Despite global screening and monitoring efforts, tuberculosis (TB) remains a major public health burden, including in India. Following the publication of a nationwide evaluation of essential TB diagnostics, Mustafa Barbhuiya discusses the gaps between national policy and point-of-care access – and what laboratories and healthcare systems must do to support TB elimination.
What are the main gaps in access to essential TB diagnostics identified by your study?
The central finding is that India does not simply face a shortage of TB diagnostics. There is also a mismatch between where diagnostic capacity is located and where patients first seek care.
We assessed 327 public healthcare facilities across seven states and Delhi, including subcenters, primary health centers (PHCs), community health centers (CHCs), and district hospitals. The largest gaps occurred at the primary-care level. Although India’s National Essential Diagnostics List recommends both acid-fast bacilli (AFB) smear microscopy and chest X-ray at PHCs, complete availability generally ranged from only 0 to 10 percent across the regions surveyed.
Across the healthcare tiers where each test is recommended, AFB microscopy was available in approximately 78 percent of facilities. Chest X-ray and cartridge-based nucleic acid amplification testing (CBNAAT) were each available in around 51 percent, while fluorescence microscopy was present in approximately 31 percent of the district hospitals assessed.
We also identified a national shortfall in culture and drug-susceptibility testing (CDST) capacity. Based on the recommended ratio of CDST laboratories to TB treatment units, India would require an estimated 283 laboratories, compared with the 97 identified in our analysis – a shortfall of 62 percent.
India has a national TB program and modern diagnostic technologies. The challenge is translating these resources into equitable access, particularly for rural, remote, and underserved populations.
How is TB currently diagnosed in India, and how does this compare with diagnostic practice in Western countries?
India has a tiered diagnostic system under its National Tuberculosis Elimination Program. Sputum collection and smear microscopy remain important at the peripheral level, while chest radiography and molecular testing are intended to become increasingly available at PHCs, CHCs, and higher-level facilities. CDST is concentrated within specialized laboratory networks.
However, our study identified a gap between the recommended pathway and what patients can access at the point of care. The World Health Organization (WHO) recommends rapid molecular diagnostics as initial tests for people with presumptive TB, but molecular testing in India remains disproportionately concentrated at secondary and higher levels of care.
I would be cautious about treating “Western countries” as a single diagnostic model because practices vary between healthcare systems. In well-resourced systems such as the United States and United Kingdom, however, patients with suspected pulmonary TB generally have more consistent access to chest imaging, microscopy, molecular testing, culture, and drug-susceptibility testing.
The main difference is therefore less about scientific knowledge than diagnostic-system capacity. A test is useful only when the patient can access it, the specimen can reach the laboratory, the result is returned promptly, and clinicians can act on the findings.
Why do many facilities still rely on smear microscopy, and what are its limitations?
Our study showed continued reliance on AFB smear microscopy, although it was not designed to identify every reason for this dependence. The explanation is understandable: microscopy is relatively inexpensive, familiar to laboratory professionals, does not require advanced molecular infrastructure, and has been embedded in TB programs for decades.
However, availability should not be confused with adequacy. Smear microscopy is less sensitive than contemporary molecular testing. WHO notes that conventional microscopy generally requires around 5,000–10,000 bacilli per milliliter of sputum to detect disease reliably. Its performance is therefore limited in patients with low bacterial loads, including some people living with HIV.
Microscopy also cannot determine whether the organism is drug-susceptible or drug-resistant. A patient may have TB despite a negative smear. If the diagnostic pathway ends there, the disease may be missed or diagnosed late, transmission may continue, and appropriate treatment may be delayed.
For these reasons, WHO recommends rapid molecular diagnostics as initial tests for presumptive TB. Smear microscopy continues to have a role, including in some monitoring settings, but it should not remain the upper limit of diagnosis because a patient lives far from an advanced laboratory.
What needs to change to improve access to rapid molecular tests, chest X-rays, and CDST?
The first priority is to stop viewing these technologies as isolated tests and instead build a connected diagnostic network.
Rapid molecular testing should be expanded systematically at CHCs and, where feasible, brought closer to PHCs. Where onsite testing is impractical, reliable specimen-referral and transport systems are essential. Our study found considerable variation in CBNAAT availability at CHCs, with several surveyed regions reporting coverage of only 10 to40 percent.
Chest radiography must also become genuinely accessible at the primary-care level. Despite its inclusion in India’s National Essential Diagnostics List, X-ray availability at PHCs generally ranged from 0 to 10 percent. Portable digital systems could help extend access, particularly in remote regions.
Computer-aided detection could support TB screening where radiologists are scarce. WHO recognizes this software for interpreting chest X-rays in people aged 15 years and older and identified six products meeting its performance standards in 2025. However, X-ray and AI are screening or triage tools – not substitutes for bacteriological confirmation, clinical judgment, or a properly designed diagnostic pathway.
India also needs greater CDST capacity. Expanding molecular screening without strengthening culture and susceptibility testing could create a downstream bottleneck. This does not mean placing a culture laboratory in every PHC. Culture requires containment facilities, specialist expertise, quality systems, and appropriate biosafety measures. Patients instead need timely access through a functioning hub-and-spoke laboratory and specimen-transport network.
How can laboratories extend diagnostic services to remote and underserved communities?
Greater regulatory coordination between India’s state and national agencies is an important starting point. Mismatched requirements and administrative inefficiencies can discourage private laboratories from expanding into highly regulated areas such as TB diagnostics.
We also need to redefine laboratory access. It does not necessarily mean building a fully equipped laboratory beside every patient. It means ensuring that geography does not determine diagnostic quality.
A practical model could combine local sputum-collection points, portable or mobile radiography, rapid molecular testing at strategically located hubs, scheduled specimen transportation, electronic reporting, and defined referral pathways to CDST laboratories.
Our fieldwork offers an important lesson. Many sites surveyed in northeast India were remote and logistically challenging, yet they remained accessible when we worked with local collaborators who understood the geography and communities. Remote populations are not inherently unreachable; health systems must be designed to reach them.
Technology provides value only when a patient with an abnormal screening result is connected promptly to molecular testing, clinical assessment, treatment, and follow-up. The final mile of diagnosis is therefore not simply a technology problem; it is a laboratory-network and healthcare-delivery problem.
What role should molecular testing play in detecting TB and drug resistance?
Molecular testing should become central to the early diagnostic pathway. WHO recommends approved rapid molecular tests as initial diagnostics for appropriate patients with presumptive pulmonary TB rather than relying on conventional microscopy.
These assays can identify Mycobacterium tuberculosis more quickly and sensitively than smear microscopy. Some platforms can also detect clinically important resistance markers. This changes the clinical question from simply, “Can I see acid-fast bacilli?” to “Is M. tuberculosis present, and is there evidence of resistance to important drugs?”
That distinction is particularly important for India, where drug-resistant TB remains a major public health challenge. However, molecular testing is not equivalent to comprehensive drug-susceptibility testing. Molecular assays detect predefined genetic targets, meaning that emerging or uncommon resistance mechanisms may fall outside their scope.
Culture-based phenotypic testing will therefore remain important, while targeted next-generation sequencing is expanding the ability to characterize resistance. The future should not be framed as molecular testing versus culture. We need a layered system that uses rapid molecular testing for early detection and initial resistance assessment, supported by CDST and sequencing for complex, discordant, recurrent, and drug-resistant cases.
What investment is needed to close diagnostic gaps?
Investment must support the entire diagnostic ecosystem, not simply the purchase of instruments.
India needs molecular platforms, digital radiography, appropriately distributed CDST laboratories, biosafety systems, stable electricity and connectivity, equipment maintenance, quality-assurance programs, and reliable supplies of cartridges and reagents.
Investment in people is equally important. Laboratory professionals require continuing training in molecular diagnostics, mycobacteriology, biosafety, quality management, drug-resistance testing, genomic technologies, and digital systems. Installing an advanced instrument without trained personnel, maintenance, quality control, or clinical integration does not create diagnostic capacity.
Referral networks must also become an explicit part of diagnostic policy. A specimen collected at a remote PHC should have a predictable route to the appropriate laboratory, supported by defined transport schedules and turnaround-time standards. The result must then reach the treating healthcare professional quickly enough to influence patient management.
TB diagnosis also cannot be separated entirely from treatment monitoring. Complete blood counts and metabolic testing help identify hematological, hepatic, renal, nutritional, and other complications associated with the disease and its treatment. However, these services were also inconsistently available at peripheral facilities.
I would summarize the required investment in three words: availability, connectivity, and quality. India already has advanced diagnostic science, skilled professionals, and considerable technical expertise. The next challenge is making those resources geographically equitable.
If the goal is TB elimination, the right test must reach the right patient at the appropriate point in the clinical pathway – not simply exist somewhere within the healthcare system. That is the difference between possessing diagnostic technologies and providing meaningful diagnostic access.
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