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PubMed1992

Prevalence of hepatitis B and C and HIV antibodies in children in a Romanian orphanage.

Two hundred and fifteen children in an orphanage in Romania were examined for serum markers of present or past hepatitis B and C virus and HIV infection. In total, 183 children (85.1%) had at least one marker (HBsAg, anti-HBs or anti-HBc) of hepatitis B virus infection. An HBsAg carrier state was diagnosed in 38 (20.8%) of the infected children. Among the carriers 24.3% were HBeAg carriers, 51.4% had anti-HBe and 24.3% had neither HBe antigen nor antibody. Nine children (4.2%) had antibodies to hepatitis C virus. All sera were negative in tests for HIV antibodies. False-positive reactions represented a considerable problem with these sera. Six percent of the sera gave false-positive reactions in indirect ELISA tests for hepatitis C and HIV. Sera giving false-positive reactions had rather high serum IgG levels. The results of this study indicate that these children have been heavily exposed to hepatitis B virus and to a certain degree to hepatitis C virus, while there were no cases of HIV infection in this orphanage.

Child↗
PubMedDate not supplied

Evaluation of three enzyme immunoassays for HIV-1 antigen detection.

Three enzyme immunoassay (EIA) methods for the detection of human immunodeficiency virus (HIV-1) were evaluated. Serum or plasma samples from 22 individuals seropositive for HIV-1 antibodies were tested with the Abbott, Coulter, and DuPont kits for presence of HIV-1 p24 antigen. Another 12 samples were tested with two kits only. Discordant results were obtained with 9 of 34 (26%) HIV-1-antibody-positive patient samples tested. Most of these discrepancies were found in samples containing less than 30 pg/ml of HIV-1 p24 core antigen. A sampling of sera from normal blood donors and patients with infectious or autoimmune diseases revealed a low level of false positive reactions, especially with sera containing antinuclear antibodies or rheumatoid factor. Noteworthy is the frequency of false positive reactions seen with the DuPont EIA for HIV-1 p24 antigen. 18/111 sera (16.2%) containing auto-antibodies tested positively with the DuPont HIV-1 p24 antigen EIA. The nonspecific nature of the test reactivity for 9/10 of these samples was confirmed using an HIV-1 p24 antigen inhibition assay. These findings are discussed in light of the need for HIV-1 antigen detection in the clinical laboratory and of other methods for HIV-1 detection: the polymerase chain reaction and measurements of reverse transcriptase activity.

Evaluation Studies as Topic↗
PubMed1994

A more reliable PCR for detection of Mycobacterium tuberculosis in clinical samples.

Diagnostic techniques based on PCR have two major problems: false-positive reactions due to contamination with DNA fragments from previous PCRs (amplicons) and false-negative reactions caused by inhibitors that interfere with the PCR. We have improved our previously reported PCR based on the amplification of a fragment of the Mycobacterium tuberculosis complex-specific insertion element IS6110 with respect to both problems. False-positive reactions caused by amplicon contamination were prevented by the use of uracil-N-glycosylase and dUTP instead of dTTP. We selected a new set of primers outside the region spanned by the formerly used primers to avoid false-positive reactions caused by dTTP-containing amplicons still present in the laboratory. With this new primer set, 16 copies of the IS6110 insertion element, the equivalent of two bacteria, could be amplified 10(10) times in 40 cycles, resulting in a mean efficiency of 77% per cycle. To detect the presence of inhibitors of the Taq polymerase, which may cause false-negative reactions, part of each sample was spiked with M. tuberculosis DNA. The DNA purification method using guanidinium thiocyanate and diatoms effectively removed most or all inhibitors of the PCR. However, this was not suitable for blood samples, for which we developed a proteinase K treatment followed by phenol-chloroform extraction. This method permitted detection of 20 M. tuberculosis bacteria per ml of whole blood. Various laboratory procedures were introduced to reduce failure or inhibition of PCR and avoid DNA cross contamination. We have tested 218 different clinical specimens obtained from patients suspected of having tuberculosis. The samples included sputum (n=145), tissue biopsy samples (n=25), cerebrospinal fluid (n=15), blood (n=14), pleural fluid (n=9), feces, (n=7), fluid from fistulae (n=2), and pus from a wound (n=1). The results obtained by PCR were consistent with those obtained with culture, which is the "gold standard." We demonstrate that PCR is a useful technique for the rapid diagnosis of tuberculosis at various sites.

Bacteriological Techniques↗
PubMed2004

[False positive and false negative reaction results based on an amplification of nucleic acids in infection diagnoses. Reasons and implications].

The paper discusses the most frequent causes of false positive and false negative results of reactions based on amplification of nucleic acids. All stages of the method are described beginning with sample collection up to the finishing of visualization of amplification product. The main aim objective of the publication is to draw doctors' attention to the necessity to interpret the result with criticism. We attempted also to demonstrate how to avoid false results.

Animals↗
PubMedDate not supplied

Reevaluation of diagnostic histoplasma serologies.

There are few quantitative guidelines for the interpretation of serologic tests for histoplasmosis. Furthermore, guidelines that have been proposed are not accepted generally. This report reviews experiences with complement fixation and latex agglutination tests performed in a large acute-care hospital in an endemic area, and depicts the relationship between the proportion of false-positive reactions and the titer at which the serologic tests were reactive. We noted a considerable number of false-positive reactions for these widely-used tests. Use of a battery of standard tests for histoplasmosis resulted in a 90% decrease in false-positive reactions. Reliance upon multiple positive results in such a battery of tests would result in failure to detect 50% of cases of disseminated histoplasmosis, but would eliminate most false positives.

Complement Fixation Tests↗
PubMed1998

False-positive tests for syphilis associated with human immunodeficiency virus and hepatitis B virus infection among intravenous drug abusers. Valencian Study Group on HIV Epidemiology.

The role of HIV, hepatitis C virus, and hepatitis B virus infections in the production of biological false-positive reactions for syphilis was evaluated in two large samples of intravenous drug abusers and homosexual men attending AIDS prevention centers in Spain. A significantly increased odds ratio (OR) for false-positive tests for syphilis [OR 2.23, 95% confidence intervals (CI) 1.76-2.83] was observed for HIV-seropositive intravenous drug abusers; biological false-positive reactions were also more frequent (OR 1.73, 95% CI 1.30-2.31) among intravenous drug abusers who were hepatitis B virus seropositive but not among those who were hepatitis C virus seropositive (OR 0.90; 95% CI 0.48-1.69). Among homosexuals, the association between HIV and biological false-positive reactions was restricted to subjects who were also intravenous drug abusers, indicating the crucial role of intravenous drug abuse. Only 20.5% of intravenous drug abusers with a previous biological false-positive reaction yielded a false-positive result in their subsequent visit.

Antibodies, Bacterial↗
PubMedDate not supplied

False positive serological reactions in bovine brucellosis: evidence of the role of Yersinia enterocolitica serotype O:9 in a field trial.

To investigate the epidemiology of false positive serological reactions (FPSR) in bovine brucellosis, 1259 bovines from 20 herds were sampled on three successive occasions during the winter of 1993-1994 in an area where the herd prevalence rate of FPSR was high. Serum samples were examined by classical brucellosis serological tests (Rose Bengal and complement fixation) and faeces were cultured for the presence of Yersinia enterocolitica O:9. Thirty-nine bovines expressed at least one positive serological reaction during the study. In the herds with FPSR during the 1993-1994 annual brucellosis surveillance campaign, the specificity of the brucellosis serological tests varied significantly from December to March (97.0% to 99.1%). Y enterocolitica O:9 was isolated from 42 bovines but only three of them showed a positive serological response during the study. Y enterocolitica O:9 isolation rates also decreased with time. Young animals and animals having demonstrated FPSR in the past had a greater risk of having a FPSR. Older animals, which rarely showed FPSR, could form a reservoir for Y enterocolitica O:9. While isolation of Y enterocolitica O:9 was not linked to presence of FPSR and conversely, the FPSR phenomenon should be considered, either at the herd level or at the individual level. This work reinforces the link, at least partial, between FPSR and infection by Y enterocolitica O:9.

Animals↗
PubMed2002

Cutaneous adverse reactions to clindamycin: results of skin tests and oral exposure.

BACKGROUND: Clindamycin is an antibiotic used in anaerobic and severe complicated infections. It is often selected for patients with a history of allergy to other antibiotics. OBJECTIVES: To study the occurrence of clindamycin hypersensitivity and to determine whether skin tests are useful in cases of suspected clindamycin allergy. METHODS: Six patients with an exanthematous rash and a history strongly suggestive of clindamycin hypersensitivity were studied with skin tests and oral exposure. Cases of suspected adverse drug reactions to clindamycin reported to the National Register of Adverse Effects of Drugs (NRAED) in Finland during 1973-2000 were analysed. RESULTS: In the skin tests true-positive patch test reactions were seen in four of six patients, while 22 healthy control patients were negative. One false-positive and one false-negative patch test reaction were seen. During 1973-2000, 29 suspected cases of skin and/or mucosal membranes affected by clindamycin were reported to the NRAED. CONCLUSIONS: Clindamycin hypersensitivity is not common. Delayed-type allergic reactions occur and patch tests are useful in those cases. Oral exposure is the method of choice if possible, as false-negative and false-positive reactions may occur.

Administration, Oral↗
PubMed2002

[Comparison of eight screening tests for ant-HCV antibody].

We compared eight HCV screening tests for detection of anti-HCV antibody; Ortho Quick Chaser HCV Ab (QC), Ortho HCV Ab ELISA III (ELISA), Ortho HVC Ab PA test III (PA), Lumipulse II Ortho HCV (LUMI), IMx HCV.DAINAPACKII (IMx), ARCHITECT HCV (ARCH), Immucheck.F-HCV C50 Ab (Immu), RANREAM HCV Ab Ex II (RAN). Sera from six hundred patients were examined by these eight screening tests. The positive rates of the eight screening tests were from 9.0% to 13.2%. Forty-five sera showed discrepant results between the eight screening tests, and about half of them showed weak positive reaction and/or false positive. Twenty-five of the forty-five sera were negative for ant-HCV antibody in the CHIRON RIBA III confirmatory test, and forty-four of them were negative for HCV-RNA in the PCR method. The agreement rates between the two reagents were from 95.5% to 99.2%, but were not always high between the two reagents that used similar antigen. The specificities and sensitivities evaluated by using the RIBA III confirmatory test were excellent in ELISA, LUMI, IMx, ARCH and Immu. Three BBI seroconversion panels were used to compare the positive readings in the initial stage of HCV infection by eight screening tests. ELISA and ARCH showed the earliest positive readings, and then IMx, LUMI = RAN, PA, QC and Immu in this order. These findings indicate that ELISA and ARCH were the most excellent in the sensitivity, specificity and early diagnosis of HCV infection. However, we must pay attention to the weak positive reaction in the screening tests, because there is a possibility of "false positive".

False Positive Reactions↗
PubMedDate not supplied

The Brucellin skin test as a tool to discriminate false positive serological reactions in bovine brucellosis.

Three experiments were performed in order to assess the diagnostic value of the Brucellin allergic skin test (AST) in a brucellosis false positive serological reactions (FPSR) context. First, 1259 cattle from 20 Brucella-free herds in a FPSR area were tested twice with AST to estimate its specificity. Secondly, AST and serological tests (complement fixation test [CFT], tube agglutination test, dithiothreitol-microagglutination test and ELISA) sensitivities were evaluated on 111 cattle positive to the Rose Bengal test (RBT) belonging to 15 Brucella-infected herds. Thirdly, AST was used in a field trial to discriminate FPSR from true brucellosis reactions. AST specificity in non-vaccinated cattle was very high (99.83%; confidence interval 95% [CI95%]: 99.67-99.96%). Skin thickening 72 h post-injection was significantly higher on vaccinated cattle (1.42 vs 0.15 mm). In this sub-population, AST specificity decreased significantly to 78% (CI95%: 68-87%). Individual sensitivity of AST relative to Rose Bengal test was 64% (CI95%: 54-72%), while all infected herds were AST positive (n = 15). When associated with CFT, it detected 95% (CI95%: 90-98%) of the infected cattle. These results were consistent with the field trial. In a FPSR context, AST was more specific than RBT or CFT. Therefore, this test could be used at herd level as a confirmation test, on cattle non vaccinated against brucellosis.

Animals↗
PubMed1976

Effects of hemoglobin F levels, KCN, and storage on the isopropanol precipitation test for unstable hemoglobins.

Although the isopropanol precipitation test is a commonly used and sensitive test for detecting unstable hemoglobins, false-positive reactions are frequently observed. In this study, the storage temperature of the test samples, type of stored sample amount of fetal hemoglobin (Hb F) in the sample, and presence of potassium cyanide (KCN) in the hemolysate preparation all affected the accuracy of the test. The addition of 2% KCN to samples before testing eliminated or greatly reduced false-positive reactions. Hb F levels greater than 4% caused false-positive results. When specimens with Hb F levels less than 4% were stored at 4C and as whole blood, they showed no false-positive reaction for as long as two weeks. However, duplicate specimens stored as whole blood but unrefrigerated and those stored as hemolysates showed false-positive reactions after three days.

1-Propanol↗
PubMed1983

Comparison of three commercial cryptococcal latex kits for detection of cryptococcal antigen.

Three commercial latex kits, IBL, MYCO-Immune, and IMMY, for the detection of cryptococcal antigen were compared in regard to sensitivity, specificity, and height of antigen titers. A total of 218 cerebrospinal fluid and 79 serum specimens from 239 patients were included. Twenty-two patients had culture-proven disseminated cryptococcosis. Both the IBL and MYCO-Immune kits had sensitivities of 100%, and the IMMY kit had sensitivities of 82.6 and 45.4% in CSF and serum specimens, respectively. There was one false-positive reaction in serum with the MYCO-Immune kit and one false-negative reaction on screen only with all three kits. Rheumatoid factor-containing sera were used to check the agglutination titers between matching anti-cryptococcal globulin reagents and normal globulin reagents. The finding that agglutination titer with anti-cryptococcal globulin reagents was fourfold higher than with normal globulin reagents in the MYCO-Immune kit is considered to be a cause for a false-positive reaction in serum.

Antigens, Bacterial↗
PubMed1992

Specificity of affinity-purified Trichinella spiralis antigens.

An affinity-purified fraction (APF) was obtained by passing crude somatic antigens of Trichinella spiralis muscle larvae through an Affi-Gel 10 column coupled with anti-Trichuris suis IgG. The fraction contained seven antigens with molecular weights ranging from 28 to 55 kDa. When tested with antiserum against other common nematodes of pigs from China, the APF was found to be markedly more specific than S3 antigens (prepared by a combination of cell fractionation and differential centrifugation according to Despommier and Lacetti, 1981) and fractions produced by Sephacryl S-200 gel filtration (F1 to F12). When the APF was used in an indirect IgG-enzyme-linked immunosorbent assay (IgG-ELISA) to screen serum samples from 2000 pigs imported from China, a positive rate of 7.5% was obtained. Similar screenings using the crude somatic antigens F1 and S3 gave a large number of cross-reactions and false positive reactions. Positive rates of 48%, 39% and 59.5% respectively were obtained for the three antigens.

Animals↗