DIAGNOSING TUBERCULOSIS: TO END IS TO BEGIN

By: Adhella Menur

Watching the record of Prof. dr. Bachti Alisjahbana, Sp.PD-KPTI, Ph.D.’s scientific oration and reading Gustiani’s report of her TB biomarker laboratory training in Brazil brought me back to my time as a Research Assistant (RA) for the TRIPOD study (Tuberculosis Research of INA-RESPOND on Drug Resistance). In 2017, I transitioned from working as a general practitioner in a remote district hospital and a part-time private clinic to a top-tier referral hospital in Central Java. The difference was striking, with complete laboratory facilities and a full team of specialized doctors—luxuries not often found in remote areas. In TRIPOD, we enrolled presumptive TB patients and performed a range of microbiological tests, including acid-fast bacilli (AFB) staining, Xpert MTB/RIF assays, Mycobacterium tuberculosis (MTB) cultures, and phenotypic drug susceptibility testing (pDST). As an RA responsible for enrolling and following study participants and collecting biological samples, I gained firsthand insight into the complexity of TB diagnosis.

For many patients, the journey to a TB diagnosis was tiresome even before treatment began. Most came from moderate to low socioeconomic backgrounds, relied on national insurance, and lived far from our hospitals. They had to undergo hospital administration, meet insurance requirements, and wait in long queues with many other patients. Often, a single visit consumed an entire day, and further visits were needed for additional examinations. Even though medical costs were covered, non-medical expenses could still be a burden, especially for the family’s breadwinner. When family and work environments lacked support, patients usually felt overwhelmed and sometimes abandoned the diagnostic process. Many opted for private clinics or alternative medicine to relieve their symptoms. Collecting sputum was also difficult for some patients. Sometimes, the nurse would give patients a container and mucolytic drugs, instructing them to bring back a morning sputum sample. Unfortunately, if patients couldn’t produce a sample or faced difficulties, they often didn’t return. Additionally, with limited knowledge about TB, some patients hesitated to provide sputum, fearing a confirmed diagnosis would lead to long-term treatment, lost jobs, and social stigma.

I also observed the high workload clinicians, nurses, and laboratory technicians face. The unbalanced ratio of clinicians to patients often led to limited engagement. Nurses had to work hard to care for and counsel patients. The limited TB referral laboratories and technicians contributed to long turnaround times for testing results. In 2017, Xpert MTB/RIF testing was still limited to referral hospitals and was primarily used only when there was suspicion of drug-resistant (DR) TB. Additionally, at that time, Indonesia had only 11 certified laboratories for TB culture and nine for phenotypic drug susceptibility testing (pDST) to serve the large number of TB cases across the country. Fortunately, with the commitment to End TB, the government has enhanced case-finding and early TB diagnosis efforts. As AFB testing is less sensitive and specific for diagnosis and cannot detect drug resistance, Xpert MTB/RIF has now become the frontline tool for TB diagnosis. By 2023, there were over 2,000 Xpert MTB/RIF nationwide, with around 1,200 available at primary healthcare centers (Puskesmas). Also, there were 22 certified laboratories for MTB culture, 13 for pDST, and seven for line probe assays (LPA).

However, the diagnosis gap remains significant. In 2023, out of the estimated 1,060,000 people who developed TB in Indonesia, only around 820,000 were diagnosed and reported to national TB programs, leaving 23% undiagnosed. While there are promising advancements in short oral anti-TB drug regimens, these breakthroughs cannot reach their full potential without effective diagnosis. I came across an insightful commentary by Madhukar Pai et al. in Nature Microbiology in 2023, which discussed seven critical transitions needed to close the TB diagnostic gap. These transitions are interlinked, and their integration could have a significant impact. The commentary aligns well with Prof. Bachti’s views, who emphasized the importance of molecular-based TB assays, active case finding, embracing private services in diagnosing and managing TB, discovering more convenient samples than sputum, and innovating point-of-care testing (POCT).

Speaking about non-sputum biomarkers for TB diagnosis, intensified research and innovation in this field have been identified as essential components of the World Health Organization’s (WHO) End TB Strategy. Excellent biomarkers will be highly beneficial for diagnosing TB in challenging populations, such as children, people living with HIV, those with extrapulmonary TB, and individuals with subclinical TB. A promising advancement in this field is the use of the host transcriptome as a biomarker to detect disease states. This involves measuring the expression levels of mRNAs derived from blood samples, reflecting the genes actively expressed at a given time. Several studies are underway to discover and validate transcriptomic signatures in clinical trials.

In 2016, Sweeney et al. identified a TB score based on blood mRNA expression levels of three expressed genes: guanylate binding protein 5 (GBP5), dual specificity phosphatase 3 (DUSP3), and Krüppel-like factor 2 (KLF2), which are highly diagnostic for active tuberculosis. Excitingly, these three gene sig-natures have been incorporated into an automated qPCR test using the GeneX-pert platform (Cepheid, USA). This Xpert MTB Host Response (MTB-HR) prototype quantifies the expression of the three transcripts in a whole-blood sample and computes a TB score based on cycle threshold (Ct) values using an in-built algorithm. Even more exciting is the development of the test using a fingerprick whole blood sample of only about 200 μL, rather than pricier whole blood in PAXgene RNA tube samples. In 2022, Sutherland et al. for the TrENDx-TB Consortium published interim results indicating that the Cepheid MTB-HR cartridge meets the minimal target product profiles for a TB triage POCT using fingerstick blood, regardless of geographic area or HIV infection status. I hope the full results of the study will bring great news and help close the TB diagnosis gap.

With our valuable stored samples, such as whole blood in PAXgene RNA tubes from TRIPOD, and the biomarker assay training gained by Gustiani, I hope INA-RESPOND can collaborate and make significant contributions to biomarker diagnostic research in the fight against TB. I believe that setting a solid start for TB diagnosis is essential to Ending TB. In the spirit of the 2024 Olympics, with the slogan “Games Wide Open,” let’s race towards the finish line and achieve victory together!