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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

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

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

Acetylcholinesterase histochemistry of rectal suction biopsies in the diagnosis of Hirschsprung's disease.

Rectal suction biopsy with acetylcholinesterase (AChE) histochemistry has gained increased acceptance as the means of definitely diagnosing Hirschsprung's disease (HD) as well as of excluding this diagnosis when evaluating children with low intestinal obstruction or chronic constipation since the report of Meier-Ruge et al. in 1972. But this AChE histochemical study has not been reported yet in Korea. During the 14-month period from April, 1991 through June, 1992, 37 children, aged 3 days to 17 years had rectal suction biopsies for the diagnosis or exclusion of HD. In this study, AChE histochemistry (N = 37) was compared with hematoxylin & eosin (H&E) staining of same suction biopsy specimens (N = 35) for diagnostic accuracy. The histochemical criterion used for the diagnosis of Hirschsprung's disease was that of Chow et al. (1977), i.e., the presence of many coarse discrete cholinergic fibers in the muscularis mucosae and in the immediately subjacent submucosa regardless of an infiltration of cholinergic fibers in the lamina propria. Of 13 biopsies from the patients with Hirschsprung's disease (N = 13), there were 12 positive reactions, and one false negative reaction in a neonate with total colonic aganglionosis. All biopsies from 24 unaffected children demonstrated negative reactions with no false positive reaction. In comparison, of the 35 specimens examined by H&E staining, ganglion cells were present in the submucosal Meissner's plexus only in 15 of these 24 unaffected children. In conclusion, a 97% diagnostic accuracy was achieved with AChE histochemistry compared with a 74% accuracy with H&E staining (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase

A new radioimmunoassay for demonstrating the antibody to hepatitis-B-surface-antigen(HBs-Ag).

A new radioimmunological system for demonstrating the antibody to hepatitis-B-surface-antigen (HBS-Ag) based on the immunoadsorption principle is described. The optimal conditions for the test are given. False-negative and false-positive results could be excluded by specificity tests on sera from 100 voluntary blood donors. The sensitivity of the system is comparable to that of other more expensive radioimmunological methods.

Antibodies

Calf ligated intestinal segment test to detect enterotoxigenic Escherichia coli.

The ligated intestinal segment test in the young calf was utilized to establish the enterotoxigenicity of approximately 600 Escherichia coli isolates obtained from fecal specimens intestinal contents of calves with diarrheal disease. One hundred and fifty isolates were routinely tested in a single calf. There was little problem with false-positive reactions. False-negative reactions normally occurred only if the isolate was tested in the posterior 3 m of the small intestine. The ligated small intestine of the calf was distended by E. coli isolates of bovine, porcine, and human origin. Use of the calf ligated intestinal segment test is recommended to determine the enterotoxigenicity of E. coli isolates of bovine origin.

Animals

[Antibody monstration in blastomyces infections].

The evidence of humoral antibodies against yeasts can be a valuable help in the diagnosis of such infections. It is however necessary to use several sensitive methods, which complete one another in the detection of the different immunoglobulins. In the interpretation of the results the titer dynamic is decisive, especially in those patients whose antibody answer is suppressed by their disease and/or their therapeutic treatment. In most of the yeast infections Candida albicans can be used as antigen for the detection of antibodies because there is a strong relationship between the antigens of most of the yeasts important in human infections. C. krusei, C. pseudotropicalis and C. guilliermondii do not display enough common antigens to make a diagnosis against these yeasts possible with C. albicans. In that case homologous antigens have to be used. Cross reactions with other microorganisms are less frequent than usually supposed. Therefore so called false positive Candida titers have to be examined very carefully by clinical signs and culture methods.

Antibodies, Fungal

Comparison of methods for rapid immunofluroescent staining of group A streptococci and Neisseria gonorrhoeae.

Immunofluorescent staining reactions for group A streptococci and Neisseria gonorrhoeae were equivalent to those of standard "slow" methods when slides were heated on a serological water bath at 50 C for periods one to four minutes. No false negative reactions occurred when this method was used. False negative reactions occasionally occurred when previously described rapid methods which employed a slide warmer were used.

Fluorescent Antibody Technique

A study of co-positivity of three multipuncture techniques with intradermal PPD tuberculin.

One hundred thirty-five patients with a reaction of 10 mm or more of induration to 5 TU of intradermal PPD were simultaneously tested with 3 multipuncture techniques to determine the copositivity of the multiple puncture methods with the Mantoux method. Of the 3 multipuncture preparations used (Tine Test, Aplitest, and Mono-Vacc), the Mono-Vacc had 2 (1.5 per cent) false-negative result after 48 hours with only one remaining negative result after 72 hours; whereas the Tine-Test had 21 (15.5 per cent), and the Aplitest had 13 (9.6 per cent) false-negative reactions after 48 hours. Vesicular eruptions were not a commonly noted reaction to the multipuncture preparations. Of the 3 multipuncture preparations commercially available, Mono-Vacc is the preferred reagent because of its significantly lower incidence of false-negative reactions.

Adolescent

Reliability of chemical tests for fecal occult blood in hospitalized patients.

In 39 hospitalized patients with suspected gastrointestinal bleeding and given intravenous 51Cr-labeled red cells, reactions of three chemical spot tests for fecal occult blood were compared with the "true" blood loss as determined by stool radioassay. Guaiac reagent and orthotolidine (Hematest) tablets were extremely sensitive, but yielded false-positive reaction rates of 72% and 76%, respectively on the 240 stool specimens compared. A modified guaiac test (Hemoccult) exhibited a false positive rate of 12%. Of the 27 patients entering the study due to positive guaiac or Hematest screening tests, 17 (63%) were not bleeding. Hemoccult, approximately 1/4 as sensitive as guaiac and Hematest, could miss lesions with low rates of bleeding unless multiple stools were tested. While barium had no effect, iron therapy or laxatives tended to lower both false-positive and false-negative reactions for all reagents. A positive Hemoccult test usually indicated significant gastrointestinal bleeding and would appear to be the test of choice provided at least 3 stools are tested to minimize false-negative results.

Barium Sulfate

The value of the skin test and complement fixation test in the diagnosis of chronic pulmonary histoplasmosis.

Histoplasmin skin test results in patients with chronic pulmonary histoplasmosis from Missouri and Texas were compared to results in a previous study of U.S. Navy recruits. When consideration was given to geographic areas from which persons from each group were admitted to the study, it was found that the recruits were as likely to have a positive skin test as were those with the disease. In a similar manner, the Texas histoplasmosis patients were compared to groups of patients from that state with chronic obstructive pulmonary disease and with pulmonary tuberculosis. Again, no significant differences were found. It was concluded that the histoplasmin skin test is not of value in the diagnosis of chronic pulmonary histoplasmosis. Histoplasmosis complement fixation test data from the chronic pulmonary histoplasmosis group were compared to data from the chronic obstructive pulmonary disease and pulmonary tuberculosis groups. The usefulness of the complement fixation test in chronic pulmonary histoplasmosis is limited, as with any test, by false-positive and false-negative reactions. A decision theory method was used to define the limits of usefulness.

Chronic Disease

Use of immunoperoxidase on brain tissue for the rapid diagnosis of herpes encephalitis.

An indirect immunoperoxidase method to detect herpes simplex viral antigen in brain cell suspensions from patients suspected to have herpes encephalitis is described. The method is rapid, reliable and specific, and successfully identified the herpes virus infected cells in four of five culture-proven cases. There was one false-negative reaction, but no false-positive. The immunoperoxidase technic offers a number of advantages over immunofluorescence for routine diagnosis.

Antigens, Viral

[Evaluation of the monocyte test for diagnosis of allergic asthma bronchiale (author's transl)].

We investigated, if in routine work the relative simple monocyte test can improve the diagnostic yield of allergic asthma bronchiale in comparison with the inhalative allergen test. In 600 patients differential counts in peripheral blood were performed before, 30, and 60 minutes after inhalation of the allergen and the increase of monocytes was evaluated. Monocyte test and inhalative allergen test proved to be concordant in 67%, this value was statistically significant, but control trials failed in 11%. Therefore, the monocyte test fails to be of diagnostic value in allergic asthma, it does not increase additionally the diagnostic yield as a routine method.

Allergens

Experiences with radioimmunoassay in the detection of HBsAg in the presence of anti-HBs.

Interference from anti-HBs present during hepatitis B antigenemia caused the appearance of several false negative reactions in a competition radioimmuno-precipitation procedure. The results indicate that such interference is considerably less in the solid-phase radioimmunoassay (Ausria II) and probably causes few false negative tests. The use of pepsin treatment as a means to destroy interfering antibodies is discussed.

Antibodies, Viral

The tuberculin tine and Mono-Vacc tests in the patient with active tuberculosis.

Eighty-four patients with culture-positive Mycobacterium tuberculosis infections of the lung were evaluated with the Mono-Vacc and tine tuberculin skin tests. A previous report indicated that false negative reactions with the tine may occur in up to 6 per cent of patients when it is used as a screening device for tuberculin sensitivity. However, as indicated by this study, it is unlikely that either screening tests would miss active tuberculous infection; no false negatives occurred in the 84 patients.

Adolescent