​​​​​“There is an urgent need for new diagnostic tests for tuberculosis (TB). Particularly point-of-care tests (POCT) for all types of TB, that work in both adults and children," Dr Novel Chegou said in his state-of-the-art lecture at the recent Annual Academic Day at the Faculty of Medicine and Health Sciences (FMHS), Stellenbosch University (US). “Ideally you would want a TB test that is easy to use by frontline health workers, requires no instruments, is finger-prick based, takes five minutes to produce a result and is cheap – under $1."

Chegou is a Senior Researcher with the Immunology Research Group in the FMHS' Division of Molecular Biology and Human Genetics, and was presenting on his work on TB biomarkers that aims to develop a novel, effective TB diagnostic tests.

This is a huge need globally in the field of TB and one that Chegou and his team are eager to address. “There were 10,4 million cases of TB and 1.7 million adult deaths in 2016. Seven countries, including South Africa, account for 64% of cases, and TB is one of the top nine causes of death globally. At a high-level meeting in 2014 the World Health Organisation (WHO) identified the development of new tests as a major priority," Chegou said.

“There is a need for a quick and easy diagnostic test," he continued. “Smear microscopy is still the most widely used test worldwide, but has several limitations. Culture remains the gold standard but is expensive and the turnaround time is long. Serological assays are also used by about a quarter of laboratories that responded to a recent worldwide survey - they are easier to perform and more rapid, but are not recommended by the WHO."

“As much as 15-20% of TB is extra-pulmonary and difficult to diagnose," added Chegou, “and sputum-based testing is particularly difficult in children who are not necessarily able to produce sputum."

“Ideally, in resource-constrained settings like ours you would want an effective POCT to use at the entry point in the healthcare system for people who present with symptoms and need quick referral for gold standard tests or for treatment. Tests that can be used by community health workers with minimal training."

A strategy involving testing at the POC and quickly referring only patients with positive POC tests for further testing with confirmatory tests such as the GeneXpert and culture will be beneficial to both the patient and the healthcare system as it will avoid unnecessary expensive tests on all patients suspected of having TB. This will lead to cost savings for the health care system and more rapid initiation of both TB patients and patients with negative POC test results on appropriate treatment. 

Chegou originally trained in Cameroon and completed his post-graduate studies in tuberculosis immunology at US. He is currently working on biomarkers for TB diagnosis, biomarkers of protective immunity against TB for vaccine development and biomarkers for monitoring TB treatment.  However, he is particularly interested in the development of simple, field-friendly POCT diagnostic tests for the rapid diagnosis of TB disease and monitoring of the treatment response. He is listed as an inventor on seven patent applications on diagnostic biosignatures for TB disease.

The group's seven-marker serum biosignature has been adapted into a finger-prick-based screening test and is now being tested for accuracy and efficacy in a study called ScreenTB involving 700 - 800 participants with suspected active TB across five African countries. The study commenced in 2016 and results are expected by 2019.

The work is being done as part of the “ScreenTB Consortium" (www.screen-tb.eu), which is a continuation of a previous consortium called “African European TB Consortium" with funding from the European and Developing Countries Clinical Trial Partnership (EDCTP). The group is also developing a similar test for the diagnosis of tuberculous meningitis, in collaboration with the Engineering Department at US.

“The preliminary results are promising but we still need to optimise and simplify," said Chegou. “Future work would involve multi-centre trials to evaluate efficacy and to compare to other tests as well as looking at using the same test for children."

Photo by Damien Schumann