The forgotten form of TB that can carry on forever
Just like with Covid, there’s a long version of TB. The condition, called post-TB lung disease, can emerge even after people with TB have finished their courses of treatment
A dismayed patient once told me: “No one said that TB [tuberculosis] would never leave me.”
Over the course of my 13-year career as a lung specialist, I’ve had to be the one to tell dozens of shocked patients exactly this: finishing a course of TB treatment doesn’t necessarily mean they’re rid of the disease or the damage it has caused for good.
The problem is not that patients don’t respond to TB treatment — rather, they may complete their course of medicine and even feel better. But some will be stuck with a cough, or will struggle to breathe easily, which eventually gets them back to the clinic.
Our current estimates are that between 20% and 30% of TB survivors end up with some form of lung problem that makes it difficult for them to breathe. Post-TB lung disease (PTLD) develops because of the fight between the bacterium in the lower airways and the body’s response. In the process, the airways become damaged and lung tissue and its many small blood vessels get scarred and pulled out of shape.
As a result, the person may have a cough that won’t go away, feel tired or short of breath or lose weight. People who experience these symptoms also report having a lower quality of life, because it means they may not be able to do physical work or participate in sports or the other leisure activities they previously enjoyed.
Think of it as the TB version of long Covid.
Yet long Covid has received much more attention than the long shadow of TB, even though the bacterium that causes TB was identified 140 years ago. By my count, almost four times as many papers have been published about long Covid in the past three years than have ever been written about persistent lung disease after TB.
The research gaps become even worse because TB treatment programmes stop routinely paying attention to patients as soon as lab tests show that their six-month- long treatment has killed enough of the bug to prevent them from spreading it to someone else.
If we don’t change our approach to understanding the bigger picture of TB as a disease, many people will never get the help they need to lead life as they knew it after completing their initial treatment.
Because PTLD falls somewhere between an infectious disease and a chronic condition, there’s little funding for research.
As a step in the right direction, an international group of lung experts have included PTLD in their action plan for 2020 to 2025 to help TB survivors. The document was drawn up after a scientific meeting hosted at Stellenbosch University and supported by the International Union against Tuberculosis and Lung Disease.
Why should you care? Here are three reasons.
- TB doesn’t go away — nor does its fallout
In South Africa alone, more than 300,000 people will be living with tuberculosis this year. Approximately 20% of TB survivors will have some kind of damage to their lungs and almost a quarter will have mental health problems, including depression and anxiety.
These numbers are higher still in poorer communities, where people can’t get to a clinic or doctor fast, and the social and economic impact of TB therefore becomes more devastating. It is now believed that almost half of all disability attributed to the disease occurs after patients have completed their treatment.
Moreover, TB survivors are much more likely to get infected again than people who have never had the disease, which makes the long-term physical, psychological and economic effects worse. With each successive bout of TB the likelihood for someone to return to work drops, feeding the cycle of despair.
On top of that, surviving TB increases someone’s risk of dying prematurely almost threefold compared with people who’ve not had TB. What is less clear is what the cause of this premature death is.
- Spotting PTLD has to become easier, cheaper and more accurate
There are three ways to detect PTLD, though it’s not clear which method works best.
One way is to do a chest X-ray or (if the patient can afford it) a computed tomography (CT) scan (a sophisticated technique that takes many X-ray images of the body from different angles and then puts them together to create a single picture) so that a doctor can see what TB damage lurks in a patient’s lungs.
But imaging facilities are not available at all South Africa’s state facilities — and even when they are, getting a slot is difficult because the equipment is used for many other patients too.
A more common way is to test how big someone’s lungs are by using a spirometer. In this test, a patient breathes in as deeply as they can and then has to try to empty their lungs as best they can. The doctor then compares the volumes of air that were inhaled and exhaled against what healthy lung function would look like.
However, if a health worker isn’t properly trained in doing the test or if the instrument isn’t set up correctly, results won’t be accurate. A bigger problem, though, is that it’s not always easy to interpret results. Abnormal results could mean that a TB patient may have long-lasting lung damage — but sometimes a patient has trouble breathing even when spirometry results show, on paper, that the patient’s lung function is good enough. We need to understand the link between test results and actual lung function better.
3. TB patients need more than antibiotics
People who experience the debilitating, and sometimes deadly, aftershock of TB need to have their battles acknowledged — if we don’t acknowledge them, the psychological impact of the condition will become more difficult to deal with.
TB survivors and affected communities need to feel comfortable to stand up and tell their stories. In the case of long Covid, we’ve seen how powerful these personal accounts can be to drive investment and innovation.
That means that doctors and nurses should be trained to be equipped to identify when people are struggling with the fallout of TB even if they test negative after treatment.
Also, South Africa’s TB programme should keep monitoring people who’ve finished taking their antibiotics so that health workers can catch any damage that could affect people’s quality of life.
This further means that the health professionals a patient may encounter outside their usual treatment team at a clinic (for instance, a nurse or a junior doctor) must know how to identify and treat PTLD.
Researchers are uncertain about how long TB survivors should be monitored, because there’s little information about when somebody is in the clear.
At the very least, protecting and preserving people’s lungs should be the main priority of South Africa’s TB project — not just producing negative TB tests.
But this goal has been omitted from all TB research to date. We need to change that.
Brian Allwood is an associate professor in the division of pulmonology at Stellenbosch University and Tygerberg Hospital. His PhD evaluated the link between TB and the subsequent development of chronic obstructive pulmonary disease.
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