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At least 37 records · Page 2Linked to original sources
PubMed1992

False positive reaction of heat-inactivated sera in enzyme-linked immunosorbent assay for antibody to hepatitis C virus.

Specimens were heated at 56 degrees C or 62 degrees C to analyze the mechanisms of false positive reactions in the Ortho enzyme-linked immunosorbent assay (ELISA) for the detection of antibody to hepatitis C virus (HCV). The highest correlation was obtained between the difference in HCV antibody titer of 56 degrees C-heated and native sera and IgG concentration. Monoclonal IgG gammopathy sera developed marked increases in the titer by preheating. However, slight increases after preheating were observed in monoclonal IgA gammopathy sera. Similar increases in the titer by preheating were also demonstrated in immunoglobulin products containing IgG. Direct bindings of denatured IgG with C100-3 and 5-1-1 antigens were shown in recombinant immunoblot assay (RIBA). These results could show the participation of denatured IgG in the false positive reaction in Ortho-HCV-ELISA. Caution is necessary in evaluating the anti-HCV antibody titers of heat-inactivated sera.

Enzyme-Linked Immunosorbent Assay↗
PubMed1992

Removal of false-positive reactions from plasma in an enzyme immunoassay for bovine interferon-gamma.

A monoclonal antibody-based sandwich enzyme immunoassay (EIA) for bovine interferon-gamma (IFN-gamma) has been developed and can be used in conjunction with a whole blood culture system to diagnose tuberculosis in cattle. During its development, normal bovine plasma samples were tested to establish background levels of circulatory IFN-gamma. Of 191 samples tested, 81 (42.4%) were positive (OD > 0.1) when tested undiluted in intact monoclonal antibody (IgG1)-coated wells compared to only 8 (4.2%) in F(ab')2-coated wells, which suggested non-specific interference in the EIA rather than circulatory IFN-gamma. Reactivity of all remaining samples was removed by diluting plasmas 1/2 with 1% casein-PBS-0.05% Tween 20 supplemented with an optimum amount (5%) of normal mouse serum (NMS). Serum pools derived from BALB/c, DBA/2, C3H/HeJ, CBA/CaH and Swiss, but not C57BL/6J, mice were found to inhibit equally the reactions of five strong false-positive bovine plasma samples but had no effect on the titre of IFN-gamma in the sample. Sera from other species tested were less effective. This suggests that the interfering factors possess a high degree of specificity, since the immunoglobulin heavy chain of IgG1 produced by all these five strains of mice are allotypically identical and different to IgG1 produced by C57BL/6J mice. The use of F(ab')2 antibody fragments to coat plate wells and sample diluent containing 5% NMS has resulted in an EIA for bovine IFN-gamma that is virtually free from false-positive reactions, has a high degree of reproducibility and a sample detection limit equivalent to approximately 80 pg/ml recombinant bovine IFN-gamma.

Animals↗
PubMed2006

Pitfalls in drug allergy skin testing: false-positive reactions due to (hidden) additives.

Skin testing for drug hypersensitivity is a valuable diagnostic tool and a well established procedure for betalactams and corticosteroids. Although appropriate patch, prick or intracutaneous testing usually permits unequivocal interpretation, the possibility of false-positive reactions must be kept in mind. We report two patients, one with a suspected penicillin allergy and one with a suspected steroid allergy, in whom positive skin tests initially yielded a false diagnosis. In both cases, other findings were inconsistent with the positive skin tests. Therefore, further investigations were performed. After the test preparations had been analysed, the skin test was extended to include the additives, which then yielded the diagnosis of sensitization to the surfactant polysorbate 80 (PS 80, contained in the penicillin test solution) and the emulsion stabilizer carboxymethylcellulose (CMC, contained in the steroid preparation), respectively. It should be noted that positive reactions to test solution additives, as in the first case, may lead to a lifelong false diagnosis of (penicillin) allergy, whereas an undiagnosed allergy to additives in parenteral applications, as in the second case, might prove fatal.

Allergens↗
PubMed1966

False-positive reaction to VDRL test with prozone phenomena. Association with lymphosarcoma.

A patient with lymphosarcoma had a VDRL test reactive at 1:256. A prozone phenomenon was also present. The nontreponemal test result was shown to be a false-positive reaction by nonreactive Treponema pallidum immobilization and fluorescent treponemal antibody absorption tests. High-titer serologic tests for syphilis are uncommon, and prozone reactions are previously unrecorded in the false-positive reactor.

Diagnosis, Differential↗
PubMed1976

Albumin autoagglutinating phenomenon as a factor contributing to false positive reactions when typing with rapid slide-test reagents.

A case of albumin autoagglutination has illustrated the point that this phenomenon may be a further source of false positive reactions when typing with rapid slide-test reagents. As agglutination only occurred with the bovine albumin solution and slide-test reagents from a single manufacturer, it is evident that control tests must be performed not merely with a high protein solution duplicating the formulation of the slide-test reagent itself, but with one from the same commercial source as the reagent.

Drug Contamination↗
PubMed1989

Antibodies to bovine serum albumin in swine sera: implications for false-positive reactions in the serodiagnosis of African swine fever.

Antibodies to bovine serum albumin were detected in swine sera by use of an immunoblotting technique. Such sera had false-positive reactions, as determined by results of African swine fever virus serodiagnostic techniques when bovine serum albumin was a contaminant in the soluble cytoplasmic antigen obtained from infected cells cultured in the presence of bovine serum. The soluble cytoplasmic antigen obtained from cell cultures infected with African swine fever virus in the presence of porcine serum did not react with the false-positive sera and, therefore, was used for African swine fever virus serodiagnostic methods, with 0% false-positive results.

African Swine Fever↗
PubMed1992

Association of biologic false-positive reactions for syphilis with human immunodeficiency virus infection.

The prevalence of biologic false-positive (BFP) reactions for syphilis (reactive rapid plasma reagin [RPR] test, nonreactive fluorescent treponemal antibody absorption [FTA-ABS] test) among patients attending two sexually transmitted disease (STD) clinics was evaluated to assess relationships between BFP reactions and human immunodeficiency virus (HIV) infection. Among 4863 patients, 357 (7.3%) had serologic evidence of syphilis and 4.9% had HIV infection. Only 40 patients (0.8% of total patients, 11% of those with reactive RPR tests) had BFP serologic tests for syphilis. There were no demographic differences between true syphilis and BFP patients as to sex, age, or intravenous drug use. BFP patients tended to have lower RPR titers (less than or equal to 1:4) than did true syphilis patients. After excluding 317 patients with reactive FTA-ABS tests, BFP RPR tests were seen in 6 (4%) of 159 HIV-seropositive patients and 34 (0.8%) of 4387 HIV-seronegative patients (odds ratio, 5.0; 95% confidence interval, 1.9-12.7). Although more common among HIV-infected than HIV-uninfected patients, BFP reactions are relatively rare among STD clinic patients, and 89% of patients with reactive RPR or VDRL serologic tests for syphilis had current or prior syphilis infection. The RPR test remains useful for guiding decisions regarding therapy for syphilis.

Adult↗
PubMedDate not supplied

HLA antibodies as a cause of false-positive reactions in screening enzyme immunoassays for antibodies to human T-lymphotropic virus type III.

15,680 volunteer blood donors were screened by enzyme-linked immunosorbent assay (EIA) for antibodies to human T-lymphotropic virus Type III (HTLV-III). On at least two of three determinations, 0.37 percent were found to be reactive. When the first 38 of these samples were sent for repeat EIA and Western blot, the EIA was positive in 14. In only three of these 14 samples was the EIA result confirmed by Western blot. Eight of these eleven false-positive samples were from women who were found to have HLA antibodies. In seven of these women, the HLA antibodies were directed to Class II antigens expressed on the cell used to grow HTLV-III in the preparation of screening EIA kits. We conclude that HLA antibodies are an important cause of false-positive reactions in the screening test for HTLV-III antibody.

Adult↗
PubMed1965

TESTS FOR SYPHILIS. THE INCREASING INCIDENCE OF BIOLOGIC FALSE POSITIVE REACTIONS AS MEASURED BY TREPONEMA PALLIDUM IMMOBILIZATION.

Analysis of data obtained in 25,787 Treponema pallidum immobilization tests in a ten-year period showed an increase in the incidence of biologic false positive (BFP) reactions for syphilis, and a decrease in the incidence of reactive TPI tests. The percentage of BFP tests increased from 54.2 per cent in 1953 to 70.7 per cent in 1962. Reaction to a standard serologic test for syphilis (STS) indicates only that the patient may have syphilis. A subsequent non-reactive TPI test remains the best procedure for ruling out a diagnosis of syphilis. Thus the clinician should be made more aware of the fact that a biologic false positive reaction strongly implies the existence of another disease, the cause of which should be investigated.

Biological Products↗
PubMedDate not supplied

The problem of testing horse kidneys for the presence of antibiotics at meat inspection: how to avoid a false positive reaction.

When 33 horse kidneys were tested for the presence of inhibitory substances by the Bacillus subtilis BGA method at pH 8 and the Micrococcus luteus ATCC 9341 method, 24 were positive and 9 negative. The pH of the seeded M. luteus test medium changed from pH 6.6 before incubation to 8.7 after 24 hours incubation at 30 degrees C. When the same 33 kidneys were tested by the B. subtilis BGA method, medium pH 6, and 15 of them also by the M. luteus method using a medium buffered to pH 6, all were negative. The cadmium concentration of the 33 horse kidneys was found to be 70.17 +/- 81.28 mg/kg wet weight (m +/- s, range 10.40-355.67). The authors attributed the positive results to the presence of cadmium. The diffusion of cadmium from the horse kidney samples to the test media was found to differ at pH 6 and pH 8. It is recommended that the testing of horse kidney samples for the presence of antibiotics and chemoterapeutic substances be done at substrate pH 6 to avoid false positive reactions.

Animals↗