Abstract
Public health problem and access issues related to diagnostics
The World Health Organization (WHO) estimates that, in 2013 alone, 9.0 million people fell ill with tuberculosis (TB) and 1.5 million died from the disease. Rapid, accurate diagnosis is critical for timely initiation of treatment, but many people with TB do not have access to adequate initial diagnosis. In 2013, only 6.1 million TB cases were notified to national TB programmes (NTPs). The remaining 3 million cases were either not diagnosed, or not notified to NTPs. In 2013, 58% of the 4.9 million pulmonary TB (PTB) patients notified globally were bacteriologically confirmed via a WHO-recommended test, including rapid tests such as Cepheid Inc.’s GeneXpert® MTB/RIF (Xpert® MTB/RIF). The rest were likely managed on the basis of clinical suspicion or non-specific tests (e.g. chest x-rays [CXRs]). Access to diagnosis is particularly challenging in people with multidrug-resistant (MDR) TB and in children with TB. Globally, in 2013, WHO estimated that 480 000 people developed MDR TB. It is estimated that 136 000 of the estimated 300 000 MDR TB patients who could have been detected were diagnosed and notified. This was equivalent to almost one in two (as compared to one in six in 2009). Some of this progress in the detection of drug-resistant TB has been attributed to the use of rapid molecular diagnostics such as line probe assays (LPAs) and Xpert® MTB/RIF. Recognizing the critical importance of drug susceptibility testing (DST), the End TB Strategy, published in 2015, includes universal DST as a key component of its first pillar: integrated, patient-centred TB care and prevention. In 2013, an estimated 550 000 children became ill with TB, but the true case burden of childhood TB is likely higher than estimated. Childhood TB is notoriously difficult to diagnose, and most conventional TB tests perform poorly in this vulnerable population.