India has roughly 1.3 million “missing” tuberculosis (TB) patients, who may either not have been diagnosed or were lost for follow-up, and so could potentially spread TB to others, according to a new study1.

For a country already burdened with one quarter of the world’s TB patients, these are worrying new findings by an international team of researchers, including TB experts from major institutes in India.

Using a model called the “cascade of care”, the study aimed to systematically estimate how many TB patients in India’s national TB programme are not being detected, not enrolling for treatment, not completing treatment, and are alive without TB recurrence one year after finishing treatment.

This step-by-step analysis, the researchers said, is a useful model to identify gaps in healthcare delivery that need to be plugged by India’s TB Control Programme to achieve its revised goal of “universal access to quality care” for all TB patients.

For their analysis, the researchers collected data from multiple official reports published by the World Health Organization and India’s national TB programme and also from relevant medical literature published during 2000-2015.

According to the study, out of about 2.7 million Indians with TB in 2013, only about 1.05 million, or 39%, completed therapy in the government TB programme and did not have relapse for one year after stopping treatment. Out of 61, 000 difficult to treat multidrug-resistant (MTR) TB patients, only 11% completed treatment.

The worrying part of the study was the finding that 760, 000 TB patients never reached government clinics and another 500, 000 patients were evaluated at the clinics but were either not diagnosed with TB or not put on treatment after diagnosis. Together they constitute the group of "missing" TB patients who can potentially spread the disease to others.

Considerable proportion of these “missing” patients are being treated by private sector including practitioners of Indian medical traditions "who often have no formal medical degrees," the researchers said.

"A key conclusion is that India's TB programme will need to find more resources and address the gaps," the authors said adding that "increasing detection and diagnosis by using new diagnostic tests may be the most important intervention for improving patient outcomes, especially MDR TB patients."

Since many patients experience relapse of the disease, "routine follow-up after completion of TB therapy may be an efficient approach for identifying new TB patients."

Their findings highlight the need for more engagement of the government TB programme with private providers, including collaborative efforts and incentives to promote referral of TB patients.

The authors note their study did not cover the private sector. "We know private sector manages a lot of TB in India," Madhukar Pai, Associate Director of International TB Centre at McGill University and one of the authors told Nature India . "A similar cascade of care analysis to identify critical gaps in the private sector would be most helpful and is urgently needed."