PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “False Negative Reactions”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
PubMed1974

Specificity and sensitivity of the streptozyme test for the detection of streptococcal antibodies.

A comparison between the results of the streptozyme hemagglutination test and serological titers for anti-streptolysin O (ASO), anti-hyaluronidase (AH), anti-deoxyribonuclease B (ADN-B), and anti-nicotinamide adenine dinucleotidase (ANAD) was made in two groups of human sera. In one group, serological titers for all the four antibodies were lower than the threshold of sensitization reported by the producing firm. In the second group, the titer of at least one of the four antibodies was equal to or higher than the threshold. False-positive and false-negative reactions occur with those sera when one or more antibody titer is at or near the threshold of the test as described by the manufacturer. The test was positive for all sera where either the ASO was greater than 166 or the ANAD was greater than 270, and for 98% of the sera with ADN-B greater than 360. It is, therefore, concluded that the streptozyme test can be used as an adjunct to the clinical diagnosis of streptococcal infections and their nonsuppurative sequelae. It is less useful to assess the levels of antibodies in sera from general population surveys. For such sera, the relative specificity and sensitivity of the test might yield misleading results. Until more experience is gained with the test, caution should be used in its application to infant and older adult age groups, where significant streptococcal antibody titers are frequently near the threshold of the test.

Antibodies, Bacterial↗
PubMed1982

Acetylthiocholinesterase staining activity of rectal mucosa. Its use in the diagnosis of Hirschsprung's disease.

Increased acetylthiocholinesterase (AchE) reactivity in the rectal lamina propria and lamina muscularis mucosae was used to diagnose Hirschsprung's disease. We processed 131 specimens with the AchE reaction; 43 were suction biopsy specimens and the rest were full-thickness specimens. Of the 68 specimens in which neurocytes were present, none demonstrated a diffuse increase in the number of nerve fibers. However, 15 showed focal increases in the numbers of fibers that were not large enough to be regarded as indicative of Hirschsprung's disease. All patients with a diffuse increase in nerve fibers, regardless of the type of biopsy, were shown to have Hirschsprung's disease. The AchE staining reaction did, however, produce a 29% rate of false-negative reactions (16 of 56 specimens) in patients with Hirschsprung's disease. These data demonstrate that an abnormal pattern of AchE reaction is diagnostic of aganglionic megacolon, whereas a normal pattern does not exclude the disease.

Acetylcholinesterase↗
PubMed1975

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↗
PubMed1976

[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↗
PubMed1989

Clinical evaluation of a direct fluorescent monoclonal antibody test for detection of Pseudomonas aeruginosa in blood cultures.

A direct fluorescent monoclonal antibody test (DFA; Genetic Systems Corp., Seattle, Wash.) was evaluated for the detection of Pseudomonas aeruginosa in 178 blood culture broths obtained from 128 patients. The DFA identified 44 (98%) of 45 blood cultures positive for P. aeruginosa and was negative in 131 (98%) of 133 blood cultures which grew gram-negative rods other than P. aeruginosa. Upon further investigation, saline suspensions of the organism from the false-negative blood culture were strongly (4+) DFA positive. The false-positive reactions were not due to cross-reactivity, as shown by lack of DFA staining of the non-P. aeruginosa isolates following subculture to agar media. The specificity of the reagent was further demonstrated by directly staining culture isolates including 10 serotypes of P. aeruginosa (all positive) and 57 selected gram-negative bacilli including eight species of Pseudomonas that were not P. aeruginosa (all negative). DFA staining of blood culture broths was easy to perform and read with minimal background fluorescence. The DFA method can be performed in 50 min and appears promising as a rapid method for the identification of P. aeruginosa bacteremia.

Antibodies, Monoclonal↗
PubMed1997

[Contact eczema induced by propylene glycol. Concentration and vehicle adapted for for patch tests].

INTRODUCTION: Contact dermatitis to propylene glycol, a widely used compound, is often difficult to evidence with skin tests. CASE REPORTS: We observed three cases of contact eczema to a dermal cream (Zovirax) used for labial herpes simplex. Patch-tests were positive in all three cases when the entire product was used but negative for each of the constituent components. The initial diagnosis could be an allergic reaction to the composition between the components as has been described elsewhere. Skin tests were completed with patch-tests using propylene glycol at concentrations over 5 p. 100 or with a vehicle other than vaseline (commercial tests use 5 p. 100 propylene glycol in vaseline). The results of these tests provided evidence allowing the diagnosis of contact dermatitis to the dermal cream due to allergic reaction to propylene glycol. DISCUSSION: Our three cases illustrate the frequency of false negative reactions to propylene glycol on commercial patch-tests. In agreement with data in the literature, these tests show that propylene glycol must be used at concentrations up to 10 to 20 p. 100 to identify allergic reactions with patch-tests.

Acyclovir↗
PubMedDate not supplied

Polyclonal enzyme immunoassay method for detection of motile and non-motile Salmonella in foods: comparative study.

A new enzyme immunoassay (EIA) method for detection of motile and non-motile Salmonella was examined in a comparative study. This method uses a proprietary formulation of polyclonal antibodies to Salmonella and is controlled to maintain specificity. Sensitivity is enhanced with an additional antibody reaction designed to minimize false-negative reactions attributable to steric interference that can occur during conjugate binding in immunoassay procedures. Twenty food types representative of a wide variety of food products were analyzed by both the EIA method and the AOAC/Bacteriological Analytical Manual (BAM) method, 967.26. Of the 1000 samples analyzed, there was a 95.6% agreement rate between the EIA method and the AOAC/BAM method. False-negative rates for the 2 methods were comparable for all foods and all Salmonella levels except ground poultry, where the EIA method detected significantly more confirmed positive samples than did the AOAC/BAM method. Twenty-seven samples were positive by EIA but negative by the culture method, and 17 samples were negative by EIA but positive by the culture method. There were no false-positive isolates detected in the comparative study.

Animals↗
PubMed1996

[Value of nucleic acid amplification methods Amplicor (Roche) and Amplified MTD (Gen-Probe) for the rapid diagnosis of tuberculosis].

The nucleic acid amplification methods: Amplicor (Roche diagnostic) and AMTD Amplified Mycobacterium tuberculosis Test Direct-(Gen-Probe) were tested in 278 specimens from 231 patients suspect to be affected by mycobacterial infection. When results of both methods: Amplicor and AMTD were compared with culture results (specimens grow M tuberculosis) and clinical characteristics, the sensitivity and specificity were 91.4% and 97.9% respectively for pulmonary specimens and 61.1% and 98.6% respectively for extrapulmonary specimens. Detection of amplification inhibitors reduce false-negative reactions and control of specimen with microscopic negative and amplification positive, reduce the false-positive reactions. Amplicor and AMTD kits can be used in clinical laboratories. Both assays have the potential to reduce the time of tuberculosis diagnosis to one day.

Bacteriological Techniques↗
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↗
PubMed1978

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↗
PubMed2004

Poor correlation between stated and found concentrations of diphenylmethane-4,4'-diisocyanate (4,4'-MDI) in petrolatum patch-test preparations.

Diphenylmethane diisocyanate (MDI) is widely used in its polymeric form in the manufacturing of polyurethane products. Previous reports on MDI-related contact allergy have shown a pattern, where patients seem to react to their own MDI-based work material but not to commercial patch-test preparations, which contain 4,4'-MDI. Therefore, we performed chemical analyses of 14 commercial test preparations of 4,4'-MDI obtained from 8 European and 4 American dermatology departments as well as 2 preparations from 2 major European suppliers of patch-test allergens. A new method for monitoring 4,4'-MDI in petrolatum preparations was developed and the determination of 4,4'-MDI as the MDI-dibutylamine derivative using liquid chromatography-mass spectrometry was performed. None of the preparations obtained from the dermatology departments contained more than 12% of the concentration stated on the label. In most cases, 4,4'-MDI content was only a few percentages or less of the concentration stated. 7 of the 14 preparations were analysed before the expiry date. Yet, only 1 of them, a preparation directly obtained from the supplier, came close to the concentration stated on the label. Thus, using these preparations, patients will be tested with a lower concentration than intended, leading to possible false-negative reactions.

Allergens↗
PubMedDate not supplied

Serological diagnosis of erythema migrans disease and related disorders.

An indirect immunofluorescence technique for the determination of antibodies against ixodid tick spirochetes is described. Differences in the reactivity between Ixodes ricinus spirochete and Ixodes dammini spirochete antigens were not observed. Cross-reacting antibodies against Treponema pallidum and Treponema phagedenis can be eliminated by quantitative absorption with T. phagedenis. Cross-reactions with leptospira were not observed by immunofluorescence. In the IgM test, false negative reactions caused by high-titered specific IgG antibodies or false positive reactions caused by rheumatoid factor occur. This can be avoided by testing the IgM fraction (19S-IgM-test) or using sera previously treated with anti-IgG serum. Significantly elevated antibody titers against ixodid tick spirochetes were observed in 45% of 44 cases with erythema migrans disease, in 72% of 29 cases of lymphocytic meningoradiculitis, in all of nine patients with acrodermatitis chronica atrophicans and in all of four investigated patients with lymphocytoma (lymphadenosis benigna cutis).

Acrodermatitis↗
PubMed1969

Time, cost, and efficacy study of identifying group A streptococci with commercially available reagents.

During the 12-month period primary throat, wound, and skin cultures, tentatively identified as B streptococci, were submitted by 10 different clinical laboratories for evaluation. A total of 692 beta-hemolytic streptococci were isolated from cultures submitted and examined in parallel by the fluorescent-antibody, precipitin, and bacitracin techniques. An evaluation of the specificity and sensitivity in conjunction with basic and personnel costs was determined for each method. The standard Lancefield precipitin method was established as the standard by which the bacitracin and flourescent antibody techniques were compared. With some variation depending on the commerical source of the disc, approximately 7% of the strains examined produced false reactions with the bacitracin disc. False-negative reactions were rarely noted by the group A fluorescent antibody technique (0.5%), but an appreciable number of other Lancefield groups (B, C, and G) were nonreactive with homologous conjugates.

Bacitracin↗
PubMed2001

Improved flow cytometric detection of HLA alloantibodies using pronase: potential implications in renal transplantation.

BACKGROUND: Flow cytomeric crossmatch (FCXM) has grown in popularity and has become the "standard of practice" in many programs. Although FCXM is the most sensitive method for detecting alloantibody, the B cell FCXM has been problematic. Difficulties with the B cell FCXMs have been centered around high nonspecific fluorescence background owing to Fc-receptors present on the B cells and autoantibodies. To improve the specificity and sensitivity of the B cell FCXM, we utilized the proteolytic enzyme pronase to remove Fc receptors from lymphocytes before their use in FCXM. METHODS: Lymphocytes isolated from peripheral blood, spleen, or lymph nodes were treated with pronase and then used in a three-color FCXM. A total of 167 T- and B cell FCXMs using pronase-treated and untreated cells were performed. Testing used serial dilutions of HLA allosera (22 class I and 6 class II), with the titer of each antibody at one dilution past the titer at which the complement-mediated cytotoxicity anti-human globulin crossmatch became negative. RESULTS: After pronase treatment, the actual channel values of the negative control in both T cell and B cell FCXMs declined from 78+/-10 to 57+/-4 (P<0.05) and 107+/-11 to 49+/-3 (P<0.00001), respectively. Pronase treatment resulted in improved sensitivity of the T and B cell FCXM in detecting class I antibody by 20% and 80%, respectively. In no instance was a false-positive reaction observed. In this study, pronase treatment improved the specificity of B cell FCXM for detecting class II antibodies from 75% to 100% (P=0.03). In no instance was a false-negative reaction recorded. Lastly, on the basis of these observations we re-evaluated three primary transplant recipients who lost their allografts because of accelerated rejection. One of the patients was transplanted across negative T and B cell FCXM, whereas the other two patients were transplanted across a positive T cell, but negative B cell, FCXM. After pronase treatment, T and B cell FCXMs of each patient became strongly positive, and donor-specific anti-HLA class I antibody was identi. fied in each case. CONCLUSION: Utilization of pronase-treated lymphocytes improves both the sensitivity and specificity of the FCXM.

False Negative Reactions↗
PubMed1998

False negativity by an anti-HIV assay kit (IMx 8B32) and evaluation of its replacement (IMx 8C98).

False negativity in a commercial anti-HIV kit (IMx HIV-1/HIV-2 3rd Generation Plus (code 8B32) was investigated, and the kit that superseded it (IMx HIV-1/HIV-2 III Plus, code 8C98) was evaluated. In a comparison on 574 freshly collected anti-HIV-1-positive specimens, 97.2% were more reactive in 8C98 than in 8B32; 35.5% were more than twice as reactive and 8.5% were more than four times as reactive. In 8B32, the signal from 55 specimens selected because of weak reactivity was enhanced 1.5 to 8.8 times by preliminary heating at 56 degrees C for 30 min. The reactivity of the 55 heated sera was then similar to that of the same specimens tested without heat treatment in the 8C98 assay. Reactivity in 8B32 was also increased in 66 of 76 (at least twofold in 20) randomly chosen anti-HIV-positive serum specimens by the addition of EDTA (10 mM final concentration). One of these specimens was false negative (signal:cutoff (S:CO) ratio 0.76) in 8B32, though its reactivity was restored by addition of EDTA (S:CO ratio 9.54). These findings indicate that the inhibitory effect that originally led to false negative findings in 8B32 was probably due to complement activity, and that the same activity was present in the freshly collected specimens used here to evaluate the replacement IMx anti-HIV assay (8C98). The specimen panel employed to evaluate 8C98 included 1,892 anti-HIV-positive and 779 anti-HIV-negative specimens. There were no false negative reactions. The lowest S:CO ratio observed was 6.2 and only 17 (0.2%) anti-HIV-positive specimens gave ratios less than 10. Nine unreproducible false positive reactions arose, all possibly attributable to specimen carryover by the IMx instrument. The performance of 8C98 was also compared with that of 10 other current anti-HIV kits using 21 sets of seroconversion specimens (127 specimens in total), and five performance assessment panels (92 specimens in total) comprised mostly of single bleeds from recent seroconverters. IMx 8C98 was the second most sensitive assay. We found no evidence that the 8C98 kit was prone to the effect that had given rise to false negative results in its predecessor (8B32).

AIDS Serodiagnosis↗
PubMed1990

Improved radioassay of anti-acetylcholine receptor antibody: application for the detection of extremely low antibody titers in sera from patients with myasthenia gravis.

We examined sera from 113 patients with myasthenia gravis (MG). Most of the patients with ocular MG without thymoma and 15% of the patients with generalized MG had immunoprecipitation (IP) titers of anti-acetylcholine receptor (anti-AChR) antibodies within the normal range for healthy subjects. We developed a highly sensitive radioassay using Staphylococcus aureus cells, and re-examined the 86 serum samples that had negative titers by IP. Using the radioassay, we detected anti-AChR antibodies in 27 (31%) of these myasthenic sera, of which 19 were from ocular MG patients without thymoma. By combining the standard IP assay and our new radioassay, we increased to 50% the overall percent positivity of detecting nonblocking-type antibodies in ocular MG patients without thymoma. We detected no anti-AChR antibodies in nearly all patients with various immunological and neurological diseases other than MG, and in all the healthy controls. The data for these sera indicate that in some cases the standard IP assay gives false-negative reactions. Thus, use of the more sensitive radioassay is preferable for accuracy.

Acetylcholine↗