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At least 307 records · Page 17Linked to original sources
PubMed1978

Pitfalls in the diagnosis of pericardial effusion.

Echocardiography has proven to be a sensitive and reliable technique in the diagnosis of pericardial effusion. Care must be taken in recording to maintain proper angulation of the transducer, to scan adequate sites, and to maintain proper gain settings. The following entities may mimic pericardial effusion and must be excluded by careful analysis: left pleural effusion, mitral annulus calcification, anterior mediastinal space-occupying lesions, fibrinous pericardial reactions, and right heart catheters. Care must also be taken in the quantitation of pericardial fluid and in hemodynamic extrapolation.

Calcinosis↗
PubMed1998

Evaluation of the RapID CB plus system for identification of coryneform bacteria and Listeria spp.

In a stress test, the recently introduced RapID CB Plus system (Remel Inc. [formerly Innovative Diagnostic Systems], Norcross, Ga.) was challenged with a diverse set of gram-positive rods comprising 345 strains of coryneform bacteria and 33 strains of Listeria spp. representing a total of 49 different taxa. Overall, within 4 h, the system correctly identified 80.9% of the strains on the species level and 12.2% of the strains on the genus level. Only 3.7% strains were misidentified, and for 3.2% of the strains no identification was provided. Difficulties with the system were mainly due to occasional uncertainties in reading reactions for acid production from carbohydrates and, to a lesser extent, aminopeptidase reactions. It is concluded that the system may also perform well under the conditions of a routine clinical laboratory.

Actinomycetales↗
PubMed1981

[The occult blood reaction].

The faecal benzidine assay has been replaced during the last few years by a great number of different assays on occult blood in faeces. The causes of occult blood at children are different from adults. Which test should be used depends on the desired sensitivity of 2 à 3 mg haemoglobin/g faeces are most suitable to prevent false-positive and false-negative results. To reduce false-negative results it is recommended to perform the assay on three successive days.

Child↗
PubMed1977

Diagnosis of Hymenoptera hypersensitivity by skin testing with Hymenoptera venoms.

This double-blind study provides evidence that skin testing with dialyzed Hymenoptera venoms is a more accurate, reliable method of diagnosing hypersensitivity to the sting of honeybee, yellow jacket, yellow hornet, white-faced hornet, and wasp than is skin testing with the corresponding whole body diagnostic allergenic extract. Furthermore, the incidence of false-positives was greatly reduced by using the dialyzed Hymenoptera venom (HDV) diagnosis. In this clinical trial, most sensitive individuals had skin test reactions greater than the diluent control at concentrations of 1 mug/ml or below. Levels of venom diagnostic of 100 mug/ml appeared to produce nonspecific local irritation. Skin test with whole body diagnostic allergenic extract did not produce a consistent differentiation between sensitive and nonsensitive individuals. No untoward reactions were seen using the dialyzed Hymenoptera venom (HDV) diagnostic.

Animals↗
PubMed1993

Use of jacalin as a solid phase in ABO reverse grouping.

A major problem of using red cells as the solid phase in assay systems is the difficulty to bind them strongly to appropriate surfaces. We report here on a number of lectins of different specificities which were examined for their ability to bind red cells to polystyrene 96-well microtitre plates. The use of the Thomsen-Friedenreich antigen-specific lectins, jacalin, mushroom and Maclura pomifera agglutinin proved the most useful for ABO reverse grouping. Jacalin-coated plates were also compared with plates coated with poly-L-lysine and bovine serum albumin/glutaraldehyde for the binding of erythrocyte membranes and were found to be superior. We also describe the colorimetric detection of the solid phase red cell antibody reaction by using an indicator erythrocyte and peroxidase chromogenic substrate.

ABO Blood-Group System↗
PubMed1989

A comparison of six epicutaneous devices in the performance of immediate hypersensitivity skin testing.

Six devices commonly used for immediate hypersensitivity epicutaneous skin testing were compared with regard to precision and diagnostic accuracy. Fifteen subjects were tested on the back to 10 mg/ml of histamine phosphate and 50% glycerosaline by prick technique with a smallpox needle (SN), bifurcated needle (BN), Greer "pen" (GP), and blood lancet, and by puncture with the Morrow-Brown needle (MB) and Multi-Test (MT). Five devices were tested in quintuplicate to histamine and once to glycerosaline in each subject; with MT, five histamine and three glycerosaline sites were used. Analysis of the wheal areas obtained with SN, BN, GP, and MB demonstrated comparable degrees of precision (coefficient of variation). The precision of MT was less than the other devices (p less than 0.05). The blood lancet demonstrated intermediate precision. Twenty-two of 45 (49%) of the glycerosaline skin tests performed with MT were falsely positive, significantly more than the other devices (p = 0.0001). We conclude that MB, BN, GP, and SP are comparable devices for use in immediate hypersensitivity skin testing. The low precision and reliability of MT used for testing on the back would appear to make this device less than adequate for diagnostic or research studies. Its high rate of false positive reactions requires caution in interpretation of results when it is used in the clinical diagnosis of allergy.

Adult↗
PubMed1982

0.1% triamcinolone acetonide ointment and patch test responses.

The effect of topical steroids on patch test responsiveness was investigated in 15 subjects. A 0.1% triamcinolone acetonide ointment and a control preparation were applied three times daily to opposing sites on the upper part of the inner arms prior to patch testing. From a total of 18 pairs of patch tests applied to the 15 patients, substantial differences in the paired reactions were seen in only three patients after 96 hours. Of these, two had the more intense reaction on the control side, and the third had a greater reaction on the triamcinolone-pretreated side. Previously applied, intermediate-strength topical steroids are unlikely to prevent the detection of contact allergy by patch testing.

Dermatitis, Contact↗
PubMedDate not supplied

Peroxidase reaction as a parameter for discrimination of Streptococcus mutans and Streptococcus sobrinus.

425 strains of mutans streptococci and 12 reference strains were investigated by membrane fatty acid spectra (MFAS) and peroxidase reaction (PR) after aerobic and anaerobic incubation. 423 strains were identified as Streptococcus mutans. The remaining 2 strains were identified as Streptococcus sobrinus. The PR of 29 strains was doubtful; immediately after anaerobic incubation a negative PR changed into a slightly positive PR. To test the diagnostic value of PR the strains were additionally investigated by means of species-specific polymerase chain reactions (PCR). The species-specific PCRs were developed on the basis of the respective genes of 16S rRNA of the pathogens S. mutans and S. sobrinus. Specificity and sensitivity were tested on reference strains (n = 17) and negative control strains (n = 39). The results of this investigation showed that an anaerobic incubation regime could lead to false-positive (S. mutans) or false-negative (S. sobrinus) PR. The 425 MS strains were classified as either S. mutans (n = 420) or S. sobrinus (n = 5). The findings on the reference strains required a reclassification of S. mutans V 100 into S. sobrinus V 100. Summarising, it is possible now to differentiate strains of mutans streptococci by MFAS and PR after aerobic incubation.

Aerobiosis↗
PubMed1996

Evaluation of two commercial microtiter cytotoxin assays for the detection of Clostridium difficile toxin B in stool specimens.

Two commercial microtiter cytotoxin assays using a fibroblast cell line (Bartels, Baxter Diagnostics, Inc., Deerfield, IL) and an epithelial cell line (Cytotoxi Test, Advanced Clinical Diagnostics, Toledo, OH) were evaluated for their ability to detect Clostridium difficile toxin B in stool specimens. After 48 hours, the assays had comparable sensitivity (90 versus 92%) and specificity (99 versus 98%). Although not statistically significant, the Bartels assay detected more toxin-positive specimens at 24 hours (84 versus 72%, P = 0.089, Fisher's Exact Test) and the Cytotoxi assay had fewer nonspecific reactions requiring repeat testing (2.2 versus 1.1%, P = 0.186, Fisher's Exact Test). Both cytotoxin assays had comparable analytic performance.

Biological Assay↗
PubMed1981

Immunodiagnosis of recently acquired Schistosoma mansoni infection. A comparison of various immunological techniques.

A group of Dutch tourists, who became infected with Schistosoma mansoni in Ethiopia, was investigated in a serological follow-up study, during 8-50 weeks after infection. The following immunodiagnostic tests were applied: (1) the immunofluorescent antibody (IFA) test, both on frozen sections of adult worms, and in a modification for the detection of antibodies against gut-associated polysaccharide antigens; (2) the enzyme-linked immunosorbent assay (ELISA) with as antigens: adult worm antigens (AWA), cercarial antigens (CA), soluble egg antigens (SEA), and the purified antigens CAA and MSA1; (3) the defined antigen substrate spheres system with AWA as antigen in an immunofluorescence and immunoperoxidase modification; (4) the indirect haemagglutination reaction with AWA; and (5) the immunoelectrophoresis with AWA and antigens of the intermediate host. With these techniques it could be shown that in all persons which had been in contact with S. mansoni infected water, also in those not excreting schistosome eggs or not showing clinical symptoms of infection, specific anti-schistosome antibodies were present. No false-negative reactions were found with the ELISA with cercarial antigens, MSA1, or AWA-TCA, with the IFA detecting gut-associated polysaccharide antigens and with the immunoelectrophoresis. The highest titres were observed with the two techniques (IFA and ELISA) detecting antibodies against the gut-associated polysaccharide antigen CAA.

Enzyme-Linked Immunosorbent Assay↗
PubMed1996

False-positive polymerase chain reaction results for human papillomavirus in lichen planus. Potential laboratory pitfalls of this procedure.

BACKGROUND: The polymerase chain reaction (PCR) is a common tool in laboratory evaluation of tissue samples. It has been particularly useful in testing for nucleic acids of infectious organisms implicated in the pathogenesis of cutaneous diseases. OBJECTIVE: Our purpose was to evaluate archival biopsy material (paraffin-embedded) of lichen planus for human papillomavirus (HPV) DNA with PCR and in situ hybridization (ISH). METHODS: Tissue sections were obtained from 13 specimens of lichen planus and 10 control tissues. Standard methods for PCR and ISH were used to evaluate the presence of HPV DNA. RESULTS. Initial PCR results demonstrated HPV DNA in 11 of 13 specimens and in none of the control tissue. However, testing for specific HPV types revealed nucleic acid contamination. ISH was negative in all specimens. CONCLUSION: Accurate evaluation of tissue with PCR is difficult because of the procedure's profound sensitivity. Positive results reported in the literature should be viewed with caution. Potential causes for false-positive and false-negative results should be considered.

Biopsy↗
PubMed2002

Prediction of fetal Rh D and Rh CcEe phenotype from maternal plasma with real-time polymerase chain reaction.

Real-time PCR methods for the detection of RHD and the C, c, and E allele of RHCE were applied for the prediction of fetal Rh phenotype using maternal plasma. In one of 36 samples investigated the DNA extraction failed. When we tested the remaining 35 samples for Rh antigens which were absent on the mother's red cells, the fetal D-status was correctly determined in 26 of 27 cases (1 false negative). Fetal C was tested correctly in 23 samples, c was true positive in the only c-negative woman and the fetal E-status was correctly determined in 35 cases. In conclusion real-time PCR of maternal plasma is a non-invasive method to determine fetal RH genotype. However, more studies are required for routine applications because the method is not 100% sensitive.

Alleles↗
PubMed1989

Lack of specificity of Chlamydiazyme for detection of vaginal chlamydial infection in prepubertal girls.

A 1-year prospective study was undertaken of 65 prepubertal girls referred for evaluation of sexual abuse or vulvovaginitis to compare Chlamydiazyme, an enzyme immunoassay (EIA), with culture for the detection of Chlamydia trachomatis i in vaginal specimens. Five (8%) of 65 patients were initially EIA-positive. On repeat sampling without intervening antibiotic treatment, 4 girls who were initially positive became negative and 1 remained persistently positive. Chlamydial cultures were negative in all patients. The patient with the persistently positive EIA also had Group A streptococcal vaginitis. We were able to demonstrate that some strains of Group A Streptococcus can cause a positive reaction with the EIA. Cross-reactions with other bacterial species are also known to occur. We therefore conclude that Chlamydiazyme is not specific for the detection of chlamydial infection in the vagina of prepubertal girls and, for medicolegal reasons, should not be used for evaluation of sexual abuse.

Antigens, Bacterial↗
PubMed1978

[Applications and limitations of immunological techniques in the sero-epidemiological analysis of parasitic risk (author's transl)].

In order to be applicable to sero-epidemiology, serological reactions must lend themselves to micro-techniques and automation. Their results, notably concerning malaria, sleeping sickness, amoebiasis, schistosomiasis and filariasis, complement those of direct parasitological examination. Serology is often more accurate, but is also more costly and should be reserved for those cases in which other analytical methods are either impossible or too undependable (low transmission level). Serological methods generally involve little risk or false negativity, but they can be falsely positive and improvement of the specificity of available testing procedures is at present one of the major technological problems of parasitic sero-epidemiology.

Amebiasis↗
PubMed1992

Evaluation of the Multi-Test device for immediate hypersensitivity skin testing.

Test-to-test reproducibility, user variability, and the effect of positive reactions on adjacent negative sites were evaluated for the Multi-Test skin testing device. Twenty-five subjects had skin tests with 24 histamine (1 mg/ml), four glycerosaline controls, and four "dry" controls on two testings 7 days apart. To assess reproducibility from large and smaller histamine reactions and/or their effect on adjacent negative controls, 10 of the 25 subjects were retested once with the same testing format, but histamine at 10 mg/ml was substituted. To determine whether large allergen reactions affect adjacent negative controls differently than histamine reactions, 24 additional patients were retested on arms and back with negative controls adjacent to allergens to which they had prior 3+ to 4+ skin test reactions. Conclusions from 2688 skin tests on 49 patients are as follows: large (mean > 10 mm) histamine reactions reproduced better than smaller (mean < 7 mm) responses--coefficients of variation were 12.3 and 21.4 respectively. A 14% user variability occurred when comparing mean wheal sizes from histamine produced by each nurse and 1.2% when comparing their coefficients of variation. Neither small histamine reactions nor large reactions from histamine and allergens affected adjacent negative controls. We conclude that Multi-Test is a highly reliable skin testing technique that provides good reproducibility of results and low user variability.

Adolescent↗
PubMed2005

TASK-3 immunoreactivity shows differential distribution in the human gastrointestinal tract.

The presence and distribution of TASK-3 immunopositivity (a channel with potential oncogenic significance) was investigated in the human gastrointestinal system. The immunohistochemical reactions were performed with two commercially available polyclonal antibodies, targeting different epitopes of the channel protein. Experiments conducted on frozen and formalin-fixed samples indicated that the application of a suitable antigen retrieval (AR) technique was essential to produce consistent, strong and reproducible TASK-3-specific immunolabelling of the formalin-fixed tissue. The lack of or inappropriate selection of the AR resulted in false-negative reactions. As for the distribution of the TASK-3 channels, strong immunolabelling was observed in the gastric and large intestinal mucosa, with particularly prominent immunoreactivity of the epithelial cells. In contrast, the smooth-muscle layers demonstrated weak TASK-3 positivity. Intense TASK-3 expression was noted in both the exocrine and endocrine pancreas, but the islets of Langerhans exhibited more powerful reactions. The ductal apparatus of the submandibular gland and lymphocytes situated in pericolonic lymph nodes were also TASK-3 positive. Strong TASK-3 positivity could also be observed in malignant gastrointestinal tumours, with intense nuclear-perinuclear labelling of some of the tumour cells. The present findings suggest that TASK-3 channels may have roles in the gastrointestinal functions, including insular hormone secretion.

Biomarkers↗
PubMedDate not supplied

Protein precipitation as a possible important pitfall in the clinical chemistry analysis of blood samples containing monoclonal immunoglobulins: 2 case reports and a review of the literature.

Two case reports are presented, both illustrating an analytical interference caused by monoclonal immunoglobulins. Falsely low results were obtained in the routine analysis of glucose, CRP and HDL-cholesterol. When analysing samples containing paraproteins, various problems can be encountered in the clinical laboratory: next to the antibody effect, pseudohyponatraemia, hyperviscosity, cryoglobulinaemia and gel formation have to be taken into account. In our two cases the interference was caused by paraprotein precipitation, causing an increased turbidity and an apparent increase of light absorbance at every wavelength due to light scattering, including the wavelengths used in the clinical chemistry assays. We review the literature on this sometimes overlooked interference in photometric/turbidimetric assays. This reaction is based on the insolubility of these proteins in specific physico-chemical circumstances in which many variables are involved, among others: pH and ionic strength, presence of preservatives and surfactants in the assays, pI and other specific properties of the monoclonal immunoglobulins. The complexity of the problem makes predicting or preventing this probably infrequent interference usually impossible. This artifact can cause both false positive and false negative results in multiple parameters (e.g. bilirubin, creatinine, iron, urea, uric acid), the most frequently reported analyte being phosphate. The Sia water test (Sia euglobulin precipitation test) can provide a first clue to a paraprotein aggregation; confirmation can be obtained by observing the time/ absorbance curves of the analysis, performing the test manually or setting up a serial dilution of the sample. The problem can be solved by avoiding the presence of the proteins in the assay, performing the analysis using an alternative method or diluting out the interference. Both laboratorians and clinicians should be aware of interferences in the clinical laboratory since the clinical consequences could be important.

Aged↗
PubMedDate not supplied

IUPAC collaborative trial study of a method to detect genetically modified soy beans and maize in dried powder.

This paper presents results of a collaborative trial study (IUPAC project No. 650/93/97) involving 29 laboratories in 13 countries applying a method for detecting genetically modified organisms (GMOs) in food. The method is based on using the polymerase chain reaction to determine the 35S promotor and the NOS terminator for detection of GMOs. reference materials were produced that were derived from genetically modified soy beans and maize. Correct identification of samples containing 2% GMOs is achievable for both soy beans and maize. For samples containing 0.5% genetically modified soy beans, analysis of the 35S promotor resulted also in a 100% correct classification. However, 3 false-negative results (out of 105 samples analyzed) were reported for analysis of the NOS terminator, which is due to the lower sensitivity of this method. Because of the bigger genomic DNA of maize, the probability of encountering false-negative results for samples containing 0.5% GMOs is greater for maize than for soy beans. For blank samples (0% GMO), only 2 false-positive results for soy beans and one for maize were reported. These results appeared as very weak signals and were most probably due to contamination of laboratory equipment.

Agrobacterium tumefaciens↗