Israel Medical Association Journal

Background: Determining the accuracy of interferon gamma-releasing assays (IGRAs) is difficult due to the lack of a gold standard test for diagnosing latent tuberculosis (LTB). 

Objectives: To analyze the guidelines used for interpreting IGRAs in determining prophylactic treatment management for latent tuberculosis (LTB) in Israel.

Methods: We analyzed the retrospective data of 367 subjects who were referred to our laboratory during the period 2007–2011 for QuantiFERON Test-Gold In Tube (QFT-GIT) tests because of suspected LTB. Demographics and clinical data were retrieved from a questionnaire at enrollment, and 166/367 (45%) were further interviewed by phone in order to complete follow-up information on prophylactic TB treatment. 

Results: The majority of subjects (116/166, 69.9%, P < 0.0001) were spared prophylactic treatment subsequent to QFT-GIT testing. Subjects with negative QFT-GIT and positive tuberculin skin test (TST) results who were BCG-vaccinated had the lowest treatment rates (6/68, 8.8%, P < 0.0001). Most BCG-vaccinated subjects with positive TST and negative QFT-GIT test results received treatment with anti-tumor necrosis factor-alpha (TNFα) (17/19, 89.5%, P = 0.004). We found more negative QFT-GIT test results in subjects who were receiving anti-TNFα or steroid and other immunosuppressive treatment prior to testing (11/11, 100%, P = 0.029; 22/26, 84.6%, P = 0.06; 15/17, 88%, P = 0.06, respectively). 

Conclusions: Deciding on LTB prophylactic treatment in Israel is highly influenced by QFT-GIT test results. QFT-GIT findings contribute to clinical decisions, but their interpretation must also consider the patient’s medical history and clinical characteristics. 

 

Abstract

Background: The mass influx of immigrants from tuberculosis-endemic countries into Israel was followed by a considerable increase in the incidence of tuberculosis (TB). All contacts of active TB patients are obliged to be screened by tuberculin skin tests (TST) and, if found positive, prophylactic treatment is considered.

Objectives: To assess the utility of interferon-gamma (IFNγ)-release assay with a prolonged follow-up in preventing unnecessary anti-TB therapy in individuals with suspected false positive results.

Methods: Between 2008 and 2012 the QuantiFERON TB gold-in-tube test (QFT-G) was performed in 278 sequential individuals who were mostly TST-positive and/or were in contact with an active TB patient. In all, whole blood was examined by the IFNγ-release assay. We correlated the TST diameter with the QFT-G assay and followed those patients with a negative assay.

Results: The QFT-G test was positive in only 72 (42%) of all 171 TST-positive individuals. There was no correlation between the diameter of TST and QFT-G positivity. Follow-up over 5 years was available in 128 (62%) of all QFT-G-negative individuals. All remained well and none developed active TB.

Conclusions: A negative QFT-G test may obviate the need for anti-TB therapy in more than half of those with a positive TST.

Background: The crowded environment of correctional facilities may enhance infectious diseases transmission, such as tuberculosis.

Objectives: To define the tuberculosis burden in prisons in Israel, a country of low TB[1] incidence (7.9 cases:100,000 population in 2004), in which about 13,000 inmates are being incarcerated annually, and to recommend policy adaptations for TB control.

Methods: All prison clinic lung records from 1998 through 2004 in Israel were reviewed to identify pulmonary TB patients. Additionally, we reviewed TB epidemiological investigation files from one northern prison (years 2002 through 2005) to evaluate possible transmission of the disease.

Results: During the study period 23 Israeli inmates had pulmonary TB (25 cases/100,000 prisoners), which was 3.5 times higher than for the general population. Of those, 18 (78%) were born in the Former Soviet Union and immigrated to Israel after 1990. Four pulmonary TB cases in the evaluated prison were reported, and 22% (149/670) of all inmates and staff were referred for treatment of latent TB infection.

Conclusions: To prevent future TB cases, we recommend new prevention measures, including a symptom questionnaire for all new inmates and selective tuberculin skin testing for inmates infected with human immunodeficiency virus/AIDS, those who inject drugs, and those who emigrated from the former Soviet Union after 1990. New staff should be screened by the two-step tuberculin skin test and annual symptoms questionnaire thereafter. Incarceration may be used as a point of detection for TB and a window of opportunity for treatment in this hard-to-reach population. 

Background: One of the measures adopted in Israel since 1959 as part of the tuberculosis control program was screening children aged 12–13 years old. The screening comprised single-step tuberculin skin testing using the Mantoux method.

Objective: To assess the efficacy of tuberculin skin screening for TB[1] in schoolchildren in southwestern Israel as well as the compliance to treatment for latent tuberculosis infection.

Methods: We retrospectively reviewed the records of children in the Ashkelon region who underwent a tuberculin skin test during the period 1995–99.

Results: Of the 28,016 eligible children, 27,232 were tested. In 923 children, mostly from the former USSR and Ethiopia, an induration of 10 mm or more was found. Only 52 Israeli-born children tested positive. Tuberculosis was found in seven children with a positive test, five of whom were from Ethiopia. All children who tested positive were referred to the local TB clinic; only 266 children (28.8%) presented. Only 151 completed the recommended treatment of isoniazid for 6 months. Thus, although screening included most of the targeted children aged 13, only a third of them presented to a TB clinic, of whom only about half completed treatment of latent infection.

Conclusions: Our results indicate that the current policy of screening for latent TB in our region is ineffective in terms of implementation of the recommended treatment. We suggest that only high risk groups be screened, and that a concerted effort be made to implement treatment.

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