Evitar o efeito da vacinação BCG na detecção de infecção por Mycobacterium tuberculosis com um teste sanguíneo (original) (raw)
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European Respiratory Journal, 2006
Bacille Calmette-Guérin (BCG) vaccination can confound tuberculin skin test (TST) reactions in the diagnosis of latent tuberculosis infection (LTBI). The TST was compared with a Mycobacterium tuberculosis (MTB)-specific enzyme-linked immunospot (ELISPOT) assay during an outbreak of MTB infection at a police academy in Germany. Participants were grouped according to their risk of LTBI in close (n536) or occasional (n5333) contacts to the index case. For the TST, the positive response rate was 53% (19 out of 36) among close and 16% (52 out of 333) among occasional contacts. In total, 56 TST-positive contacts (56 out of 71578.9%) and 27 TST-negative controls (27 out of 29859.1%) underwent ELISPOT testing. The odds ratio (OR) of a positive test result across the two groups was 29.2 (95% confidence interval (CI) 3.5-245.0) for the ELISPOT and 19.7 (95% CI 2.0-190.2) for the TST with a 5 mm cutoff. Of 369 contacts, 158 (42.8%) had previously received BCG vaccination. The overall agreement between the TST and the ELISPOT was low, and positive TST reactions were confounded by BCG vaccination (OR 4.8 (95% CI 1.3-18.0)). In contrast, use of a 10-mm induration cutoff for the TST among occasional contacts showed strong agreement between TST and ELISPOT in nonvaccinated persons. In bacille Calmette-Guérin-vaccinated individuals, the Mycobacterium tuberculosis-specific enzyme-linked immunospot assay is a better indicator for the risk of latent tuberculosis infection than the tuberculin skin test.
Respiratory Research, 2006
Background: BCG-vaccination can confound tuberculin skin test (TST) reactions in the diagnosis of latent tuberculosis infection. Methods: We compared the TST with a Mycobacterium tuberculosis specific whole blood interferon-gamma assay (QuantiFERON ®-TB-Gold In Tube; QFT-G) during ongoing investigations among close contacts of sputum smear positive source cases in Hamburg, Germany. Results: During a 6-month period, 309 contacts (mean age 28.5 ± 10.5 years) from a total of 15 source cases underwent both TST and QFT-G testing. Of those, 157 (50.8%) had received BCG vaccination and 84 (27.2%) had migrated to Germany from a total of 25 different high prevalence countries (i.e. >20 cases/100,000). For the TST, the positive response rate was 44.3% (137/309), whilst only 31 (10%) showed a positive QFT-G result. The overall agreement between the TST and the QFT-G was low (κ = 0.2, with 95% CI 0.14.-0.23), and positive TST reactions were closely associated with prior BCG vaccination (OR 24.7; 95% CI 11.7-52.5). In contrast, there was good agreement between TST and QFT-G in non-vaccinated persons (κ = 0.58, with 95% CI 0.4-0.68), increasing to 0.68 (95% CI 0.46-0.81), if a 10-mm cut off for the TST was used instead of the standard 5 mm recommended in Germany. Conclusion: The QFT-G assay was unaffected by BCG vaccination status, unlike the TST. In close contacts who were BCG-vaccinated, the QFT-G assay appeared to be a more specific indicator of latent tuberculosis infection than the TST, and similarly sensitive in unvaccinated contacts. In BCGvaccinated close contacts, measurement of IFN-gamma responses of lymphocytes stimulated with M. tuberculosis-specific antigen should be recommended as a basis for the decision on whether to perform subsequent chest X-ray examinations or to start treatment for latent tuberculosis infection.
Comparison of Tuberculin Skin Test and New Specific Blood Test in Tuberculosis Contacts
American Journal of Respiratory and Critical Care Medicine, 2004
The Tuberculin skin test, used to detect latent Mycobacterium tuberculosis infection, has many drawbacks and a new diagnostic test for latent tuberculosis (QuantiFERON ? -TB) has recently been introduced. This test measures the production of interferon-? in whole blood upon stimulation with Purified Protein Derivative. The QuantiFERON ? -TB test addresses the operational problems with the tuberculin skin test, but as the test is based on Purified Protein
Tuberculin reactivity in adult BCG-vaccinated subjects: a cross-sectional study
I N T R O D U C T I O N : Interpretation of the tuberculin skin test (TST) may be complicated by prior bacille Calmette-Guérin (BCG) vaccination. The skin reaction to the vaccination interferes with the management of individuals who may be infected with Mycobacterium tuberculosis. O B J E C T I V E : To discriminate between TST reactions due to infection and those due to vaccination in subjects with unknown BCG status. M E T H O D S : Among 60 200 subjects tested with 5TU PPD for screening purposes, 4987 contacts of infectious TB cases (Group A), 4962 BCG-vaccinated subjects (Group B) and 5000 subjects from the general population (Group C) were sampled. The frequencies of TST cut-off diameters were calculated for the three groups using a logistic regression model. The frequency of pos-itive subjects in each group and the sensitivity, specificity and predictive values were also computed by means of these cut-offs. R E S U L T S : The risk of being a contact versus BCGvaccinated increases 2.43-fold with every mm of TST diameter. The 11 mm cut-off point seems to be the best discriminating value. C O N C L U S I O N S : Using the traditional 10 mm cut-off, we can consider all vaccinated subjects with a positive TST to be infected. The TST remains a valuable tool for the evaluation of household contacts and suspected cases of tuberculosis in BCG-vaccinated subjects and in populations with high vaccination coverage. K E Y W O R D S : tuberculin test; BCG vaccine; TST
Clinical Diagnostic Laboratory Immunology, 2001
The tuberculin skin test (TST) is used for the identification of latent tuberculosis (TB) infection (LTBI) but lacks specificity in Mycobacterium bovis BCG-vaccinated individuals, who constitute an increasing proportion of TB patients and their contacts from regions where TB is endemic. In previous studies, T-cell responses to ESAT-6 and CFP-10, M. tuberculosis -specific antigens that are absent from BCG, were sensitive and specific for detection of active TB. We studied 44 close contacts of a patient with smear-positive pulmonary TB and compared the standard screening procedure for LTBI by TST or chest radiographs with T-cell responses to M. tuberculosis -specific and nonspecific antigens. Peripheral blood mononuclear cells were cocultured with ESAT-6, CFP-10, TB10.4 (each as recombinant antigen and as a mixture of overlapping synthetic peptides), M. tuberculosis sonicate, purified protein derivative (PPD), and short-term culture filtrate, using gamma interferon production as the r...
2020
Introduction: The Mantoux tuberculin skin test (TST) for the diagnosis of latent tuberculosis infection (LTBI) has a variable performance and limited usefulness in Bacillus Calmette-Guérin (BCG)-vaccinated populations. Objective: The objective of the study was to evaluate the performance of the TST for the diagnosis of LTBI in household contacts of patients with active pulmonary tuberculosis (PTB). Materials and methods: The TST was administered to 113 cases with PTB and 194 household contacts. The gold standard was the bacteriological confirmation in patients. The household contacts were classified as true positives according to the selected cutoff point. Those with purified protein derivative reactivity less than the cutoff point but different from zero were classified as false positives. The area under the curve was measured and the best cutoff point was determined. Sensitivity, specificity, positive and negative predictive values (PV), and positive and negative likelihood ratios (LR) were measured with 2 × 2 contingency tables. Results: The best cutoff point was at 10 mm of induration, with an area under the curve of 0.93, sensitivity 85%, specificity 88%, positive PV 94%, negative PV 71%, positive LR 6.9, and negative LR 0.17. There was no association between reactivity to TST and BCG vaccination, OR (95% confidence interval CI) 1.14 (0.65-2.10), p = 0.644. Conclusions: The TST showed a very good performance, as it lead to an important change from pre-test to post-test probability.
Clinical Microbiology and Infection, 2004
The relationship of age and previous BCG vaccination with tuberculin skin test (TST) reactivity was investigated to assess the interpretation of TST results in the adult population of Turkey, where there is a high prevalence of tuberculosis and a routine BCG vaccination programme. The influences of age and BCG vaccine status on booster reaction were also evaluated. TST was applied (5 tuberculin units of purified protein derivative intradermally) to two healthy adult groups, namely 98 medical students and 187 elderly people in a retirement home. The TST was considered positive if an induration ‡ 10 mm in diameter was produced. Subjects (41 elderly people and 39 students) with a reaction < 10 mm in diameter were retested 1 week later. There was no significant difference between the students (59.1%) and elderly subjects (58.8%) with respect to positive TST response. No influence of BCG scars on TST reactivity was observed in either group. The booster effect was seen more commonly in the elderly, but the presence of a BCG scar did not influence the booster effect in either group. It was concluded that a positive TST response and booster reaction in adults in high-prevalence countries may be caused by latent tuberculosis rather than previous vaccination.
The Lancet, 2003
Background The diagnosis of latent tuberculosis infection relies on the tuberculin skin test (TST), which has many drawbacks. However, to find out whether new tests are better than TST is difficult because of the lack of a gold standard test for latent infection. We developed and assessed a sensitive enzyme-linked immunospot (ELISPOT) assay to detect T cells specific for Mycobacterium tuberculosis antigens that are absent from Mycobacterium bovis BCG and most environmental mycobacteria. We postulated that if the ELISPOT is a more accurate test of latent infection than TST, it should correlate better with degree of exposure to M tuberculosis.