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Results for “False Negative Reactions”

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At least 19 recordsLinked to original sources
PubMed1993

Frequency of false-negative reactions to the fragrance mix.

To estimate the frequency of false-negative reactions to the fragrance mix, the 8 constituents of the mix in concentrations of 5% (2% for cinnamic aldehyde) were added to the European standard series for routine testing. Patients with positive reactions to individual ingredients in the absence of a reaction to the mix were retested with serial dilutions. In a 4-month period, 677 patients were tested. 61 (9%) reacted to the mix and to 1 or more of the ingredients. 4 patients (0.6% of all patients tested and 6.2% of the patients allergic to fragrances) had false-negative reactions to the mix. They were allergic to cinnamic alcohol, geraniol, isoeugenol and oak moss (1 reaction each), in the absence of a reaction to the fragrance mix. It is concluded that the currently used concentration of the mix (8 x 1%) not infrequently results in false-negative reactions, and that further research should be done to overcome this problem.

Dermatitis, Allergic Contact↗
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↗
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↗
PubMed1985

[False negative reactions in the serodiagnosis of cystic echinococcosis in humans].

Clinically supposed cases of echinococcosis can be strongly confirmed by application of serodiagnostic techniques. In certain cases false-negative reactions have to be taken into account. This has been observed in 4 out of 51 parasitologically confirmed cases. One patient had a hyalin cyst, a case in which supposingly no antigen diffused into the host's system. In two cases the cysts were calcified, in one patient only no explanation could be given.

Adult↗
PubMed2004

[False positive and false negative reaction results based on an amplification of nucleic acids in infection diagnoses. Reasons and implications].

The paper discusses the most frequent causes of false positive and false negative results of reactions based on amplification of nucleic acids. All stages of the method are described beginning with sample collection up to the finishing of visualization of amplification product. The main aim objective of the publication is to draw doctors' attention to the necessity to interpret the result with criticism. We attempted also to demonstrate how to avoid false results.

Animals↗
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↗
PubMed1981

[False negative reactions of the bicycle ergometry test in ischemic heart disease and stenosing arteriosclerosis of the coronary arteries].

The authors analyse 52 results of false-negative bicycle ergometry tests in patients with ischemic heart disease and stenosing coronary atherosclerosis (according to the findings of coronarography). During bicycle ergometry all patients attained submaximum pulse rate (85% of the maximum) and had a high tolerance (808 kgm/min, on the average) to exercise. False-negative results were encountered most frequently in isolated lesion of one of the coronary arteries (usually the left anterior descending branch). The frequency of myocardial ischemia detection during bicycle ergometry did not depend on the presence or absence of collaterals.

Adult↗
PubMed1987

Detection characteristics of a commercially available sulfite detection test (SULFITEST): problems with decreased sensitivity and false negative reactions.

Recently, a product (SULFITEST; Center Laboratories) has become available for detecting the presence of sulfiting agents in foods. Testing with SULFITEST by the indirect method (ie, holding the test strip above the food product) or the direct method (ie, touching the test strip directly on the food) was associated with false negative results in five out of nine acidic sulfite-containing foods. Quantitative studies also confirmed that low pH conditions and/or the presence of ascorbic acid caused SULFITEST results by the direct method to significantly underestimate known concentrations of sulfites. Dependence on this sulfite detection strip may lead to unrecognized ingestion of sulfiting agents, especially in acidic and/or ascorbic acid-containing foods.

Ascorbic Acid↗