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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↗
PubMed1976

The value of the skin test and complement fixation test in the diagnosis of chronic pulmonary histoplasmosis.

Histoplasmin skin test results in patients with chronic pulmonary histoplasmosis from Missouri and Texas were compared to results in a previous study of U.S. Navy recruits. When consideration was given to geographic areas from which persons from each group were admitted to the study, it was found that the recruits were as likely to have a positive skin test as were those with the disease. In a similar manner, the Texas histoplasmosis patients were compared to groups of patients from that state with chronic obstructive pulmonary disease and with pulmonary tuberculosis. Again, no significant differences were found. It was concluded that the histoplasmin skin test is not of value in the diagnosis of chronic pulmonary histoplasmosis. Histoplasmosis complement fixation test data from the chronic pulmonary histoplasmosis group were compared to data from the chronic obstructive pulmonary disease and pulmonary tuberculosis groups. The usefulness of the complement fixation test in chronic pulmonary histoplasmosis is limited, as with any test, by false-positive and false-negative reactions. A decision theory method was used to define the limits of usefulness.

Chronic Disease↗
PubMed1976

A comparative study of passive haemagglutination methods for the detection of hepatitis B surface antigen in routine hospital practice.

Two passive haemagglutination methods for detecting HBsAg were compared. In general, the method using turkey erythrocytes was found preferable to the method employing sheep cells since it is more rapid and more sensitive, and less frequently gave rise to false positive reactions with sera from staff, blood donors, and patients not receiving haemodialysis. The turkey cell test gives rise to more false positive screen tests than the sheep cell test when monitoring renal dialysis patients since approximately 10% of the sera of these patients were found to contain turkey cell agglutinins, but this presents no particular difficulty if the recommended absorption procedures are used.

Animals↗
PubMed1976

Importance of the autocontrol crossmatch in human renal transplantation.

The killing of donor cells in the standard lymphocyte crossmatch is considered strong evidence for preformed antibodies in the recipients's serum. Moreover, it is generally accepted that presensitization has occurred if any of the stored sera kill the donor cells. In our hands, if either the current or the stored sera kill the donor cells, it precludes transplantation. In nine cases we discovered that the recipient's sera also killed the recipient's own lymphocytes, a positive autocontrol test, indicating that factors other than conventional preformed cytotoxic antibodies were responsible for the positive standard crossmatch. The nine patients who demonstrated a positive standard crossmatch and a positive autocontrol for those sera received cadaver allografts. None of the kidneys were rejected hyperacutely and all are functioning adequately. We conclude that the autocontrol crossmatch is an important adjunct for uncovering false positive reactions in the standard lymphocyte crossmatch test.

Adolescent↗
PubMedDate not supplied

Noneffect of oral urinary copper ascorbic acid on reduction glucose test.

References and texts in the fields of diabetes and clinical chemistry commonly report that ascorbic acid when given orally or parenterally gives a false-positive reaction to the copper reduction glucose test (Clinitest). This impression is based on a study in which ascorbic acid (250 mg./dl.) was added to urine in vitro, with a resultant positive-test reading in the absence of glucose. Ascorbic acid is a reducing agent, and theoretically it could interfere with the copper reduction method of glucose detection. In the current study 10 nondiabetic men were ingesting 4 and 6 gm. ascorbic acid per day. A total of 360 glucose detection tests with the copper reduction method were undertaken. In no instance was there a positive reaction to the glucose test.

Administration, Oral↗
PubMed1978

Evaluation of methods to detect antibodies against Aspergillus fumigatus.

Seventy-five sera, including sera from 23 patients with aspergillosis, 17 with tuberculosis, asthma or carcinoma, and 35 normal controls, were studied for antibody activity against Aspergillus fumigatus by agar gel double diffusion (DD), counterimmunoelectrophoresis (CIE), indirect hemagglutination (IHA) and indirect immunofluorescence (IF). Metabolic antigens produced from a selected strain of A. fumigatus were used for DD, CIE and IHA, while slide cultures of the same organism were used for IF. The results indicated that sera from the patients with aspergillosis had high IHA and IF titers, while only 91 and 87% were positive for CIE and DD methods, respectively. IHA was more sensitive than DD and CIE, and IF was equally sensitive but had false-positive reactions. CIE was simple and fast, but had false-negative and occasionally false-positive results.

Antibodies, Fungal↗
PubMed1976

Tonic pupil: a simple screening test.

The tonic pupil has a typical appearance and characteristic reactions to both light and the near reflex. Testing with Mecholyl (methacholine) is not possible since the drug is no longer manufactured. The reactions of a group of 25 patients with tonic pupil were studied using dilute pilocarpine, and compared with the pupil responses of a separate control group. We found that concentrations of 0.2% pilocarpine produced too many false-positive reactions in the control group and that 0.05% pilocarpine produced an insufficient response. The 0.1% concentration seemed suitable for ordinary clinical examinations and is recommended for pharmacologic confirmation of the diagnosis of tonic (Adie's) pupil.

Adie Syndrome↗
PubMed1977

Screening of HBs antigen and detection of corresponding antibodies on groupamatic equipment.

The widespread utilization of Groupamatic equipment for routine immunohaematological tests has increased the demand for serological procedures that can be performed with this machine. We describe the test method which was developed and with which the detection of HBs antigen has now been carried out routinely for 1 year. It is an automated haemagglutination inhibition reaction which is called GIPHA (Groupamatic inhibition of passive haemagglutination). The sensitivity corresponds to 2 CNTS units, the antigen weight for 1 unit being from 1 to 4 ng. The reproducibility is good; the percentage of false positive reactions is about 0.5% and that of technical problems 0.7%. The additional advantages of the machines are numerous, among which we have the possibility of 11 other simultaneous reactions. One of them is the detection of antibodies against HBs antigen, which is a passive haemagglutination test called PHAG (passive haemagglutination on Groupamatic).

Antibodies↗
PubMed1976

Screening for syphilis in an aged psychiatrically impaired population.

A serum Venereal Disease Research Laboratories (VDRL) test was carried out in 216 elderly patients with dementia or "functional" psychiatric illness, or both, as part of a community based screening program. The VDRL test was positive in 13 patients, 11 of whom (5.1 percent) had an actual past or present syphilitic infection as confirmed by the fluorescent treponemal antibody absorption test (FTA-Abs). In six patients (2.8 percent) syphilis was newly detected, and in another two patients previously detected syphilis had been inadequately treated. Only two (0.9 percent) biologic false positive reactors were detected. These results question the belief that aging per se is a common cause of the biologic false positive reaction; and indicate a relatively high incidence of past or present syphilitic infection in geriatric patients with psychiatric illness in the community who have been referred for crisis intervention.

Aged↗