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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↗

PubMedDate not supplied

Comparison of three techniques for the detection of antibodies to double-stranded DNA: immunofluorescence on Trypanosoma gambiense, immunofluorescence on Crithidia luciliae and radioimmunoassay using the Farr technique.

Three techniques for the detection of antibodies against double-stranded DNA were compared: two immunofluorescent (IF) techniques using either Trypanosoma gambiense or Crithidia luciliae as antigen and a radioimmunoassay (RIA) based on the Farr technique. The IF on T. gambiense or C. luciliae gives very similar results but the reaction on C. luciliae is easier to read and to interpret. The use of C. luciliae permits the swift elimination of the two main causes of errors: antibodies against the nucleus of Trypanosomidae and antibodies reacting with the base of the flagella. The RIA appears as a very sensitive test since six sera gave a positive reaction with the RIA and a negative reaction with the IF on C. luciliae. However, the RIA gives in nine cases false positive reactions and in four cases false negative results. Those last four sera contained specific antibodies with low avidity for double-stranded DNA.

Animals↗

PubMed1977

The use of bovine PPD tuberculin the single caudal fold test to detect tuberculosis in beef cattle.

The efficiency of 2 different doses of bovine PPD tuberculin was compared using the caudal fold test for the detection of tuberculosis in beef cattle. Two matched groups of 98 cattle were selected on the basis of their reactivity to HCSM tuberculin. Cattle in each group were tested with a singl 0.1 ml dose of bovine PPD tuberculin containing either 0.1 mg or 0.2mg bovine PPD respectively. Two further groups of 100 young stock from a herd with an incidence of tuberculosis of less than 0.1% were selected as controls. Tests were interpreted subjectively by palpation and observation and objectively by caliper measurement at 48, 72 and 96h. All cattle were examined post mortem for the presence of visible lesions. The 0.2 mg dose of PPD detected 95% tuberculous cattle and caused false-positive reactions in 19% of cattle without lesions. The 0.1 mg dose detected 80% of tuberculous cattle and caused 11% false-positive reactions. No visible lesions of tuberculosis were found in either of the control groups although 11% reacted to 0.2 mg and 5% to 0.1 mg bovine PPD at 72h. The optimum time for reading tuberculin tests was found to be in the period 48 to 72h after the injection of bovine PPD and subjective interpretation was more efficient than caliper measurement as a means of detection of tuberculous cattle. The 0.2 mg dose of bovine PPD was found to be more specific than HCSM tuberculin.

Animals↗

PubMed1978

[Irregular antibody screening by Groupamatic at the Paris (C.N.T.S.) and Toulouse (C.R.T.S.) blood transfusion centers].

We report here the experience of 3 years of irregular antibody automated screening with Groupamatic, that is to say of 661,511 samples tested in Paris and 269, 162 samples tested in Toulouse. The positive reactions in Paris were 16,296 (2.46%) out of which 2,021 irregular antibodies were identified (0.30%). The positive reactions in Toulouse were 8,266 (3.07%) out of which 2,138 irregular antibodies were identified (0,79%). The difference between the number of screened positive reactions and the identified one is due to false positive reactions (half of the cases) and to autoantibodies whose number is roughly the same than the number of identified alloantibodies. During the years 1970, 1971 and 1972, the irregular antibodies were systematically screened in Toulouse on all blood donors with a manual technique on opaline plate using enzyme treated red cell tests (papain). 7,147 positive reactions were detected, out of 240,080 tests (2.98%). 1,954 (0,81%) were alloantibodies and 1,529 (0.64%) autoantibodies; 3.455 were false positive reactions and 209 were non identified antibodies. These figures are superimposed with those obtained with Groupamatic during the following years, thus pointing out the interest of this equipment.

Autoanalysis↗

PubMed1979

Cell-mediated immune responses in cattle adult-vaccinated with Brucella abortus strain 19 and in cattle infected with Brucella abortus field strain.

Cell-mediated immune responses in cattle adult-vaccinated with Brucella abortus strain 19, cattle infected with B abortus field strain, and nonexposed cattle were studied by an in vitro lumphocyte-stimulation test (LST). Lymphocytes were prepared from peripheral bovine blood by the Ficoll-diatrizoate technique, and results were assayed for [3H]thymidine incorporation into DNA by liquid scintillation spectrometry. Serotests and bacteriologic isolation attempts were conducted simultaneously with LST. Lymphocytes from cattle infected with field strains had significantly (P = 0.01) higher specific lymphocyte-stimulation inexposed controls. The LST, the serum standard-tube agglutination test (STT), the Rivanol (RIV) test, and the complement-fixation (CF) test correctly classified cattle from which field strains and strain 19 of B abortus were isolated. The LST was negative in cattle vaccinated with B abortus strain 19 (nonshedding), but the three serotests had many false-positive reactions. The CF test had the least false-positive reaction, followed by the RIV test, and the STT was the least specific. Well before the three serotests became positive, the LST was positive in samples from some cattle during the incubation period of the infection. There was little or no correlation between cell-mediated immune responses (as measured by LST) and serum antibody responses (as measured by STT, RIV test, and CF test) in vaccinated but culture-negative cattle and in some nonvaccinated cattle during the incubation period.

Agglutination Tests↗

PubMed1975

The indirect fluorescent antibody test for the detection of circulating antibodies in bovine tuberculosis.

Indirect fluorescent antibody (IFA) tests were carried out on a total of 545 individual serums from beef cattle just before tuberculin testing, using specific FITC-anti-bovine IgG and IgM conjugates. Phenol-killed M. tuberculosis (H37Rv strain) or field strains of M. bovis and M. avium were used as antigenic substrates. All cattle were examined at abattoirs for the presence of tuberculous lesions. A statistically significant difference (p less than 0.001) was found between the number of cattle with serums containing IgM and those with IgG antibody to M. bovis. The majority of cross-reactions that occurred with M. avium was due to IgM antibody. The IFA test using M. bovis and both antiglobulin conjugates detected 77% of cattle with visible lesions of tuberculosis, while the single intradermal caudal fold tuberculin test detected 83%. The IFA test detected 25 of 31 cattle with lesions that failed to react in the tuberculin test. The tuberculin test gave apparently false positive reactions in 6.2% and the IFA test gave false positive reactions in 21.2% of all cattle. The IFA test is of potential use as a further aid in the detection of tuberculous cattle that fail to react to tuberculin. It offers no advantage over the tuberculin test for the detection of all forms of the disease because it fails to detect a significant proportion of tuberculous cattle and produces an unacceptably high number of false positive results.

Animals↗

PubMed1976

False positive serology in cerebrospinal fluid associated with a spinal cord tumor.

Biologic false positive serology in cerebrospinal fluid has been reported as exceedingly rare. In a patient with a spinal cord tumor and elevated cerebrospinal fluid protein, the cerebrospinal fluid was reactive to VDRL and fluorescent treponemal antibody absorption (fta-abs) tests, but became nonreactive with removal of the tumor. This biologic false positive reaction may be related to the elevated cerebrospinal fluid protein, as similar false positive reactions have occurred in blood with abnormal or elevated proteins. Cerebrospinal fluid reactive to the VDRL and FTA-ABS tests does not always indicate neurosyphilis.

Cerebrospinal Fluid Proteins↗

PubMed1979

The frequency and identification of false positive conversion reactions.

The frequency with which conversion reaction diagnoses are inappropriately applied to persons with physical diseases was estimated in a sample of medical hospital patients diagnosed hysteric. This was accomplished by ratings based on file information available at the time of diagnosis and at a 10-year follow"up, and a count of patients whose "conversion" symptoms were later diagnosed as physical illnesses. The estimated false positive rate was 25%. The symptoms most characteristic of the false positives were degenerative diseases and structural failures affecting the spinal cord, peripheral nerves, bones, muscles, and connective tissues. An effort to identify psychological parameters capable of separating true conversion reactions from false positives with a variety of behavioral symptoms and Minnesota Multiphasic Personality Inventory scores was not productive.

Conversion Disorder↗

PubMed1976

Late syphilis. Otologic symptoms and results of the FTA-ABS test.

The clinician occasionally encounters a patient whose cochleovestibular symptoms are thought to be due to late syphilis mainly on the basis of a reactive FTA-ABS test. I describe 21 such patients, 11 of whom had either a spurious- or a false-positive reaction. The following suggestions may avoid an inaccurate diagnosis of late syphilis in such patients: (1) repeat all reactive serological tests for syphilis (STS); (2) rule out false-positive reactions; (3) request the degree of fluorescence (1+ to 4+) on all reactive FTA-ABS tests; (4) obtain a Treponema pallidum immobilization (TPI) test on all patients with repeatedly reactive (1+) FTA-ABS tests--a nonreactive TPI test rules out the diagnosis of syphilis; (5) if a TPI test cannot be performed, a repeatedly reactive (1+) FTA-ABS test in the absence of a reactive nontreponemal STS probably represents a false-positive reaction; (6) clinical judgment is the final determinant of whether a patient has or should be treated for late syphilis.

Adult↗

PubMed1976

Laboratoire d'Hygi'ene de la Facult'e de M'edecine de Lyon Universit'e Claude-Bernard, Domaine Rockefeller, 8, avenue Rockefeller, 69373 Lyon Cedex 2 France.

The objective of this study was to investigate the false-positive reactions in the Kline, FTA200 and FTA-ABS tests in acute disseminated lupus erythematosus, polyarthritis and controls. Though the false-positive Kline tests are frequent in autoimmune diseases, false-positive FTA200 when made on non lyophilised treponema are uncommon. On the other hand, when lyophilised treponema are used as substrate for the immunofluorescence, false-positive FTA200 and FTA-ABS are more common in the patients with autoimmune diseases than in controls. The false-positives had two patterns of fluorescence "beaded" or "homogeneous". The present investigation suggests that the false-positive reactions of the beaded type are due to the presence of anti-DNA antibodies in the sera.

Antibodies, Antinuclear↗

PubMed1976

Heterotypic antibodies in Liberian sera causing anomalous reactions when using a commercial haemagglutination test for hepatitis-B surface antigen.

Agglutinins reacting with normal and tanned sheep erythrocytes were the probable cause of false positive reactions given by 51 of 214 Liberian sera when using a commercial passive-haemagglutination test for hepatitis-B surface antigen. Absorption showed these agglutinins to be identical to those described earlier in Nigerian sera. Rheumatoid factor and anti-sheep-serum antibodies although present in 12 and five per cent respectively of all sera were not responsible for any false positive reactions. The practical conclusion is that such tests, based on sheep erythrocytes are unsuitable for screening this population.

Antibodies, Heterophile↗

PubMed1979

Discrimination of Antibodies to Hepatitis B surface antigen from antibodies to inherited serum protein variants in immune sera of human and animal origin.

Antisera to hepatitis B surface (HBs) antigen, both of human and rabbit origin, have been examined. The anti-HBs serum derived from a multiply transfused patient did, in addition, contain antibodies directed against the inherited beta-lipoprotein antigen Ag(x), whereas one of the rabbit immune sera also contained antibody to the inherited Lp(a) antigen. Thus, in human, as well as in animal anti-HBs sera, antibodies to inherited normal serum antigens may cause false positive reactions. This problem may be overcome by absorption procedures if appropriate control systems are available. False positive reactions caused by the Ag(x) antigen may also be avoided by use of agarose as supporting medium for the test, as Ag(x) precipitin lines do not appear in this medium. An undialysable high molecular weight component may be obtained from Oxoid "Ionagar" by washing. When this is added to agarose the Ag(x) antigen reaction appears also in this medium.

Absorption↗

PubMed1978

HBsAg immune complex glomerulonephritis.

Out of 97 patients with various forms of glomerulonephritis 10 were found to be HBsAg seropositive. None of these showed HBsAg immunodeposits within the kidney. Direct immunofluorescent kidney staining for HBsAg was observed in 4 out of 87 HBsAg seronegative patients. The HBsAg staining in kidneys was a false positive reaction due to binding of the Fc portion of the fluoresceinated IgG molecules to the IgM RF tissue deposits. The false positive reaction for HBsAg is not revealed by the usual specificity controls for fluorescence staining. The role of HBsAg in glomerulonephritis remains unproven.

Antigen-Antibody Complex↗

PubMed1977

[The phenoloxidase activity in the presence of H2O2, EDTA, and copper (author's transl)].

Investigations performed with cryostat sections of the gut, spleen and lung of the rat have shown, that the substrate of PER H2O2 inhibits the PO activity in dependence of the concentration, and that obvious the PO substrate DOPA is no suitable H2-donator for the PER reaction. Therefore a false positive reaction by the PO proof is not to be expected. Copper sulfat does not influence the PO reaction, but it accelerates melanin formation, which causes an unspecific colouring of the tissue.

Animals↗

PubMed1979

Analysis of the non-immunological activity of allergen extracts in cutaneous tests.

The technique proposed by the National Institute for Biological Standards and Control, London (NIBSC, 1977) for the control of allergenic extracts for non-immunological activity in skin tests has proved to be both sensitive and useful. We have observed 'false positive' results to substances such as merthiolate or glycerine and also to lyophilised preparations with sugar, notably glucose, as the carrier substance. Other factors studied in 'false positive' reactions to a given extract were pH, osmotic pressure and the presence of traces of endotoxins or histamine. Individually none of these provided satisfactory explanations for the false positive reactions and the use of antagonists or inhibitors of the release of chemical mediators only confirmed the complexity of the non-immunological reaction and the participation of factors other than histamine.

Allergens↗

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↗

PubMed1978

Complement fixation antibody test for human nocardiosis.

Complement-fixing antibody was detected in 13 of 16 patients with histological and/or culture evidence of infection with Nocardia species. The antigen used was a filtrate of soluble substances secreted into liquid growth medium by cultures of N. asteroides. Apparent false positives reactions were found in three of three patients with leprosy and two of five patients with tuberculosis--results similar to some previously reported methods. N. asteroides and mycobacteria share antigens. Only the false positives with tuberculosis are considered a diagnostic problem. No reactions were obtained with sera from 26 patients with other infections and 41 unifected individuals. Whereas previous nocardia serodiagnostic methods have a sensitivity of approximately 50%, our overall sensitivity (81%) compares favorably and included 9 of 11 positive tests in immunocompromised nocardiosis patients (a source of false negative reactions with previous methods).

Adult↗

PubMed1979

False-positive test results for syphilis in relatives of a patient with systemic lupus erythematosus.

In a family of nine members, two had systemic lupus erythematosus and seven positive serological test results for syphilis. None of the affected subjects had a history or physical signs of syphilis, but two had positive results to the Treponema pallidum immobilisation test. The explanation for these findings is not known, but possibily they were all false-positive reactions.

Adolescent↗