Ten years Trend in Adult Tuberculosis Diagnosis in a Southern Union Territory of India. A Public Health view.

India has the highest number of Tuberculosis patients, globally [1–3]. The nation is committed to eliminate Tuberculosis (TB) by 2025 [4]. An important strategy to eliminate TB involves improving the notification rate of TB in India. In 2018, India notified 21.5 lakh cases, while the World Health Organization (WHO) estimates were at 27 lakhs [4]. Few strategies were adopted recently to improve the notification – public private partnership where private medical practitioners and private diagnostic labs were sensitized to notify Tuberculosis to the public health system; introduction of modern diagnostic tools, the latest being the Cartridge Based Nucleic Acid Amplification Test (CbNAAT) and True-NAT; and the active case finding of Tuberculosis in the community [3,5,6]. As a part of studying the impact of CbNAAT on the national health programme, the principal investigator (PI) analysed ten years of Tuberculosis notification data (2010 to 2019) of a Union Territory (UT) in southern India having a population of nearly 14 lakhs. After ethics clearance (Ref No – RC 17/98), Ethics Advisory Group of The Union, Paris, France (No 94/17), and the National Tuberculosis Elimination Programme (NTEP) office of State Government (PSHM/RNTCP/acc/S2/2017-18/239) data were retrieved from the programme office. An important finding was a drastic decrease in trend of clinically diagnosed Tuberculosis among adults. The trend of total TB notification remained same for ten years even after the introduction of newer tools, however, the clinically diagnosed TB notification among adults reduced from 21% (CI 19%-23%) to 3% (CI 2%-4%) (Figure 1: Adapted and modified from the original source by the PI) [8].

The reasons for this drastic decline in clinically diagnosed TB could be – in the recent years there has been a stress on microbiologically confirmation of Tuberculosis. On these lines, initially, a liquid culture followed by Line Probe Assay (LPA) was introduced in 2012. Later, the CbNAAT was introduced in 2016 in the UT under study, this may have increased the microbiologically confirmed cases and helped reducing the clinically confirmed cases [2,3,7,8]. Even though newer techniques have lot of advantages in diagnosing TB faster, on the other hand it also has few limitations. While interpreting the CbNAAT, physicians should note the following things – CbNAAT is highly sensitive for sputum positive cases but its sensitivity decreases when it comes to sputum negative but culture confirmed TB (68%) and for extrapulmonary TB (44% to 85%) [9]. Few physicians may falsely interpret 'CbNAAT negative means no TB’, this has been noticed in certain studies [8,10]. Ideally, after the introduction of modern diagnostic tools, the total TB notification should have been increased but it remained stationary [4]. This shows that modern techniques just replaced the clinical confirmation at present stage.

A lesson from this trend is that physicians should be cautious before ruling out TB among symptomatic patients. They should interpret the results in the light of sensitivity and specificity of that particular test and the site of sample collection, and at any point of time their clinical diagnosis is still valuable as per the Revised National Tuberculosis Control Programme – Technical Operational Guideline (RNTCP TOG guideline) - TB Diagnostic Algorithm [11].

References

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