Positive and negative tb test skin#

Positive and negative tb test skin#

Several factors have been cited as confounders of the TST skin test. Although this guideline assigns patients with RA who are being treated with immunosuppressive drugs to the group of patients who are at high risk of developing active TB, it defines neither the dose nor the duration for immunosuppressive treatments, and it only mentions high-dose treatments for patients treated with steroids. According to the Centers for Disease Control and Prevention guidelines, an induration of ≥ 5 mm is classified as positive in the following groups: patients with HIV infection, patients who had recent close contact with TB infected people, patients who have undergone organ transplants or who are receiving immunosuppression therapy (e.g., TNF-i, methotrexate, prednisone, and cyclosporine), and patients whose chest radiographs show fibrotic changes consistent with previous TB. However, its accuracy among certain patient groups is questionable. Until about 10 years ago, the tuberculin skin test (TST) was the only test available to detect LTBI. Although the introduction of tumor necrosis factor alpha inhibitors (TNF-i) for the treatment of RA represents a significant advance in this area, the therapy is associated with an increase in the incidence of active TB disease among the population of RA patients. Patients with rheumatoid arthritis (RA) were found to have an increased incidence of TB infection in several studies, including a large observational cohort study from Japan that reported a 3.2-fold increased risk of TB in RA patients who were treated with the standard therapy of DMARDs. It is generally accepted that patients with systemic inflammatory diseases are susceptible to TB infection due to the suppression of their immune systems that can be caused by steroid or disease modifying antirheumatic drug (DMARD) treatment or by the presence of the disease itself. People with LTBI are asymptomatic, but they harbor Mycobacterium organisms that can be reactivated and cause disease under certain circumstances associated with known risk factors.

Although the human immune response is highly effective at controlling the initial infection with Mycobacterium tuberculosis, in some individuals, all viable organisms may not be eliminated, which leads to a latent tuberculosis infection (LTBI). With almost 8 million new tuberculosis (TB) cases reported annually, TB morbidity and mortality remain major problems in the world.