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At least 19 recordsLinked to original sources
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↗
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↗
PubMed1976

Rubella hemagglutination-inhibition test: false-positive reactions in sera contaminated with bacteria.

We have shown that bacterial contamination of sera can have a marked influence on the results of the rubella hemagglutination-inhibition (HI) test. In addition to increasing the levels of nonspecific agglutinins, a number of common bacterial species tested had a significant effect on the HI titers. When sera free from rubella-specific antibodies were contaminated with Bacillus subtilis or Pseudomonas fluorescens, HI titers ranged from 16 to 128 (expressed as the reciprocal of the highest serum dilution completely inhibiting hemagglutination) after treatment with heparin/MnCl2. Our observations demonstrate, therefore, that bacterial contamination can be one of the causes of false-positive reactions in this test.

Bacillus subtilis↗
PubMed1979

False-positive reactions in the rapid plasma reagin-card, fluorescent treponemal antibody-absorbed, and hemagglutination treponemal syphilis serology tests.

Sera from 628 nonsyphilitic individuals were tested with the Rapid Plasma Reagin-Card, Fluorescent Treponemal Antibody-Absorbed, and Hemagglutination Treponemal Test for Syphilis tests to ascertain the comparative specificity of these tests. Many sera were also tested with the quantitative Venereal Disease Research Laboratory test. Sera included in the study were from both normal individuals and patients with a variety of illnesses and conditions. The Hemagglutination Treponemal Test for Syphilis gave the lowest overall percentage of false-positive reactions (1.6%), followed by the Fluorescent Treponemal Antibody-Absorbed test (3.3%) and the Rapid Plasma Reagin-Card test (10.8%).

Adult↗
PubMed1979

The occurrence and treatment of false positive reactions in enzyme-linked immunosorbent assays (ELISA) for the presence of fungal antigens in clinical samples.

Non-specific positive reactions have been revealed in enzyme-linked immunosorbent assays (ELISA) of sera for the presence of fungal antigen. These false positives were recognized by their occurrence in tests for both Candida albicans and Aspergillus fumigatus antigens and by their response to dithiothreitol, combined with their reaction with non-immune rabbit globulin. A scheme is proposed which differentiates between true and false positive reactions. Use of fractionated anti-fungal globulin in conjugates reduced the incidence of false positive results in sera from hospitalized patients and eliminated them from sera of healthy subjects. The test scheme was applied to two panels of sera containing samples from patients with (a) invasive candidosis and (b) invasive aspergillosis. The relevance of ELISA tests for the detection of fungal antigen in human serum is discussed.

Animals↗
PubMed1976

Studies on the origin of false positive reactions to the complement-fixation test for contagious bovine pleuropneumonia.

Serums of cattle free from contagious bovine pleuropneumonia (CBPP) were tested in complement fixation (CF) tests using 3 antigens; these were the standard antigen (SA) used to test to CBPP in Australia, an ethanol extract antigen (EA) also prepared from Mycoplasma mycoides subsp. mycoides (M. mycoides) and an antigen prepared from a Group 7 bovine mycoplasma isolated from arthritis (AA). The serums included 146 which fixed complement with SA. Eighty percent of these false-positive serums reacted with AA but not with EA; the other 20% were positive at low titre with EA but gave no reaction with AA. Attempts were made to produce false-positive serums experimentally by inoculating 3 Group 7 mycoplasmas and 2 Mycoplasma bovigenitalium strains into cattle. Serums from 3 of 9 cattle inoculated with strain L2917 (Group 7) reacted with SA but differed from the false-positive serums of field cattle by reacting with all 3 antigens. Tests with serums from cattle experimentally infected with CBPP gave similar titres with SA and EA, but the results with AA were mostly negative or less than 10% of the titres obtained with SA and EA. The results of CF tests on serums from the experimental cattle, after absorptions with suspensions of the mycoplasmas, showed that there was a one-way serological relationship between strain L2917 and M. mycoides and between this Group 7 strain and M. bovigenitalium. The CF tests with 3 antigens have assisted in demonstrating the false-positive nature of the reacting field serums encountered in the course of routine CF tests for CBPP in cattle in Australia.

Absorption↗
PubMedDate not supplied

False positive reaction for carboxyhemoglobin in blood from liver tissue.

On spectrophotometric determination of carboxyhemoglobin in blood collected from the liver of three bodies at three days post-mortem, false positive results were found (5--15 per cent saturation), since samples of heart blood collected a few hours after death did not contain carboxyhemoglobin.

Accidents, Aviation↗
PubMed1975

Gel precipitin tests for hepatitis-B surface antigen. False positive reactions due to the presence of staphylococcal antigen in contaminated plasma samples.

Plasma samples contaminated with coagulase-positive staphylococci were found to give a false positive precipitin line for hepatitis-B surface antigen in gel tests. The staphylococcal antibody was found to be present in both normal immunoglobulin and anti-hepatitis-B surface antigen immunoglobulin preparations and also in many normal plasma samples.

Antigens, Bacterial↗
PubMed1976

False-positive reactions of cerebrospinal fluid and diluted sera with the coccidioidal latex-agglutination test.

Most samples of cerebrospinal fluid from 49 patients with or without coccidioidomycosis yielded positive agglutination with the Hyland ("CM") latex-particle agglutination test. Furthermore, simple dilution of sera from patients with or without coccidioidomycosis yielded a strong agglutination reaction with the latex particle agglutination test reagent. These reactions were found with three lots of the latex-particle agglutination test reagent. One lot latex particles was found to give agglutination reactions merely by addition of saline solution or water, though a second lot did not. It is advisable, therefore, that the latex-particle agglutination test not be applied to cerebrospinal fluid, and that it be applied cautiously, particularly with diluted sera.

Coccidioidomycosis↗
PubMed1979

False positive reactions in the indirect fluorescent antibody test for Legionnaires' disease eliminated by use of formolised yolk-sac antigen.

The indirect fluorescent antibody (FA) technique for the diagnosis of Legionnaires' disease was used to investigate an outbreak of respiratory disease in a military population. The outbreak was later shown to be caused by an adenovirus. High titres were obtained using the ether-killed antigen supplied by the Center for Disease Control (CDC), Atlanta, but not with a formolised yolk-sac antigen prepared in out laboratory. The reactivity of these sera with the CDC antigen was removed by absorption with a partly identified gram-positive bacterium, whereas sera from persons with true Legionnaires' disease were unaffected by such treatment, suggesting that such reactivity is not specific for Legionnaires' disease. The lack of reactivity with negative control sera and strong reactivity from a small group of patients in whom seroconversion was demonstrated has led us to conclude that formolised yolk-sac antigen is a reliable antigen for the diagnosis of Legionnaires' disease by the FA method. Measurement of the sensitivity and specificity of the formolised yolk-sac antigen is still in progress.

Adenovirus Infections, Human↗
PubMedDate not supplied

False positive and false negative reactions in HLA B-27 antigen testing.

The recent commercial availability of HLA B-27 antiserum now enables laboratories without prior experience in HLA typing to test for this antigen. False positive and false negative reactions frequently occur and require judicious interpretation. In our laboratory, 30 of 100 specimens were positive for B-27 and 70 were negative. Of the 30 positive, 10 (33%) failed to react against every antiserum tested. Twenty-nine of the 70 negative specimens (41%) reacted falsely with one or more B-27 antisera. A significant cause of false positive reactions was cross-reaction of the B-7 antigen with B-27 antisera (13 of 15 B-7 positive, B-27 negative specimens). For valid B-27 testing, use of more than one B-27 antiserum is included.

False Negative Reactions↗
PubMed1979

Evaluation of three serological tests for the diagnosis of hydatid disease.

A number of techniques is used for the serological diagnosis of hydatid disease; however previous investigations suggest variable degrees or reliability for each test. This study reports an evaluation of the sensitivity and specificity of three commonly used serological tests for hydatid disease; complement fixation (CF), haemagglutination (HA) and the fluorescent antibody (FA) techniques. The results of these serological tests are compared in a series of specimens from 116 hospital patients, 21 of whom were confirmed surgically as having hydatid disease. A similar high degree of sensitivity was found for each of the three serological tests examined. The CF and HA tests gave negative results in two patients with confirmed hydatid disease, and the result of the FA test was negative in only one patient. The HA test was the most specific with no false positive reactions, but only two false positive reactions occurred with the FA test. The CF test was the least specific as the reaction was positive in nine patients without hydatid disease. When the results of both FA and HA tests were considered together, all 21 cases of hydatid disease were detected and false positive reactions occurred in only two patients.

Complement Fixation Tests↗
PubMed1978

The diagnostic efficiency of some serological tests for bovine brucellosis.

Results obtained from 1887 sera using three serological tests for bovine brucellosis were compared with a serological classification of sera described as the 'probable infection status'. Sera showing apparent false positive and apparent false negative reactions were identified, and were subjected to supplementary testing as appropriate. The serum agglutination test (SAT) gave 35% apparent false negative reactions and 5% apparent false positives. The complement fixation test (CFT) gave 12% apparent false negative reactions using warm fixation (CFTW) and at least 5% using cold fixation (CFTC). The routine diagnostic system used in Victoria, in which the CFTW is supplemented by the CFTC and the SAT, gave 9% apparent false negative reactions and 2% apparent false positive reactions. The radioimmunoassay gave 1% or 6% apparent false negative reactions, depending on the minimum diagnostic value used. Atypical reactions in the CFT sometimes caused difficulties in diagnosis.

Agglutination Tests↗
PubMed1977

Rapid detection of antibodies to cytomegalovirus by counterimmunoelectrophoresis.

A new method for the detection of precipitating antibody to cytomegalovirus by counterimmunoelectrophoresis (CIEP) is described. Fourteen of 15 adult sera (95%) with IgM-specific antibodies (as detected by immunofluorescence) and complement-fixing antibodies to cytomegalovirus in high titers gave positive reactions by this method. Control sera from 156 patients and 40 normal subjects were negative by CIEP. One of 32 individuals acutely infected with other members of the herpesvirus group gave a positive reaction (3%). False-positive reactions were restricted to a group of sera containing rheumatoid factor (10 of 31), but this activity could be eliminated by preliminary absorption of the sera with aggregated gamma-globulin. The present findings demonstrate that CIEP is useful for the detection of precipitating antibodies to cytomegalovirus in sera from acutely infected patients and promises to be a rapid, inexpensive screening procedure of diagnostic value.

Adult↗
PubMed1977

The use of preserved milk samples in the Brucella milk ring test.

Brucella milk ring tests (BMRT's) were performed on fresh herd milk samples and pooled samples, preserved at a processing factory with potassium dichromate. Preserved milk from samples pooled over a 10-day period, gave results that were similar to an average result for individual fresh daily samples over the same period. When fresh samples gave variable results and the pooled preserved sample gave a negative result, it was considered that the latter result was more reliable, possibly due to factors causing false positive reactions being diluted. Blood testing of herds for circulating antibody indicated that the use of either fresh or preserved milk samples could occasionally produce false negative or false positive results.

Agglutination Tests↗
PubMedDate not supplied

Comparison of three techniques for the detection of antibodies to double-stranded DNA: immunofluorescence on Trypanosoma gambiense, immunofluorescence on Crithidia luciliae and radioimmunoassay using the Farr technique.

Three techniques for the detection of antibodies against double-stranded DNA were compared: two immunofluorescent (IF) techniques using either Trypanosoma gambiense or Crithidia luciliae as antigen and a radioimmunoassay (RIA) based on the Farr technique. The IF on T. gambiense or C. luciliae gives very similar results but the reaction on C. luciliae is easier to read and to interpret. The use of C. luciliae permits the swift elimination of the two main causes of errors: antibodies against the nucleus of Trypanosomidae and antibodies reacting with the base of the flagella. The RIA appears as a very sensitive test since six sera gave a positive reaction with the RIA and a negative reaction with the IF on C. luciliae. However, the RIA gives in nine cases false positive reactions and in four cases false negative results. Those last four sera contained specific antibodies with low avidity for double-stranded DNA.

Animals↗