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PubMed1983

HLA typing of cultured amniotic fluid cells.

HLA typing was performed on 18 cultures of human amniotic fluid cells using cytotoxicity and absorption technics. Confirmation of antigen assignments was obtained in nine of ten instances, where HLA typing also was performed on cord blood. Three major problems were encountered in performing these studies: (1) complement cytotoxicity, (2) false-positive reactions, and (3) false-negative reactions. False-positive and false-negative reactions occurred more frequently with sera defining HLA-B locus specificities than with sera defining HLA-A locus specificities. Absorption studies were helpful in making antigen assignments when false reactions occurred. Preliminary studies suggest that the frequency of false-positive reactions can be decreased by absorbing HLA typing sera with antigen-negative amniotic fluid cultured cells, buffy coat, or platelets. Accurate antigen assignment is difficult when parental HLA types are unavailable.

Absorption↗
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↗
PubMed2002

[Systematic reviews in practice. X. Searching, selecting and the methodological assessment of diagnostic evaluation research].

Literature concerning the value of diagnostic tests is poorly indexed in electronic bibliographical databases. An extensive, sensitive and specific search strategy for evaluation of a diagnostic test in Medline is a combination of key words or text words concerning the diagnostic test with: 'sensitivity and specificity' (exploded), 'mass screening' (exploded), 'reference values', 'false positive reactions', 'false negative reactions', 'specificit$.tw', 'screening.tw', 'false positive$.tw', 'false negative$.tw', 'accuracy.tw', 'predictive value$.tw', 'reference value$.tw', 'roc$.tw' or 'likelihood ratio$.tw'. Inclusion and exclusion criteria select publications which meet certain minimum requirements, such as the presence of an accepted reference standard, a clear definition of 'diseased', and the presence of a suitable outcome measure. The methodological assessment list should contain a number of validity criteria as well as a number of criteria by which to measure the extent to which the study results can be generalised. Important assessment criteria that may affect the diagnostic value of the test are: study design, blinding, use of different reference standards, the absence of details about the diagnostic criteria for the diagnostic test and insufficient information about the study population.

Diagnostic Tests, Routine↗
PubMed1989

The sensitivity and specificity of the immediate-spin crossmatch.

The immediate-spin (IS) crossmatch is used to detect ABO incompatibility between donor red cells (RBCs) and the serum of the intended recipient. However, this test may be positive in the absence of ABO incompatibility (false positive) or it may be negative when ABO incompatibility exists (false negative). During a 25-month study, the rates of both false-positive and false-negative IS crossmatch results were evaluated, and the sensitivity and specificity of the IS crossmatch were determined. During the study period, 53,656 IS crossmatches were performed for patients without significant RBC antibodies. Fifty-five patients had positive IS crossmatches, and no false-negative reactions were found. In tests of 55 patients with positive IS crossmatches, 77 false-positive and 5 true-positive reactions were noted. The causes of the false-positive reactions were rouleaux (36 patients), cold-reactive antibodies (8 patients), a combination of rouleaux and cold-reactive antibodies (2 patients), fibrin clot (1 patient), and undetermined (3 patients). The sensitivity and specificity of the IS crossmatch were 100 and 99.86 percent, respectively. Laboratory personnel should be aware that the IS crossmatch may have false-positive or false-negative results, and they should develop written protocols to distinguish quickly between true-positive and false-positive reactions.

ABO Blood-Group System↗
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↗
PubMed1981

Comparative evaluation of the Iatron serological Candida check kit and the API 20C kit for identification of medically important Candida species.

A newly developed commercial serological test (Iatron Laboratories, Inc., Tokyo, Japan) for the rapid identification of medically important species of Candida was evaluated against the API 20C (Analytab Products, Plainview, N.Y.) and the standard Wickerham assimilation and fermentation procedures. Our results indicated that the Iatron and the API 20C methods are 95% accurate since both permitted identification of 78 of 82 Candida isolates, representing eight medically important species. None of the tests on nine Cryptococcus, six Trichosporon, three Geotrichum, three Saccharomyces, and one Rhodotorula species yielded false-positive reactions. False-positive serological tests occurred with a species of Pichia and Candida rugosa. The API 20C procedure correctly identified C. rugosa but not the Pichia sp. The Iatron method permitted reliable identification of the Candida species in 10 min to 5 h, whereas the API 20C procedure required 48 to 72 h. Neither method could properly identify sucrose-negative Candida tropicalis or Candida lusitaniae isolates. In addition, Candida albicans isolates could be serotyped by the Iatron method.

Agglutination Tests↗
PubMed1991

Solid phase capture method for the specific amplification of microbial nucleic acids--avoidance of false-positive and false-negative reactions.

DNA amplification assays such as the polymerase chain reaction are being developed for the amplification of small quantities of microbial nucleic acids. These assays offer the potential for a great deal of sensitivity. However, the high level of sensitivity increases the likelihood of cross-contamination of amplified products and the generation of false-positive reactions. In addition, substances in body fluids can inhibit the efficient performance of the amplification reactions. We have developed an assay format in which microbial nucleic acids are specifically bound to a solid phase surface. Contaminating DNA and enzyme inhibitors present in the sample are removed by washing prior to the performance of the amplification reaction. We could use this system to amplify and detect small amounts of HIV DNA diluted in whole blood. The assay system could distinguish target DNA from contaminating DNA fragments generated by prior amplification reactions.

Base Sequence↗
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↗
PubMed1976

Predictive value of cross-matching for transfusion of platelet concentrates to alloimmunized recipients.

Compatibility tests in which donor platelets were tested with recipient sera were performed retroactively after 64 transfusions of platelets from 59 unrelated donors to 10 alloimmunized patients. Techniques used were serotonin release, aggregometry, platelet factor 3 release, and lymphocytotoxicity, each of which has been advocated as a means of testing donor-recipient platelet compatibility. Although "false positive" reactions were few (positive crossmatch but satisfactory transfusion response), "false negative" reactions (negative crossmatch but poor transfusion response) were unacceptably high (43% by lymphocytotoxicity, 60% by serotonin release, 76% by platelet factor 3 release, and 83% by aggregometry). We conclude that current methods of detecting isosensitization to platelet alloantigens are less satisfactory than HLA phenotyping in selecting unrelated platelet donors for an alloimmunized patient population.

Blood Platelets↗
PubMed1988

False positive and false negative reactions encountered in the use of sulfite test strips for the detection of sulfite-treated foods.

The reliability of a qualitative test for sulfites in foods (Sulfitest sulfite test strips) was evaluated by comparison of the results obtained from the analysis of 90 food and beverage samples to results obtained by the quantitative, modified Monier-Williams method (the preferred procedure for sulfite analysis in foods of the Food and Drug Administration). The results obtained with the sulfite test strips compared favorably to the results of the Monier-Williams procedure when the sulfite test strips were used on sulfite-treated lettuce and raw or cooked potatoes. However, the strips yielded many false negative and false positive results with other types of foods. False positive results (strips indicated a substantial amount of sulfite when sulfite was not detectable by the Monier-Williams method) were obtained with fin fish, red meats, and poultry. False negative results (strips indicated the absence of sulfites when sulfite was detected at levels greater than 10 ppm total sulfur dioxide by the Monier-Williams method) were obtained with dried fruits and wines under certain conditions of testing. The false negative responses with the test strips may result in the hazardous consumption of foods with high levels of sulfites, such as dried fruit or wine, by a sulfite-sensitive individual. The false positive responses would not be hazardous but could lead sensitive individuals to avoid foods that could be safely consumed. Although the strips may be useful for the detection of sulfites in certain foods, such as lettuce and potatoes, their use by sulfite-sensitive individuals cannot be recommended because of the confusion and potential hazards posed by the false negative and false positive responses.

False Negative Reactions↗
PubMed1985

Biological false positives to serological tests for syphilis in herpes genitalis.

A survey was made of 17 patients (4 females and 13 males) with herpes genitalis who, during period 1971-84, developed biological false positive serological tests for syphilis. Of 121 patients with herpes genitalis diagnosed by herpes culture in 1982-84, 4.1% developed biologically false positive reaction. Duration of symptoms before biologically false positive reaction was 12 days. Duration of false positive reaction was on average 32 days. Eight had borderline reactions, 7 uneven positive titers and 2 serological patterns simulating secondary syphilis.

Adolescent↗
PubMed1994

Serological tests for Lyme disease in patients with tropical spastic paraparesis and healthy Jamaicans.

The significance of reactive serological tests for Lyme disease in patients with tropical spastic paraparesis (TSP) was assessed by examining serum samples from 128 of these patients and 200 healthy Jamaicans by Lyme indirect immunofluorescent antibody (IFA), enzyme immuno-assay (EIA) and Western blot analyses. Sera were also examined in serological tests for syphilis (STS), an unabsorbed fluorescent treponemal antibody test and leptospira microagglutination test. The prevalence of positive Lyme IFA and EIA results did not differ significantly between sera from TSP patients (12.5%) and healthy controls (10.0%). Western blot analyses showed that the positive Lyme IFA and EIA results observed in this study were due to false positive reactions. Seventy-five per cent of Lyme IFA/EIS positive sera from TSP patients had treponemal antibodies. Eighty per cent of those from healthy controls were negative in standard STS but 85% were positive when tested in an unabsorbed fluorescent treponemal antibody (FTA). These data indicate that reactive serological tests for Lyme disease in Jamaican TSP patients and healthy Jamaicans are false positive reactions due to cross-reactivity with other spirochaetes, notably Treponema pallidum and non pathogenic treponemes.

Adolescent↗
PubMed1970

Synergistic false-positive coliform reaction on M-Endo MF medium.

The reported occurrence of synergistic false-positive coliform reactions on M-Endo MF medium was investigated. The objectives of the study were (i) to isolate populations of bacteria which produced such false-positive reactions, (ii) to determine whether false-positive sheen reactions are a result of synergistic interaction, and (iii) to determine the metabolic intermediates involved in false-positive sheen production. Samples of river water were subjected to coliform analysis by the membrane filter technique with M-Endo MF medium. Suspect sheen-forming colonies were analyzed to determine purity and identity of cultures. Mixed cultures were separated, and individual isolates were examined for sheen production. The isolates not producing a sheen were recombined and tested further for sheen production. Those mixtures reproducing the sheen were characterized biochemically and tested to determine the metabolic intermediates involved. Chromatographic analysis of the metabolites showed that individual isolates produced an assortment of neutral organic compounds including 2-butanone, 2,3-butanedione, formaldehyde, and butyraldehyde, whereas acetaldehyde or propionaldehyde was produced only by the mixed cultures. Tests showed that both propionaldehyde and acetaldehyde could react to produce a sheen on M-Endo medium. The conclusion was reached that synergistic false-positive coliform reactions do indeed occur on M-Endo MF medium.

Aldehydes↗
PubMed1983

Hybridoma antibody-based competitive ELISA in Schistosoma japonicum infection.

A competitive enzyme-linked immunosorbent assay (ELISA) has been developed and compared with the circumoval precipitin test (COPT) for diagnosis of schistosomiasis japonica using Philippine sera. The assay is based on the inhibition, by sera, of the binding of a penicillinase-conjugated hybridoma-derived antibody, I. 134, to a crude Schistosoma japonicum adult worm extract. A change in pH subsequent to addition of the substrate is used as the indicator system. Development of the color change in this assay is relatively slow, a fact which presumably facilitates detection of inhibition by serum. Relative to the COPT, no false positive reactions were obtained and the false negative rate was less than 10%. A wide range of inhibitory titers was obtained using sera in the competitive ELISA similar to that found in a competitive radioimmunoassay using 125I-labeled I. 134. The competitive ELISA will be of more general application for diagnosis of schistosomiasis japonica than the competitive RIA using hybridoma antibodies, and will provide more precise quantitative information than is obtainable in the COPT.

Antibodies↗
PubMed1988

An assessment of urease-based enzyme-linked immunosorbent assay.

The use of urease in enzyme-linked immunosorbent assays (ELISAs) offers the advantages of convenience and safety. However, urease-based ELISA, performed in standard microtitre format, could result in false positive reactions upon prolonged incubation. False positive reactions appeared when wells containing substrate solution absorbed ammonia liberated from a reactive well nearby. Thus, the intensity of the false reaction was proportional to that of the urease reaction. The transfer of ammonia was demonstrated by pyrolysis-mass spectrometry. When urease conjugates were compared with peroxidase conjugates in the detection of IgG and IgM, there was no evidence that one enzyme was superior to the other in terms of increasing the sensitivity or the speed of ELISA.

Ammonia↗
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↗
PubMed1996

Infection of cattle with Yersinia enterocolitica O:9 a cause of the false positive serological reactions in bovine brucellosis diagnostic tests.

During the last four years, an increasing number of cattle herds were classified positive by brucellosis screening tests in areas of Belgium and France free of the disease. No clinical symptom of brucellosis was reported in these animals and no Brucella abortus strains were isolated. After two years, no brucellosis outbreak was registered in all of the herds concerned. On this basis, all the serological reactions observed were classified as false positive. An ELISA using Yersinia Outer membrane Proteins (YOPs) as antigens was developed in order to discriminate between a Yersinia enterocolitica O:9 infection and a Brucella abortus infection. Antibodies against YOPs were detected in sera from Y. enterocolitica O:9 experimentally infected cattle (n = 4) but not in sera from B. abortus experimentally infected cattle (n = 4). In a field study, 66.7% of the 174 serum samples from cattle presenting false positive serological reactions showed anti-YOPs antibodies whereas only 10% of 454 sera, classified negative by the brucellosis screening tests, showed anti-YOPs antibodies. Our results suggest that infections with Y. enterocolitica O:9 may cause false positive reactions in brucellosis testing.

Animals↗