Rapid point-of-care test shows promise for detecting latent tuberculosis

A new test shows promising results for detecting latent tuberculosis infection in resource-limited settings. This is according to a study from Karolinska Institutet, published in the journal Clinical Infectious Diseases.

Tuberculosis remains one of the world's deadliest infectious diseases. To reduce the number of new cases, infected individuals with latent infection must be detected and offered preventive treatment to avoid active tuberculosis, which can spread the disease to others.

Currently, latent tuberculosis is often diagnosed using a laboratory test called QuantiFERON-TB Gold Plus. This test involves several steps and can take one to two days before the results are available, as well as requiring advanced laboratory infrastructure and trained personnel. This makes it difficult to carry out tests in areas with a high prevalence of tuberculosis where access to laboratories and trained personnel is limited.

In the new study, researchers from Karolinska Institutet in Sweden, together with colleagues in Vietnam, have therefore compared this test with another test, TB-Feron. This is a point-of-care test that provides results within 15 minutes and does not require an advanced laboratory or trained personnel.

The study included 345 adult participants in Hanoi, Vietnam, divided into three groups: people with confirmed tuberculosis, people in the same household as people with infectious tuberculosis, and people with no known exposure to tuberculosis. All were tested with both TB-Feron and the established laboratory test QuantiFERON-TB Gold Plus.

The results show that TB-Feron has high sensitivity - 88 percent of individuals with expected positive results were correctly identified. The corresponding figure for QuantiFERON-TB Gold Plus was 92 percent.

However, the specificity, i.e. TB-Feron's ability to rule out tuberculosis infection in healthy individuals, was moderate at 70 percent. The corresponding figure for QuantiFERON-TB Gold Plus was 96 percent.

Among household contacts, the concordance between TB-Feron and the established test was good, with 92 percent concordance for positive samples.

It is promising that TB-Feron works so well in an environment with a high disease burden. The test is patient-friendly and easy to use, with rapid same-day results, making it useful in primary care."

Han Thi Nguyen, pulmonologist and doctoral student at the Department of Medicine, Solna, Karolinska Institutet, and first author of the study

The researchers also investigated the reliability of TB-Feron by comparing results from two different groups with laboratory staff. No systematic differences were observed, indicating good reproducibility.

"This test can help more people with latent tuberculosis to be detected and receive preventive treatment, especially in rural areas in countries with limited resources," says last author Lina Davies Forsman, a researcher at the same department.