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Results for “False Positive Reactions”

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PubMed1987

Four-year follow-up of psychological reactions to false positive screening tests for congenital hypothyroidism.

Thirty-two families were investigated four years after a false alarm in the neonatal screening of their newborns. Sixteen of the families showed signs of persistent anxiety 6-12 months after the screening. Thirteen of them still show anxiety after 4 years. Of the 16 without anxiety at 6-12 months, 6 show signs of anxiety now. This persistent anxiety may be related to the initial psychological trauma of the false positive screening result. Thus, 19 of the 32 families have not completely integrated their experience. Twenty-four children were psychologically evaluated. Eight families refused to have their children examined. Twelve of the children showed disturbed behavior, 10 of these have parents who show unsatisfactory integration. Medical measures have psychological side-effects, which may be interpreted as iatrogenic. However, the effects of an external stress depend on the individual's susceptibility to it and abilities to cope with it and use external support available.

Anxiety↗

PubMed2005

Specificity dependence between serological tests for diagnosing bovine brucellosis in Brucella-free farms showing false positive serological reactions due to Yersinia enterocolitica O:9.

When brucellosis false positive serological reactions happen in cattle, the serial use of pairs of specificity-correlated serological tests (rose bengal, complement fixation, competitive ELISA) results in specificities lower than expected. In this situation, highly specific tests, such as the indirect ELISA used alone, may be more adequate than serial testing.

Agglutination Tests↗

PubMed1988

Evaluation of excretory-secretory antigens for the serodiagnosis of swine trichinellosis.

Groups of hog sera from endemic and non-endemic areas for swine trichinellosis in Yugoslavia were tested by ELISA using excretory-secretory (ES) antigens collected from T. spiralis muscle larvae maintained in vitro for 24, 48 or 72 h. The 24-h ES had the highest level of specificity for T. spiralis infection. Antigen preparations recovered after 48 or 72 h yielded an increasing rate of false-positive reactions. Additional antigens occurred in the 48- and 72-h ES preparations as determined by gel electrophoresis and monoclonal antibody binding. The occurrence of false-negative reactions was directly correlated with T. spiralis worm burdens. Hogs with muscle larvae densities greater than 10 larvae per gram were all positive by ELISA. Among 17 hogs with less than 10 larvae per gram, only one hog was negative by ELISA with 24-h ES antigen; the false-negative rate was higher with 48- and 72-h ES. These results show that ES antigen produced during the first 24 h of in vitro cultivation is highly specific for the immunodiagnosis of swine trichinellosis.

Animals↗

PubMed1991

Evaluation of a rapid fluorogenic method for the detection of Escherichia coli in dairy products.

A rapid fluorogenic medium was evaluated for the detection of Escherichia coli in dairy products. The medium was capable of detecting Esch. coli after 7.5 h incubation at 41.5 degrees C. Samples of pasteurized milk (136), raw milk (63), soft cheese (60) and pasteurized cream (39) were examined with media based on 4-methylumbelliferyl-beta-D-glucuronide (MUG-7) and Violet red bile agar and there were no significant differences between the numbers of Esch. coli detected on the two media. MUG-7 medium had a specificity of 98.6% and the small number of organisms giving a false positive reaction were identified as Klebsiella pneumoniae. The incidence of false negative results was approximately 2%. MUG-7 medium was suitable for pour plate, spread plate and membrane filtration methods. Possible applications of the method are discussed.

Animals↗

PubMed1994

False positive widal reaction in high-titer disseminated BCG infection.

False-positive Widal reactions following certain non-typhoid Salmonella infections may occur commonly. The case of a patient who developed miliary tuberculosis secondary to intravesical bacillus Calmette-Guérin (BCG) immunotherapy for bladder carcinoma is described. Very high titers of typhoid and paratyphoid agglutinins were obtained with the Widal test; these titers returned to normal after successful anti-tuberculous treatment. This case of high-titer, false-positive Salmonella typhi and Salmonella paratyphi A and B reactions to BCG infection occurred in an area non-endemic for typhoid or paratyphoid fever.

Agglutination Tests↗

PubMed1977

The use of preserved milk samples in the Brucella milk ring test.

Brucella milk ring tests (BMRT's) were performed on fresh herd milk samples and pooled samples, preserved at a processing factory with potassium dichromate. Preserved milk from samples pooled over a 10-day period, gave results that were similar to an average result for individual fresh daily samples over the same period. When fresh samples gave variable results and the pooled preserved sample gave a negative result, it was considered that the latter result was more reliable, possibly due to factors causing false positive reactions being diluted. Blood testing of herds for circulating antibody indicated that the use of either fresh or preserved milk samples could occasionally produce false negative or false positive results.

Agglutination Tests↗

PubMed1990

Assessment of an enzyme-linked immunosorbent assay using a Taenia hydatigena fraction antigen in the diagnosis of cysticercosis in cattle.

Enzyme linked immunosorbent assay (ELISA) using a fraction of larval Taenia hydatigena cyst fluid antigen was carried out on 469 bovine sera collected at slaughter from feedlot cattle for the presence of anticysticercosis antibodies. Cysticerci, in low numbers, were found in the heart, tongue and/or masseter muscles of 84 of the 469 cattle at postmortem inspection. Only nine sera gave positive ELISA reactions and in only one of these nine animals were cysticerci found. Within the limitations of this study, the high rate of false negative and false positive reactions suggests that the ELISA with the antigen used is not a satisfactory procedure to diagnose cysticercosis in cattle, at least in animals with light infections.

Animals↗

PubMed1989

Evaluation of four qualitative methods for detection of beta-lactamase production in Staphylococcus and Micrococcus species.

Four qualitative methods for the detection of beta-lactamase production in Staphylococcus and Micrococcus species were evaluated and compared with a quantitative macroiodometric reference method. The disc diffusion test with penicillin G and the cloverleaf method could not separate beta-lactamase-positive from beta-lactamase-negative strains. Two applications of the chromogenic cephalosporin test, using uninduced strains and strains grown on blood agar plates, gave a large number of false negative and false positive results. False negative reactions were most common among uninduced strains, while the false positive reactions were most often recorded for Staphylococcus saprophyticus. A high degree of efficiency was recorded for the nitrocefin spot test, using induced strains grown on antibiotic susceptibility agar, and for the starch-iodine plate method. The starch-iodine plate with methicillin as inducer gave the most reliable results.

Bacteriological Techniques↗

PubMed1980

Single tube confirmatory tests for Escherichia coli.

In a multi-laboratory trial, lauryl tryptose mannitol broth (LTMB) and minerals-modified glutamate medium with added tryptophan (MMGM + T) were compared as single tube tests for the confirmation of Escherichia coli in water; the confirmed results were also compared with the production of gas from minerals-modified glutamate medium without added tryptophan (MMGM). LTMB and MMGM + T gave similar gas and indole results with about 90% of the water samples in most of the laboratories. When compared with the 'correct' results as judged by acid and gas production from lactose peptone water and indole from tryptone water, the difference in the rate of false positive reactions between LTMB and MMGM + T was insignificant; but LTMB gave a significantly lower rate of false negative reactions than MMGM + T. Gas production from MMGM without added tryptophan gave significantly higher rates of both false positive and false negative reactions. Lauryl sulphate is therefore a suitable inhibitory surfactant for use in single tube media for the confirmation of E. coli, which can be recommended.

Bacteriological Techniques↗

PubMed1987

Monitoring of dairy herds for Brucella abortus infection when prevalence is low.

A total of 2,698 dairy herds were surveyed in 1981-1982 in New South Wales and north eastern Victoria in a review of the methods used to monitor them for the presence of Brucella abortus. The methods used to monitor dairy herds were testing of all breeding cows over 1 year of age using the rose bengal test (RBT) and complement fixation test (CFT), the bulk milk ring test (BMRT), and testing of blood samples collected at abattoirs using the RBT and CFT. The surveyed herds had at least one whole herd test, and BMRT was done at regular intervals in the period of the survey. Of the 99 (3.7%) herds that reacted to the BMRT, 91 (3.4%) herds had false positive reactions and 8 (0.3%) herds were declared infected on follow-up herd testing. False-positive reactions were obtained in 22 herds on more than one occasion. Common causes of false positive reactions to the BMRT were thought to be previous vaccination with Strain 19 and sampling in very early or late lactation. Of the 98 (3.63%) herds that reacted to the whole herd serological tests, 80 (2.96%) herds had false-positive reactions and 18 (0.67%) herds were declared infected. Strain 19 vaccination was thought to be an important cause of false-positive reactions. Fifty-three (2.0%) herds showed suspicious reactions on abattoir monitoring but none was declared infected on follow-up testing. Of the 18 herds with infected or equivocal status, the BMRT identified?(ABSTRACT TRUNCATED AT 250 WORDS)

Abattoirs↗

PubMed2002

The Dutch Brucella abortus monitoring programme for cattle: the impact of false-positive serological reactions and comparison of serological tests.

The Dutch national Brucella abortus eradication programme for cattle started in 1959. Sporadic cases occurred yearly until 1995; the last infected herd was culled in 1996. In August 1999 the Netherlands was declared officially free of bovine brucellosis by the European Union. Before 1999, the programme to monitor the official Brucella-free status of bovine herds was primarily based on periodical testing of dairy herds with the milk ring test (MRT) and serological testing of all animals older than 1 year of age from non-dairy herds, using the micro-agglutination test (MAT) as screening test. In addition, serum samples of cattle that aborted were tested with the MAT. The high number of false positive reactions in both tests and the serum agglutination test (SAT) and complement fixation test (CFT) used for confirmation seemed to result in unnecessary blockade of herds, subsequent testing and slaughter of animals. For this reason, a validation study was performed in which three indirect enzyme-linked immunosorbent assays (ELISAs), the CFT and the SAT were compared using a panel of sera from brucellosis-free cattle, sera from experimentally infected cattle, and sera from cattle experimentally infected with bacteria which are known to induce cross-reactive antibodies (Pasteurella, Salmonella, Yersinia, and Escherichia). Moreover, four ELISAs and the MRT were compared using a panel of 1000 bulk milk samples from Brucella-free herds and 12 milk samples from Brucella abortus- infected cattle. It is concluded that the ELISA obtained from ID-Lelystad is the most suitable test to monitor the brucelosis free status of herds because it gives rise to fewer false-positive reactions than the SAT.

Agglutination Tests↗

PubMed1990

Evaluation of a synthetic peptide-based assay and a rapid dot-blot recombinant test for detection of antibodies to HIV-1 and HIV-2.

Our objective was to evaluate two new serologic assays for detecting HIV-1 and HIV-2 positive and negative sera. A total of 154 human sera from African countries were tested using a synthetic peptide-based passive hemagglutination assay (PHA) and a rapid dot-blot recombinant test (Test-Pack), both of which are marketed as HIV-1/HIV-2 combination assays. Results indicated that the PHA identified all HIV-1 and HIV-2 positive sera, although some were only weakly reactive. It produced one false positive reaction. The Test-Pack correctly detected all positive and negative sera, although several negative sera produced extremely weak reactions. Both tests detected two HIV-2 positive sera which were non-reactive by HIV-1 screening assays.

Evaluation Studies as Topic↗

PubMed1988

The case for patch test readings beyond day 2. Notes from the lost and found department.

Additional patch test readings taken after 2 days (48 hours) are valuable in distinguishing false-positive reactions, which may occur up to 22% of the time. Second readings taken on days 3 through 7 may detect an additional 34% positive reactivity. Those reactions, both lost (initially positive, later negative) and found (initially negative, later positive) by delayed readings, require clinical correlation for relevance as do the readings that persist at and beyond day 2 (positive at both readings).

Allergens↗

PubMed1992

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↗

PubMed1988

Chicken antibodies: a tool to avoid false positive results by rheumatoid factor in latex fixation tests.

19 rheumatoid factor (RF)-positive sera (Waaler-Rose test) and ten control sera were tested in latex agglutination. All RF-positive sera agglutinated latex particles coated with the different mammalian IgGs (cow, horse, human, mouse, sheep and rabbit) and with chicken anti-human C3 (which was used as a positive control), but none of them with non-specific chicken IgG. The control sera were all negative except when tested with chicken anti-human C3. Chicken antibodies should therefore be useful in assays were RF could interfere and give false positive reactions (e.g., nephelometry, latex agglutination or ELISA).

Animals↗

PubMed1970

Studies towards the standardization of lepromin. Progress and prospects.

Because of the wide range of concentrations of Mycobacterium leprae in existing lepromins the authors studied methods of producing a standardizable lepromin containing 160 million bacilli/ml. The effects of using different dilutions of lepromin on the incidence of false-positive reactions were also studied.Progress reported includes a convenient method for preparing large batches of non-sedimenting lepromin, which is directly suitable for microscopic counting of Myco. leprae cells; and a validation of current methods for microscopic enumeration of Myco. leprae. Skin tests with diluted lepromins have demonstrated that dilutions up to 1:16 increase progressively the ability to distinguish between lepromatous and tuberculoid leprosy. This work has provided further evidence that 20 million bacilli/ml (a 1:8 dilution of the initial lepromin) should produce adequate Mitsuda reactions in general populations, provided that 3-mm reactions are taken as the criterion for 1+ positivity. The net effect of these findings is equivalent to expanding the world supply of lepromin by 8 times.Recommendations for further research are proposed.

Antigens↗

PubMed2005

Evaluation of western blot CagA seropositivity in Helicobacter pylori-seropositive and -seronegative subjects.

CagA seropositivity is an important risk factor for gastric adenocarcinoma and duodenal ulcer. However, CagA seropositivity is also found in Helicobacter pylori-seronegative subjects. Is CagA seropositivity in these subjects a sign of a past H. pylori infection, or does it represent a false-positive reaction? This study investigates the intensity of the CagA immune reaction and the variation in CagA seroprevalence with year of birth for 650 subjects belonging to the Malmo Preventive Medicine cohort. CagA and H. pylori seroprevalences were determined by Western blot analysis (Helicoblot 2.1) and enzyme-linked immunosorbent assay. The peak intensity of the CagA band was significantly lower in H. pylori-seronegative subjects than in those with concomitant H. pylori seropositivity. In H. pylori-seropositive subjects, peak CagA intensity had a bimodal distribution. The prevalence of CagA-seropositive but H. pylori-seronegative subjects increased successively and significantly with year of birth, in contrast to the prevalence of CagA-seropositive and H. pylori-seropositive subjects, which decreased significantly. However, within H. pylori-seropositive and -seronegative subgroups, CagA seroprevalences were constant for different birth cohorts. If CagA seropositivity in H. pylori-seronegative subjects represents a past H. pylori infection, there must have been some mechanisms of eradication that were more common in younger subjects and that were of more importance than the presence of gastric atrophy and the longer duration and higher prevalence of H. pylori infection found in older subjects. Antibiotic treatment of H. pylori was not common practice at the time of enrollment. On the other hand, a false-positive reaction would be constant and independent of birth cohorts, as with the H. pylori-seronegative subgroup of our study. Peak CagA intensity in H. pylori-seronegative subjects corresponded to the lower part of the bimodal distribution of peak CagA intensity in H. pylori-seropositive subjects. We conclude that a major proportion of CagA seropositivity in H. pylori-seronegative subjects represents a false-positive reaction. Peak CagA intensity has a bimodal distribution in H. pylori-seropositive subjects. Low-intensity CagA seropositivity in H. pylori-seropositive subjects is indeterminate, representing both false-positive and true-positive reactions.

Adult↗

PubMed1987

[Causes of error in the study of fibrinogen clumping and the diagnosis of Staphylococcus aureus: Micrococci and Acinetobacter].

Rapid presumptive identification of S. aureus, particularly on the agar slant of biphasic blood culture bottles can be performed by modified slide clumping factor tests. We compared two commercial reagents (Staphyslide and Staphaurex) using strains of "Gram-positive cocci arranged in clusters" (S. aureus, S. epidermidis, Micrococcus) or diplococci-like organisms such as Acinetobacter. Micrococcus and Acinetobacter can be responsible for false-positive reactions with sensitized or not sensitized particles. Control reactions with not sensitized particles or autoagglutination tests in water rather than saline must be performed.

Acinetobacter↗