Determinants of isoniazid preventive therapy among people living with HIV in Kasaï-Oriental Province, Democratic Republic of the Congo: a cross-sectional study

In many parts of sub-Saharan Africa, a silent partnership between two diseases continues to claim lives. One is HIV, a virus that weakens the body's defenses. The other is tuberculosis, a bacterial infection that attacks the lungs. When a person lives with HIV, their immune system is so compromised that a dormant tuberculosis infection can wake up and turn into active, deadly disease twenty to thirty times more easily than in someone without the virus. For decades, doctors have known a simple way to stop this from happening. By giving HIV-positive patients a specific antibiotic called isoniazid for several months, even if they do not yet have active tuberculosis, the risk of the disease developing drops significantly. This preventive treatment is a cornerstone of global health advice, yet in many places, it remains largely unused.

A recent study from the Democratic Republic of the Congo shines a light on why this life-saving medicine is not reaching the people who need it most. Researchers in the Kasaï-Oriental province, specifically in the city of Mbujimayi, looked at the medical records of nearly 1,200 adults living with HIV. They wanted to understand who was getting this preventive treatment, who was not, and what happened to those who started it. The findings reveal a stark reality: while the medicine exists and works, the system to deliver it is broken. Only about one in five eligible patients actually started the treatment, and of those who did, almost none finished the full course required to make it effective. The study identifies specific gaps in care—such as where patients live and which HIV medicines they take—that determine whether a person receives protection against tuberculosis.

The research team examined data collected between 2020 and 2022 from the main HIV care facilities in Mbujimayi. They reviewed the charts of 1,176 adults, looking at their age, where they lived, their health status, and the specific drugs they were taking for HIV. The goal was to see how many of these patients were prescribed isoniazid preventive therapy, often given alongside vitamins to protect the liver, and how many managed to stay on the medication for the full six months needed to clear the risk. The results were sobering. Out of the entire group, only 245 people, or roughly 21 percent, ever started the preventive treatment. Even more alarming was the outcome for those who did start. Of the 245 initiators, 106 stopped taking the medicine before the six-month mark. In the end, only two patients out of the entire 1,176-person group had a documented record of completing the full course. This near-total failure to finish the treatment means that the vast majority of patients who began the process received almost no long-term protection.

The study went further to find out what factors made a difference in whether a patient started the treatment. The researchers found that four specific things were strongly linked to getting the medicine. First, where a person lived mattered greatly. Patients living in the city were far more likely to start the treatment than those in rural areas. Second, the type of HIV medication a patient was taking played a huge role. Those on a modern, three-drug combination regimen were much more likely to receive preventive therapy than those on older drug combinations. Third, the severity of the patient's HIV infection at the time they entered the program mattered; those who were healthier and in earlier stages of the disease were more likely to get the treatment than those who were already very sick. Finally, simply staying active in the HIV care program doubled the chances of receiving the preventive medicine. Patients who kept coming to their appointments had more opportunities to be screened and prescribed the treatment.

These findings point to a system where access to care is uneven and where the process of delivering preventive treatment is fragile. The researchers suggest that the low completion rate is likely due to a combination of factors, including frequent shortages of the necessary medicines and vitamins, a lack of clear tracking systems to follow patients, and the high number of people who drop out of care entirely. The fact that patients on newer HIV drugs were more likely to get the treatment suggests that the introduction of these new drugs coincided with a period of better training or stronger support for preventive care, but that this benefit has not spread to everyone. The study concludes that to fix this, health programs need to secure a steady supply of the medicines, train healthcare workers to prescribe them confidently, and find better ways to keep patients engaged in their care. Without these changes, the promise of preventing tuberculosis among people living with HIV will remain unfulfilled in this region, leaving thousands vulnerable to a disease that could have been stopped.