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Results for “False Negative Reactions”

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PubMed2006

Should macular erythema reactions be counted as positive allergic patch-test reactions?

BACKGROUND: Positive allergic patch-test results are generally described as erythematous papules, vesicles, or a spreading reaction with crust and ulceration. This description excludes milder reactions, including macular erythema. OBJECTIVE: Our aim was to investigate the prevalence and relevance of reactions graded as macular erythema at Mayo Clinic. METHODS: Between January 2001 and June 2004, patients suspected of having allergic contact dermatitis were patch-tested with our institution's standard patch test, a screening series of 68 to 72 allergens. In total, 2,823 patients were patch-tested with 193,530 allergen applications. Reactions were interpreted with the North American Contact Dermatitis Group scale, including and excluding reactions graded as macular erythema. Irritant reactions were excluded from calculations. For this study, scores for current, questionable, and past relevance were combined. RESULTS: On day 5, with the exclusion of reactions graded as irritant, 7,274 allergen applications were associated with reactions, including 3,082 (42.4%) that were graded as macular erythema. Of the macular erythema reactions, 2,430 (78.8%) were graded as relevant. The rate of reaction in our patients was 2.2% if macular erythema was excluded, 3.8% if all macular erythema reactions were included, and 3.4% if only those macular reactions deemed relevant were included. CONCLUSION: Patch-test reactions rated as macular erythema are common and may be of clinical relevance. For the purposes of patient education, they should not be disregarded. Consideration should be given to including these reactions when reporting patchtest results.

Allergens↗
PubMed1976

Further observations on tuberculin reactions in active tuberculosis.

One hundred patients with active tuberculosis were tested for tuberculin reactivity within 24 hours of their admission to the hospital. Commercial intermediate tuberculin, Tween stabilized intermediate tuberculin and the Tine test as well as a mumps antigen were applied simultaneously. False negative reactions were obtained in 28 per cent with Tine testing and in 21 per cent with Tween stabilized as well as plain tuberculin. These nonreactors were clinically identifiable as seriously ill with manifestations primarily attributable to protein depletion as a result of their illness. This is not specifically related to the effects of tuberculosis itself, but can be demonstrated in patients suffering the same sequelae of other debilitating illness. After two weeks of protein supplementation via a high calorie, high protein, hospital diet, skin reactivity was restored in the vast majority of these nonreactors. It is concluded that the lack of tuberculin reactivity on hospital admission probably results from impaired lymphocyte function in patients suffering serious protein depletion as a result of their illness; it is not attributable to deficiencies in the tuberculin test itself.

Adult↗
PubMed1994

Rapid direct diagnosis of deletions carriers of Duchenne and Becker muscular dystrophies.

13 families and 34 women at risk of being carriers of Duchenne and Becker muscular dystrophies were analysed blind by restriction fragment length polymorphisms (RFLPs) and a new, non-radioactive direct test based on competitive polymerase-chain-reaction (PCR) amplification. All obligate carriers were correctly diagnosed by RFLPs and competitive PCR, and 7 women with a 99% risk of being carriers were also diagnosed carriers by competitive PCR. There were no false positives or false negatives. Only 1 PCR result was non-informative. Our test allows rapid, precise, and direct carrier diagnosis of women whose relatives have a known deletion of the dystrophin gene.

False Negative Reactions↗
PubMed1977

Modified Sutter's arginine dihydrolase medium for Pseudomonas speciation.

Sutter's arginine dihydrolase medium has been modified to obtain maximum yields of arginine dihydrolase. Bromothymol blue is the indicator for alkalinity in Sutter's medium. By adding glucose and lowering the pH of the medium, more positive reactions were obtained in 24 hr as well as a sharper color contrast to the base medium which facilitated reading the reactions. The modified Sutter's medium was included in the routine biochemical schema for speciation of pseudomonads isolated from cosmetic products. Of the 706 strains belonging to the 5 species isolated form cosmetic products, only one false negative reaction was obtained with a strain of Pseudomonas putida. The medium was also used for the biochemical characterization of 122 Pseudomonas sp. isolates.

Arginine↗
PubMed2001

Evaluation of T cell receptor testing in lymphoid neoplasms: results of a multicenter study of 29 extracted DNA and paraffin-embedded samples.

To evaluate current diagnostic methods used for the evaluation of T cell receptor (TCR) gene rearrangements, 24 different laboratories analyzed 29 lymphoid neoplasm samples of extracted DNA and paraffin-embedded tissue and were asked to complete a technical questionnaire related to the testing. Participating laboratories performed Southern blot and polymerase chain reaction (PCR) testing for rearrangements of the TCRbeta chain gene and PCR for the TCRgamma chain gene rearrangements. Of 14 laboratories performing TCRbeta Southern blot analysis, there was complete agreement in 10 of 14 cases, with some false negative results obtained in 4 cases. No false positive results were obtained by Southern blot analysis. TCRbeta PCR analysis was only performed by two laboratories, and only 47.1% of positive samples were detected. Twenty-one laboratory results were obtained for TCRgamma PCR. This method showed an overall detection rate of 77.9% for T cell gene rearrangements with a 4.1% false positive rate, as compared to both TCRgamma Southern blot analysis results and immunophenotyping. The detection rate for TCRgamma PCR, however, significantly differed when extracted DNA samples from frozen tissue were compared to paraffin-embedded tissue (85.4% versus 65.9%; P = 0.0005). Significant differences in true positive results were obtained when laboratories using primers directed against multiple TCRgamma variable regions (V1-8 plus one to three other primer sets) were compared to laboratories that used only a single set of TCR primers directed against the V1-8 (P < 0.0001). Other technical factors significantly affecting results were also identified. These findings provide useful data on the current state of diagnostic TCR testing, highlight the risk of false negative results for TCR testing directed against only portions of the TCRgamma gene, and identify limitations of testing of paraffin-embedded tissues in some laboratories.

Blotting, Southern↗
PubMed1994

Methods in pathology. An improved method for DNA diagnosis of leprosy using formaldehyde-fixed, paraffin-embedded skin biopsies.

To improve the sensitivity of the previously reported polymerase chain reaction (PCR) for the detection of Mycobacterium (M.) leprae in the formaldehyde-fixed, paraffin-embedded tissues, we adapted the PCR designed to amplify an internal 372 bp fragment of a M. leprae-specific repetitive sequence to 39 skin biopsies taken from patients with leprosy of the lepromatous type and tuberculoid type. Crude DNA samples were prepared from tissue sections that were deparaffinized and subjected to proteinase-K digestion without any further treatment for DNA purification. Overcoming a false-negative reaction by an elongation of the period for enzymatic digestion and an appropriate dilution of the samples, an amplification of the target sequence was obtained as a single band with all 39 skin biopsies tested. The fragments specifically amplified by the PCR were subjected to direct sequencing and were confirmed to be identical with an internal 372 bp of M. leprae-specific repetitive sequence. Although in nine of 24 nonleprosy control samples, a false-positive amplification was observed as from one to several bands, they were distinguishable from the specific one by the electrophoretic pattern. This PCR makes up for the classic histological methods used in the diagnosis of leprosy.

Base Sequence↗
PubMed1998

The value of anti-calretinin antibody in the differential diagnosis of normal and reactive mesothelia versus metastatic tumors in effusion cytology.

In effusion cytology the distinction of reactive mesothelia from metastatic carcinoma cells may be a diagnostic challenge. Immunocytochemistry using antibodies suitable to detect epithelial cells must be considered carefully due to limited sensitivity and specificity of these antibodies. Efficient results in histological differential diagnosis of malignant mesothelioma versus lung-adenocarcinoma applying a novel antiserum against the calcium binding protein calretinin inspirated us to investigate the value of anti-calretinin antibody in effusion cytology combined with an epithelial marker. Cytoslides prepared by cytocentrifugation from 42 malignant and 65 reactive effusion specimens were immunostained using antibodies against calretinin and the epithelial marker Ber-EP4. Positive immunoreaction for calretinin in normal and reactive mesothelial cells was noted in 93% of the cases, whereas immunoreaction for calretinin was completely negative in the metastatic cells in 95% of the malignant effusions. Metastatic carcinoma cells were detected with anti-Ber-EP4 in 83% of malignant effusions. Non-specific positive reactions for Ber-EP4 in single mesothelial cells were observed in 16% of all cases and, moreover, frequently with macrophages or neutrophilic granulocytes. Our results demonstrate high sensitivity and specificity of anti-calretinin antibody for mesothelial cells in effusion specimens. They support its application to improve the diagnostic reliability of epithelial markers, especially because anti-calretinin antibody could be helpful in the assessment of false positive and false negative reactions of epithelial markers.

Antibodies, Monoclonal↗
PubMed1976

Intradermal testing after severe histamine reactions to intravenous drugs used in anaesthesia.

In a series of patients who suffered severe histamine mediated reactions to induction agents and muscle relaxants, intradermal testing enabled the drug involved to be distinguished. The correct use of intradermal testing to give reliable results is discussed and a protocol described. Prausnitz Kustner testing was of little help in confirming the results. A number of patients tested showed high levels of immunoglobulin G (IgG) and it is believed that IgG mediated anaphylaxis may be the mechanism responsible for reactions that have been previously described as anaphylactoid or direct chemical histamine release.

Adult↗
PubMed1976

[Lymphocyte transformation test in Gell's and Coombs' drug reactions].

A method of interpretation of the lymphocyte transformation test is described which results on the basis of statistical evaluation. With this method good results were received in cases of drug induced side effects of type I according to Gell and Coombs. The investigations on 61 patients have shown that differneces between the clinical findings and lymphocyte transformation tests are rare. They are mainly in relation to false-positive reactions of the lymphocyte transformation test in Penicillin allergy.

Diagnostic Errors↗
PubMed1995

Robust nonradioactive oligonucleotide ligation assay to detect a common point mutation in the CYP2D6 gene causing abnormal drug metabolism.

A new nonradioactive oligonucleotide ligation assay for the detection of a common point mutation in the CYP2D6 gene is presented. The assay takes advantage of simultaneous time-resolved fluorescence measurements of lanthanide-labeled probes and the specificity of T4-DNA ligase in combination with the polymerase chain reaction. This strategy makes it possible to perform the assay using both the wild-type-specific and mutant-specific probes simultaneously, securing an internal control in each reaction. We show that the allele-specific ligation part of the assay can be performed with great accuracy over a wide range of temperatures, salt concentrations, and T4-DNA ligase concentrations. This eliminates the risk of false-positive or false-negative reactions due to variations in these factors. Because the assay is simple to perform, is very reliable, and can be partly automated, we conclude that it is well-suited for analysis in a routine laboratory.

Adenosine Triphosphate↗
PubMed1975

Use of different saprophytic acid-fast bacilli in complement-fixation test for kala-azar.

Complement-fixation tests for kala-azar using antigenic extracts from 4 different saprophytic acid fast bacilli were carried out. It was observed that all the 4 extracts gave positive reactions with sera from kala-azar patients. However, Myco. phlei gave best results and next comes Kedrowsky's bacilli. These two are different strains of the same organism, Myco. phlei. Myco. smegmatis also gave satisfactory results but Myco. butyricum gave weak and false negative reactions in some cases. Last two organisms are the different strains of the same Myco. smegmatis.

Antigens, Bacterial↗