Tuberculosis (TB) remains a serious public health problem in India. Chest X-rays are a key tool in the fight against TB, as a fast, low-cost, non-invasive screening tool that can detect signs of TB in the lungs. But using them to diagnose TB and prescribe treatment, without further confirmatory tests may be putting patients at risk. We need alignment on how chest X-rays are used across India for TB screening, if we are to reach ambitious plans to eliminate TB by 2025 and prevent unnecessary deaths from this curable and preventable disease.
Worryingly, nearly 3 million people still contract TB each year across the country. Finding people with TB and making sure they start, and complete, effective treatment is critical. Among people who do not begin treatment, the disease kills around 50% of those affected. India is also home to an estimated 1 million “missing” people with TB, who remain undiagnosed and unknowingly spread the disease through their communities, undoing the progress in controlling TB.
A range of diagnostic tools and approaches are needed to find those affected by TB early in the disease and make TB elimination a reality for India. This includes tools to screen and confirm TB cases and identify patients with drug-resistant TB. We also need tests that work for people who are at greatest risk of TB and in certain groups where TB is harder to diagnose – this includes people living with HIV, children and those with co-morbidities. Also needed are tools that allow us to identify people with “silent” TB infections, before the disease develops into the active, more dangerous forms of TB.
Three main types of tests are recommended by India’s National TB Plan to screen for and diagnose pulmonary TB in adults: chest X-ray, sputum microscopy and rapid molecular tests. Screening people based on symptoms remains the mainstay for identifying those affected by TB, but its subjective approach misses many people with TB, particularly those earlier on in the disease who may not have distinctive symptoms. Government guidelines recommend increasing the use of rapid molecular tests to diagnose TB, including for all patients at risk of multi-drug resistant TB and to determine drug-resistance to the antibiotic rifampicin, a key treatment for TB.
In this context, chest X-rays are important as non-invasive screening tools that can give physicians a quick indication of whether person may have TB. However, chest X-rays are non-specific – i.e. abnormalities seen on a chest X-ray can suggest TB but can’t be used to exclude other diseases that also cause similar radiological features. Consequently, chest X-rays suggestive of TB should be followed by an approved rapid molecular test to confirm TB and to detect drug resistance, so doctors can prescribe an effective anti-TB drug regimen.
Evidence suggests that despite guidelines, physicians often start patients on anti-TB treatment based on chest X-ray findings alone. This practice is quite prevalent in India’s private sector, where over 50% of people with TB first seek care. A recent study showed that 1 in 5 people seeking TB care in the private sector in India were prescribed anti-TB drugs based on an abnormality on chest X-ray alone. Providers in the private sector may also prioritise turnaround time and may fear losing patients while waiting for a test result. Molecular tests can also be prohibitively expensive in the private sector, a cost passed onto the patients, who often cannot afford them.
The practice of prescribing prior to a confirmed TB diagnosis leads to inappropriate treatment prescriptions. In turn, this translates into suboptimal treatment, i.e. ineffective drug regimens which result in poor clinical outcomes for patients and increases their risk of developing drug-resistance. Ineffective treatment also ultimately leads to elevated costs for both patients and the health system.
Chest X-rays, when used appropriately, can help identify patients with a higher likelihood of TB disease, thereby limiting the use of rapid molecular tests – ultimately allowing the detection of more TB cases at lower costs. Chest X-rays have also been shown to have an advantage in the detection of “subclinical” TB. With subclinical TB, patients don’t report the typical TB symptoms (e.g. persistent cough, fever, night sweats or weight loss) but are still capable of transmitting the infection to those around them and still require treatment.
Newer technologies can overcome some of the challenges associated with standard chest X-ray interpretation. Computer-aided detection software leverages the power of artificial intelligence to make it easier to detect TB from chest X-rays. The recent introduction of portable handheld X-ray devices can also enable large-scale, community-based screening programmes in high TB-burden countries such as India. Portable X-ray devices can also complement the use of rapid molecular diagnostics to increase access to TB testing in community settings, bringing testing closer to people.
As an insidious and pervasive disease, tackling TB requires a multipronged approach to screen, test and effectively treat those affected. We have an arsenal of tools at our hands, as well as emerging advances such as portable molecular devices and digital chest X-rays with computer-aided detection software. However, tools must be accessible when and where they are needed, with clear guidance on how each should be used to have the greatest impact. It’s also important that resources from across the public and private sectors are leveraged to close gaps in TB detection and management. Ultimately, eliminating TB as a public health problem in India will depend on us implementing larger, more effective screening and testing strategies to find the missing TB cases, and reduce suffering from this deadly disease.
This article is authored by Dr. Sarabjit Chadha, regional technical director, India and SE Asia and Dr. Kavindhran Velen senior scientist, TB Access at FIND.