Immunoglobulin A (IgA) and IgG immune responses against P-90 antigen for diagnosis of pulmonary tuberculosis and screening for Mycobacterium tuberculosis infection

The purpose of the present study was to evaluate the usefulness of detection of serum immunoglobulin A (IgA) and IgG antibodies directed against the mycobacterial P-90 antigen for the diagnosis of active pulmonary tuberculosis (PTB) among symptomatic individuals and for the detection of Mycobacterium tuberculosis infections among close contacts of PTB patients. Two commercially available enzyme immunoassay (EIA) kits (IgA EIA-TB [EIA-IgA] and IgG EIA-TB [EIA-IgG]; Kreatech Diagnostics) were evaluated in a blinded fashion by using stored serum samples from 268 individuals, including 69 patients with PTB, 41 patients with diseases other than tuberculosis (TB), 12 subjects with healed PTB, 39 close contacts of PTB patients, and 107 healthy volunteers. For the EIA-IgA, the sensitivity was 74% and the specificity was 68% when a cutoff determined by a receiver operator characteristic curve was used. For the EIA-IgG, the sensitivity was 69% and the specificity was 64%. The EIA-IgA was positive for 54% of healthy close contacts of PTB patients but only 8% of healthy controls without contact with a PTB patient or a prior personal history of TB (P < 0.001). The relatively low sensitivities and specificities of these serologic tests make them poor tools for the diagnosis of PTB among patients with suspected PTB. However, the relatively high prevalence of positive EIA-IgA results among healthy close contacts of PTB patients warrants further evaluation of this test with close contacts and other populations at risk for recent M. tuberculosis exposure and development of disease.     

Serologic diagnosis of tuberculosis using a simple commercial multiantigen assay

SETTING: Seven primary health clinics and a pulmonary disease specialty clinic in Rio de Janeiro City, Brazil. OBJECTIVE: To evaluate a commercial immunochromatographic test kit (ICT Tuberculosis; AMRAD-ICT; Sidney, Australia) employing five recombinant Mycobacterium tuberculosis proteins for the detection of pulmonary tuberculosis (TB). DESIGN: Serology test results were compared with duplicate sputum microscopy and culture in 277 patients with symptomatic pulmonary disease (243 with pulmonary TB and 34 with nontuberculous disease). An additional 110 healthy control subjects were also tested. RESULTS: The serology test was simple and rapid to perform and detected 64.2% of smear-positive and 46.3% of smear-negative TB patients overall. HIV co-infection was present in 15.3% of TB patients, and serology was much less sensitive (overall 27.6%) in this small group, as was microscopy (13.8%). Specificity of the serology test was 100% in healthy control subjects and 85.2% in the small number of control patients with pulmonary disease, including those with prior TB. Combined with microscopy, serology detected 72.8% of TB patients. CONCLUSION: Depending on the population studied, multiantigen serologic tests for TB may be as sensitive as microscopy, but detect a different and overlapping subset of patients. The use of multiple antigens in this kit increased test sensitivity without significant loss of specificity. Bacille Calmette-Guérin vaccination and tuberculin sensitivity did not affect serology results. Estimating specificity in clinical use will require testing a much larger cohort of symptomatic patients with nontuberculous disease. The TB diagnostic performance of this group of antigens in HIV co-infected individuals was poor.     

Clinical evaluation of the microscopic observation drug susceptibility assay for detection of Mycobacterium tuberculosis resistance to isoniazid or rifampin

This prospective study evaluated the performance of the microscopic observation drug susceptibility (MODS) assay for the direct detection of Mycobacterium tuberculosis drug resistance. MODS assay sensitivity, specificity, and positive and negative predictive values were 96.7% (95% confidence interval [95% CI], 92.1 to 98.8%), 78.4% (95% CI, 73.5 to 80.6%), 82.4% (95% CI, 78.4 to 84.2%), and 95.8% (95% CI, 89.9 to 98.5%), respectively, for isoniazid resistance and 96.0% (95% CI, 90.3 to 98.6%), 82.9% (95% CI, 78.8 to 84.7%), 80.0% (95% CI, 75.2 to 82.1%), and 96.7% (95% CI, 91.9 to 98.8%), respectively, for rifampin resistance. For both rifampin and isoniazid testing, the likelihood ratio for a negative test was < or =0.05, indicating that the MODS assay may be useful for ruling out drug resistance.     

Tuberculosis teaching in Brazilian medical schools.

To achieve tuberculosis (TB) control, National Tuberculosis Programme guidelines should be implemented effectively. In a survey conducted in 2005-2006, 33 Brazilian medical school coordinators answered a questionnaire about TB education. The median time dedicated to TB was 27 h (4-119 h), spread over several disciplines, mainly biological and clinical. This included 12 h (0-88 h) of practical activities, mainly in university hospitals (53%). The recommendation to offer human immunodeficiency virus testing for TB patients was taught in only 54% of the schools. TB education in Brazil is fragmented and restricted to a biological approach, while field activities are insufficient and carried out in inadequate settings. Important changes to the TB curriculum are necessary.     

A multicenter evaluation of tuberculin skin test positivity and conversion among health care workers in Brazilian hospitals.

SETTING: Four general Brazilian hospitals. OBJECTIVE: To assess the occupational risk of Mycobacterium tuberculosis (TB) in participating hospitals. DESIGN: In phase one of this longitudinal study, a cross-sectional survey documented baseline tuberculin skin test (TST) positivity rates. In phase two, TST conversion rates were evaluated in participants with an initial negative two-step TST. TST conversion data were analyzed to determine risk factors for TB infection using an increase of > or = 10 mm compared to baseline TST. RESULTS: The initial TST positivity rate was 63.1%; the follow-up TST conversion rate was 10.7 per 1000 person-months (p-m). Hospital of employment, recent bacille Calmette-Guerin (BCG) vaccination, nosocomial TB exposure, and employment as a nurse were independent risk factors for TST conversion. Hospitals without TB infection control measures had higher conversion rates than those with control measures (16.0 vs. 7.8/ 1000 p-m, P < 0.001). CONCLUSIONS: This study indicates an important occupational risk of infection in health care settings with a high TB incidence. Longitudinal TST studies are a valuable tool to assess the occupational risk of TB, even in BCG-vaccinated populations, and should be used to direct limited resources for infection control.