In 2009, a state-of-the-art automated system was launched by the World Health Organization to diagnose tuberculosis (TB) in samples, in just 90 minutes. While this technology has been rolled out in India, it has not yet reached a vast majority of Indians who suffer from TB — mainly due to the high associated costs. Now a new study published in the journal PLOS Medicine, led by Johns Hopkins Bloomberg School of Public Health and McGill University, suggests that correct and prompt diagnosis by the right doctors can be just as useful in tracking TB as the new diagnostic test, Xpert MTB/RIF.

TB, an infection of the lungs, is caused by the highly infectious and contagious Mycobacterium tuberculosis. An estimated 8.6 million people worldwide get infected with TB and 1.4 million die from it each year. Twenty-five percent of these cases are found in India, and in 2011 there were 300,000 TB-related deaths. While India’s National TB Control Programme is the largest of its kind in the world offering free and effective treatment, there are still millions who go undiagnosed.

Public TB clinics are best equipped to recognize and treat the disease, which must be caught early on for effective treatment, but patients are often reluctant to use them and prefer to get treated by private and informal health care providers. "Most people in India with underlying TB initially seek care for cough from the private health care sector," notes the study's lead author Dr. Henrik Salje in a press release. "Private providers often use the wrong tests for TB, and without getting the right diagnosis, patients move between providers with long diagnostic delays.”

The study therefore suggests that the new test for TB should be made available to private health care providers where patients first seek care. This new test for TB — Xpert MTB/RIF — simplifies the traditional methods of sample preparation, amplification, and detection by fully automating the three. It can diagnose TB in 90 minutes, capture 70 percent of cases missed by microscopy, and can also determine if the strain is resistant to rifampin, the most important anti-TB drug.

Currently, due to the high costs, it is only being used on the highest-risk populations and in public health clinics that test HIV-positive patients who may also have TB or those at high risk of having multidrug-resistant tuberculosis (MDR-TB). Physicians in the absence of this test still rely on the smear microscopy, which may miss up to half of all active cases.

In their study, the researchers analyzed the impact of six rollout strategies on the incidence of TB in India. They did this by developing a mathematical model of TB transmission, care-seeking, and diagnostic and treatment practices.

They found that providing access to Xpert for 20 percent of all individuals seeking care for TB symptoms could reduce new TB cases by 14.1 percent over five years, while the "high-risk-only," public-sector strategy currently being implemented might only reduce TB cases by 0.2 percent. But to achieve this there had to be substantially improved resources and better treatment practices.

The study also found that training the informal care providers to accurately diagnose TB in the public sector can have as much an impact on the incidence of TB as the new test would.

"The impact of better TB diagnosis depends not only on the accuracy of the test, but also on the behavior of both patients and providers, good access to validated new tools, and quality TB treatment following diagnosis," said the study's senior author, David W. Dowdy.

"To achieve maximum impact of novel diagnostics, India should engage the private sector, improve quality of care across all sectors, and dramatically increase the resources used to fight TB."

Source: Salje H, Andrews J, Deo S, The Importance of Implementation Strategy in Scaling Up Xpert MBT/RIF for Diagnosis of Tuberculosis in the Indian Health-Care System: A Transmission Model, PLOS Medicine. 2014.