In human immunodeficiency virus (HIV), atypical findings are more common, including no changes despite active disease. Typical changes include air space consolidation, cavitation and fibrous contraction in one or both upper lobes or superior parts of the lower lobes ( Figure 2). Chest X-rayīoth posterior-anterior (PA) and lateral films are important with clear notes to the radiologist. These patients are potentially infectious so precautions should be used. Patients with symptoms suggestive of active TB (such as night sweats, cough and fever) require chest X-ray and microbiological testing. immune modulators, chemotherapy and post-transplantation) Immunocompromised states including HIV infection (risk of TB reactivation is 10% per annum 4 although this is substantially reduced with antiretroviral therapy 12).Recently acquired infection – particularly within the first 2 years.Investigations when considering a diagnosis of TB Table 2. Healthcare workers who have been working in high burden countriesįigure 1.Migrants or refugees from high TB-burden countries, particularly refugees from sub-Saharan Africa and students from India, China and other Asian countries.Torres Strait Island residents – from exposure to Papua New Guinean residents (where the incidence of TB and MDR-TB is high) 11 crossing the border.Elderly patients – the incidence was far higher in the mid-20th century, particularly postwar European migrants and refugees from the Vietnam war. Populations at increased risk of exposure to TB A flowchart detailing how to investigate when considering a diagnosis of TB is shown in Figure 1. When to consider TBĪs presentations may be atypical, TB should always be considered, particularly in populations at high risk of TB exposure ( Table 1) or of TB reactivation ( Table 2). 1 Other sites of infection include lymph nodes, pleural space, bone and joints, genito-urinary and meninges. Tuberculosis is classically a pulmonary disease, but 39% of Australian notifications in 2007 were extrapulmonary infections. Once reactivated, symptoms such as fever, night sweats, weight loss and cough develop, typically for 2–3 weeks or more. Overall, a person with LTBI has a 10% risk of developing active TB during their lifetime, with the greatest risk being within 2 years of infection. This is termed 'latent tuberculosis infection' (LTBI). When infection is contained by the immune system it remains dormant, usually within the lung apices. Primary infection may also manifest as pneumonia or pleural effusion. Occasionally (and particularly in children), infection disseminates resulting in TB meningitis or miliary TB. Household contacts of a confirmed case of TB require assessment.įollowing exposure and inhalation of airborne tubercle bacilli, cellular immune defences usually contain the infection so patients do not become acutely unwell. Tuberculosis is a notifiable disease in Australia, by both laboratories and clinicians. Other mycobacterial species may cause infection but are not contagious, require different treatment and should not be termed tuberculosis. bovis (bovine TB) are also responsible for infection, although these are uncommon in Australia. Tuberculosis is caused by infection with strains of the mycobacteria complex, typically MTB. This article outlines how each test can contribute to a diagnosis of TB, although a key diagnostic challenge is still to 'remember TB'. For active TB, chest X-ray and microbiological tests are required. Latent TB infection is diagnosed by detecting specific immunological responses to Mycobacterium tuberculosis (MTB) proteins using interferon gamma release assays or tuberculin skin testing. Testing for TB varies according to the stage of disease. After infection, TB may remain latent for many years, re-emerging with immunosuppression or advancing age. Patients born, raised or recently arrived from high TB-burden countries, and patients from some indigenous communities, are at much higher risk of contracting TB.
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