Abstract
Case finding and the diagnosis of tuberculosis (TB) are key activities to reach the World Health Organization’s End TB targets by 2030. This paper focuses on the diagnosis of pulmonary TB (PTB) in low- and middle-income countries. Sputum smear microscopy, despite its many limitations, remains the primary diagnostic tool in peripheral health facilities; however, this is being replaced by molecular diagnostic techniques, particularly Xpert MTB/RIF, which allows a bacteriologically confirmed diagnosis of TB along with information about whether or not the organism is resistant to rifampicin within two hours. Other useful diagnostic tools at peripheral facilities include chest radiography, urine lipoarabinomannan (TB-LAM) in HIV-infected patients with advanced immunodeficiency, and the loop-mediated isothermal amplification (TB-LAMP) test which may be superior to smear microscopy. National Reference Laboratories work at a higher level, largely performing culture and phenotypic drug susceptibility testing which is complemented by genotypic methods such as line probe assays for detecting resistance to isoniazid, rifampicin, and second-line drugs. Tuberculin skin testing, interferon gamma release assays, and commercial serological tests are not recommended for the diagnosis of active TB. Linking diagnosis to treatment and care is often poor, and this aspect of TB management needs far more attention than it currently receives.
Highlights
Tuberculosis (TB), despite being an ancient disease that has affected mankind for thousands of years, remains a huge global public health threat
Conventional mycobacterial culture and second-line drug susceptibility testing or molecular line probe assays performed in national reference laboratories are the only ways of obtaining this information, but the new molecular technology assay described earlier may change this in the future and allow these diagnoses to be made at more peripheral levels of the health system
In 2016, World Health Organization (WHO) recommended in patients with a sputum smear-positive specimen or a cultured isolate of Mycobacterium tuberculosis (MTB) that a commercial molecular Line Probe Assays (LPA) be used as the initial laboratory test instead of phenotypic DST to detect resistance to rifampicin and isoniazid [57]
Summary
Tuberculosis (TB), despite being an ancient disease that has affected mankind for thousands of years, remains a huge global public health threat. The goal of the End TB Strategy is to end the TB epidemic, the targets for meeting this goal being 90% reduction in TB deaths and 80% reduction in TB incidence by 2030 compared with 2015, with no affected families facing catastrophic financial costs (Table 1) While these successive strategies have resulted in huge progress and millions of deaths averted [2], major challenges still loom large. This paper focuses on progress made and challenges faced with case finding and diagnosis of PTB in low- and middle-income countries (LMIC) It focuses first on district hospitals and peripheral health facilities and discusses the systems of sending sputum specimens to and the use of national reference laboratories for drug susceptibility testing for first- and second-line drugs. The authors recommend that point-of-care molecular technology is the best way forward for diagnosis if we are to meet the ambitious goal of ending TB by 2030
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