=139, 88% female) submitted to the clinical laboratory for anti-dsDNA analysis were evaluated. EIA precision was determined at three levels. Intra-assay precision [mean +/- SD (CV)] for anti-dsDNA: 36 +/- 3.5 IU/ml (9.8%); 98 +/- 4.4 (4.5%); and 245 +/- 5.8 (2.4%); and anti-ssDNA. 40 +/- 1.4 U/ml (3.5%); 190 +/- 4.8 (2.5%); and 283 +/- 10.3 (3.7%) (n=8). Inter-assay precision for anti-dsDNA: 36 +/- 6.3 IU/ml (17.5%); 90 +/- 5.9 (6.6%); and 207 +/- 20.9 (10.1%); and anti-ssDNA: 48 +/- 8.2 U/ml (17.0%); 193 +/- 12.7 (6.6%); and 263 +/- 21.5 (8.2%) (n=8). Linearity was assessed with (a) high dsDNA/high ssDNA and (b) low dsDNA/high ssDNA samples (no high dsDNA/low ssDNA samples were identified). Linearity (>200 IU/ml) was found for both sample types with a correlation coefficient (r) of 0.995-0.999. Anti-dsDNA immunoreactivity was not apparent with the low dsDNA/high ssDNA sample. More patients were positive for anti-ssDNA (54%), compared to anti-dsDNA (17%). IFA confirmation (Crithidia) indicated a relative sensitivity and specificity of 94.1% and 93.4% for the anti-dsDNA EIA. IFA positivity correlated with increased anti-dsDNA level: 20% (30-60 IU/ml); 70% (61-200 IU/ml); and 89% (>200 IU/ml). Of specimens that were anti-ssDNA positive and anti-dsDNA negative (n=51), only one was IFA positive. When IFA was compared to an anti-dsDNA EIA kit that used high Mw calf thymus DNA, lower relative specificity (88.2%) and sensitivity (72.6%) was obtained. Anti-ssDNA was found in many false positive specimens (87%).     

Evidence-Based Diagnosis of Toxoplasma Infection

 The aim of this study was to compare the performance of one in-house and four commercially available toxoplasma assays with the Sabin-Feldman dye test. One hundred fifty-seven routine sera and 20 potentially cross-reactive sera were tested blindly using four commercial assays: Abbott AxSym IgG (Abbott Laboratories, UK), Captia Select Toxo-G (Trinity Biotech, UK), Toxreagent 'Eiken' (Eiken Chemical, Japan) and Toxolatex Fumouze (Fumouze Laboratoires, France); an in-house IgG and IgM enzyme immunoassay (EIA); and the gold standard Sabin-Feldman dye test. The sensitivity, specificity and the values using the formulae for numbers needed to diagnose (NND) and the cost per positive diagnosis (CPPD) were calculated for each assay. These formulae use the sensitivity and specificity of the assay to allow for evidence-based comparisons between assays. The NND values for the in-house IgG EIA, AxSym, Eiken and Fumouze latex kits were similar (1.21–1.24), whereas the Captia yielded the poorest value (1.33). The in-house EIA IgG had the lowest CPPD value (￡0.57/$0.91), and the Fumouze and Eiken latex kits had the lowest CPPD values for commercial assays (￡1.42/$2.27 and ￡1.81/$2.90, respectively). Both assays were simple and straightforward to use. Specialist laboratories should opt to use in-house assays, as they were most cost-effective. Although nonspecialist laboratories could use commercial assays, specimens from immunocompromised patients and patients with ocular disease should be forwarded to specialist laboratories without prior testing.     

Identifying human herpesvirus 8 infection: performance characteristics of serologic assays

Epidemiologic studies of infection with the oncogenic human herpesvirus 8 (HHV-8) depend on serologic methods to diagnose infection. However, optimal strategies for identifying HHV-8 infection remain undefined. We therefore evaluated four enzyme-linked immunoassays (EIAs) and one immunofluorescence assay (IFA) using sera from 87 individuals with the prototype HHV-8 disease, Kaposi's sarcoma (KS), and 210 participants in a hemophilia study (who were presumed not to be infected with HHV-8). Assays performed reasonably well in distinguishing between infected and uninfected persons, with receiver operator curve areas between 0.86 and 0.96. Nonetheless, IFA had only 86% sensitivity and 88% specificity, and no EIA simultaneously had sensitivity and specificity above 90% for any of the optical density (OD) cutpoints used to define seropositivity. Some assays were markedly less sensitive with diluted KS sera, suggesting that they poorly identify low-titer antibodies present in asymptomatic infection. We also developed a classification tree that categorized individuals as seropositive if they had OD > 2.00 on recombinant K8.1 protein EIA or if they had both K8.1 OD between 0.51 and 2.00 and positive IFA results; this strategy had between 80% and 90% sensitivity and 95% and 100% specificity. Overall, assays performed adequately for use in most epidemiologic investigations, but wider applications will require improved tests.     

Evaluation of HIV ELISA diagnostic kit developed at the Institute of Primate Research, Nairobi, Kenya

The first diagnostic kits utilizing the enzyme-linked immunosorbent assay (ELISA) technique were developed in mid-eighties, and since then, this technique has become an increasingly important tool for screening multiple samples of blood or serum for presence of antibodies to various infectious pathogens, especially human immunodeficiency virus (HIV) in blood banks. However, most of the commercial diagnostic kits currently available in the market are too expensive, hence not easily affordable in most Diagnostic Laboratories. We designed an ELISA kit for diagnosis of HIV and compared it with some of the commercial kits. We used blood samples from the blood bank at the National Public Health Laboratory Services (NPHLS) in Nairobi and from patients referred to the Kenya Medical Research Institute (KEMRI) for HIV screening. Two commercial kits were used, Wellcozyme HIV Recombinant kit and Recombigen (env & gag) HIV-1 EIA kit. Out of 1350 samples tested by Recombigen (env & gag) HIV-1 EIA kit, 419 (31.0% ) were positive while 421 (31.2% ) samples were positive by Wellcozyme HIV Recombinant kit. Our ELISA kit detected a total of 431 positive samples out of 1350 (31.9% ), which was almost identical to the results from the other kits. Our kit was nearly identical in terms of sensitivity and specificity to the other two commercial kits used in this study. Thus our ELISA system, which is much cheaper than the commercial kits currently available in the market, offers a more affordable system for routine HIV tests.     

A practical single sample dry latex agglutination test for Helicobacter pylori antibody detection.

Assessment of a single serum sample for Helicobacter pylori antibodies is frequently requested in routine diagnostic laboratories. Current enzyme linked immunosorbent assay (ELISA) kits are not ideal for testing small numbers of serum samples and some have low sensitivities, specificities or large grey zones. A panel of 90 serum samples from patients who had presented for routine upper endoscopy was used to compare three kits for the detection of H pylori antibodies: (1) Pyloriset Dry, total antibody latex agglutination, Orion Diagnostica, Espoo, Finland; (2) Pyloriset enzyme immunoassay (EIA), IgG ELISA, Orion; and (3) Hel-p, IgG ELISA, Amrad, Kew, Victoria, Australia. Diagnosis of H pylori positivity was made if culture results and either rapid urease test or histopathology were positive. The sensitivity, specificity, positive, and negative predictive value for each test was as follows: Orion: latex 93.3%, 95.6%, 95.5%, 93.3%, respectively; Orion: EIA-G 84.4%, 97.8%, 97.4%, 84.4%, respectively; and Amrad: EIA-G 100%, 88.9%, 90%, 100%, respectively. The latex test performed better than the EIAs with respect to sensitivity and specificity.     

Evaluation of five commercially available immunodiffusion kits for detection of Coccidioides immitis and Histoplasma capsulatum antibodies.

Five commercial test kits for the serodiagnosis of coccidioidomycosis and histoplasmosis based upon immunodiffusion were evaluated. The correlation of results with the test kits in the Clinical Laboratory varied from 71 to 100% for coccidioidomycosis. The correlation for coccidioidomycosis immunodiffusion testing varied from 57 to 83% when results from the test kits and the Mycology Research Laboratory were compared. Only 81% correlation was noted between the two laboratories when the same reference system was used. Results with the test kits for Histoplasma serodiagnosis and results from the Mycology Research Laboratory showed a correlation of 52 to 75%. There were no false-positive results with any system. All of the commercial kits were 100% specific for the diagnosis of both coccidioidomycosis and histoplasmosis, but the sensitivity of the immunodiffusion tests varied with the system used.     

Diagnostic accuracy of ELISA methods as an alternative screening test to indirect immunofluorescence for the detection of antinuclear antibodies. Evaluation of five commercial kits

Detection of antinuclear antibodies (ANA) is a fundamental laboratory test for diagnosing systemic autoimmune diseases. Currently, the method of choice is indirect immunofluorescence (IIF) on a HEp-2 cell substrate. The goal of this study was to evaluate the diagnostic accuracy of five commercially available enzyme immunoassay (EIA) kits for ANA detection and to verify the possibility of using them as an alternative to the IIF method. The study involved 1513 patients, 315 of whom were diagnosed with a systemic autoimmune disease and 1198 in whom an autoimmune disorder was excluded. For all sera, ANA detection was performed via IIF and with five different EIA kits. The results were evaluated in relation to clinical diagnosis and the presence of possible specific autoantibodies (anti-ENA or anti-dsDNA); lastly, they were compared with the results obtained using ANA-IIF as the method of reference. The positive rate of the ANA-IIF test in subjects with systemic autoimmune diseases was 92%, whereas in the five ANA-EIA kits there was broad diversity in terms of response, with positive rates ranging from 74 to 94%. All the EIA kits correctly detected the presence of antibodies (anti-dsDNA, anti-RNP, anti-Ro/SSA) responsible for homogeneous and speckled fluorescence pattern, but at the same time they showed substantial inaccuracy with the nucleolar pattern, with a mean sensitivity of approximately 50% in this case. Instead, there was a large kit-to-kit difference in terms of identification of anti-Scl70 and centromere patterns, for which sensitivities ranged between 45 and 91%, and between 49 and 100%, respectively. The results of the study demonstrate that the commercially available ANA-EIA kits show different levels of sensitivity and specificity. Some of them have a diagnostic accuracy that is comparable and, in some cases, even higher than the IIF method. Consequently, these could be used as an alternative screening test to IIE. However, others do not ensure acceptable results. Therefore, careful evaluation of the various kits on the market is advisable before including any of these methods in the clinical and diagnostic testing.     

Comparison of commercial enzyme immunoassay kits with plaque reduction neutralization test for detection of measles virus antibody.

Four commercially available enzyme immunoassay (EIA) kits were evaluated in comparison with the plaque reduction neutralization (PRN) test for detection of measles virus antibody. The EIA kits, Enzygnost (Behring), Diamedix, Vidas (bioMerieux Vitek), and Measlestat (Biowhittaker), were assessed with two PRN cutoff titers: a PRN titer of 8, the lowest detectable antibody level by the PRN test under the test conditions, and a titer of 120, which has been shown to be the minimum protective antibody titer. At a PRN cutoff titer of 8, the sensitivity was 88.2, 91.1, 74.6, and 69.8% for Behring, Diamedix, Vidas, and Biowhittaker EIA tests, respectively, with negative predictive values ranging from 22.7 to 45.5%. The specificity was 93.8% for Diamedix and 100% for the rest. At a PRN cutoff titer of 120, the sensitivity and specificity, respectively, were 100 and 90.7% (Behring), 98.2 and 58.8% (Diamedix), 90.6 and 94.5% (Vidas), and 85.7 and 96.4% (Biowhittaker). At this PRN cutoff titer, the negative predictive values of all EIA tests improved considerably, ranging from 70.7 to 100%. The EIA results showed an excellent association with PRN results when the PRN titers of the test samples were either < 8 or > 1,052. Discrepancies occurred especially when testing samples having PRN titers in the range of 8 to 120, indicating lack of sensitivity of the EIA tests in detecting measles virus antibody at low levels. Maternally derived measles virus antibody at this level has been shown to interfere with measles vaccine response in children and hence has implications from the standpoint of measles immunization.(ABSTRACT TRUNCATED AT 250 WORDS)