Time-to-Tuberculosis disease diagnosis after completion of Tuberculosis preventive therapy among people living with HIV on Antiretroviral Therapy in Eastern Uganda: A retrospective cohort study

This retrospective cohort study in Eastern Uganda reveals that approximately 21.5% of HIV-positive individuals on antiretroviral therapy develop active tuberculosis shortly after completing preventive therapy, with shorter ART duration and clinically diagnosed TB identified as key predictors of early reactivation despite viral suppression.

The Gist

Imagine your immune system is a castle defending your body, and the HIV virus is a siege engine slowly weakening the walls. To help, doctors give you Antiretroviral Therapy (ART), which acts like a repair crew, fixing the walls and keeping the siege engine at bay.

But there's another enemy lurking nearby: Tuberculosis (TB). Think of TB as a silent saboteur hiding in the castle's basement. Even when the walls are being repaired, this saboteur can wake up and cause trouble.

To stop the saboteur, doctors prescribe TB Preventive Therapy (TPT). This is like sending in a special cleanup crew to sweep the basement and kick the saboteur out before they can cause damage.

The Big Question:
The researchers in this study wanted to know: Once the cleanup crew leaves, how long does it take for the saboteur to sneak back in? And more importantly, who is most likely to get caught by the saboteur again?

The Story of the Study

The team looked back at the records of 670 people living with HIV in Eastern Uganda. These were people who had already finished their "cleanup crew" (TPT) treatment but still got sick with TB later on.

They treated this like a detective story, looking for clues in the patients' files to figure out why some people got sick again very quickly (within a few years), while others stayed safe for longer.

What They Discovered (The Clues)

Here are the main findings, translated into everyday terms:

1. The Saboteur Returns Fast: Shockingly, 1 in 5 people (21.5%) got TB again very soon after finishing their preventive treatment. On average, it took about 2.6 years for the disease to show up again. It's like cleaning your house, only to find a new leak in the roof less than three years later.
2. The "Newer" Castle Walls: People who had been on their HIV repair crew (ART) for less than 5 years were much more likely to get TB again. It seems that even if the walls look okay, they might not be strong enough yet to fully keep the saboteur out.
3. The "Hidden" Saboteur: Some people got TB even though they were doing everything right—taking their meds and having their virus under control (viral suppression). This is like having a fully repaired castle but still finding a hidden trapdoor the saboteur used.
4. The Location Factor: Interestingly, people treated at one specific center (TASO Soroti) were much safer than those at the other two. It's as if that specific location had a better security guard or a more thorough cleaning protocol.

The Takeaway

The main lesson here is that one round of cleaning isn't always enough.

Even if you take your HIV meds perfectly and finish your TB prevention course, the "saboteur" can still return, especially if you haven't been on HIV treatment for very long.

What should we do?
Instead of just doing a one-time cleanup, we need to:

• Keep the lights on: Continue checking for TB regularly, not just once.
• Double-check the basement: For people who are high-risk (like those new to HIV treatment), we might need to send the cleanup crew back in for a second round.
• Learn from the best: Figure out what the "Soroti" center is doing differently and copy it everywhere.

In short: Stay vigilant. Just because the walls are being fixed doesn't mean the job is done forever; we need to keep watching for the saboteur.

Technical Summary

Technical Summary: Time-to-Tuberculosis Disease Diagnosis Post-TPT in PLHIV in Eastern Uganda

1. Problem Statement

Despite the efficacy of Tuberculosis Preventive Therapy (TPT) in reducing active TB risk among People Living with HIV (PLHIV), TB/HIV co-infection remains a critical public health challenge, persisting at rates of 40–45%. There is growing concern regarding the durability of protection provided by a single course of TPT. While PLHIV face a 12-fold higher risk of TB reactivation compared to HIV-negative individuals, the specific timeline for TB onset after TPT completion and the predictors of early reactivation in this population within the Eastern Uganda context were not well-characterized. This study addresses the gap in understanding the temporal dynamics of TB diagnosis following TPT completion and identifies risk factors for early disease recurrence.

2. Methodology

• Study Design: A retrospective case-only cohort study.
• Setting: Three TASO (The AIDS Support Organization) Centres of Excellence in Eastern Uganda: Soroti, Mbale, and Tororo.
• Data Sources: Routine data extracted from Uganda's electronic medical record (EMR) system, TB registers, and physical patient files.
• Study Period: 2022–2024.
• Population: PLHIV on Antiretroviral Therapy (ART) who were diagnosed with active TB after completing a course of TPT.
• Analytical Approach:
  • Descriptive Statistics: Summarized participant demographics and time-to-diagnosis.
  • Inferential Statistics: Logistic regression was employed to identify predictors of "early TB" (defined as TB diagnosis occurring shortly after TPT completion).
  • Variables: Included demographic data, ART duration, viral suppression status, TPT history, TB diagnostic category (bacteriologically confirmed, clinically diagnosed, extrapulmonary), and facility location.

3. Key Contributions

• Temporal Analysis: Provides specific data on the "time-to-TB" interval post-TPT completion in a resource-limited, high-burden setting (Eastern Uganda).
• Risk Stratification: Identifies specific subgroups (e.g., those with shorter ART duration and clinically diagnosed TB) that remain at high risk for early reactivation despite completing preventive therapy.
• Paradoxical Findings: Highlights the counter-intuitive association between viral suppression and early TB risk, suggesting that viral load alone may not be a sufficient proxy for TB immunity in the post-TPT period.
• Policy Relevance: Offers evidence to guide the potential need for repeat TPT or intensified continuous monitoring for high-risk PLHIV groups.

4. Key Results

• Cohort Characteristics: The study included 670 participants.
  • Demographics: Predominantly female (69.3%, n=464) with a mean age of 51.6 years (SD 14.5).
  • Treatment Context: 95.7% were on Dolutegravir-based ART regimens; 82.8% were virally suppressed.
• TB Diagnosis Breakdown:
  • Newly Diagnosed TB: 95.2% (n=638).
  • Classification: 79.9% bacteriologically confirmed pulmonary TB, 18.4% clinically diagnosed TB, and 1.8% extrapulmonary TB.
• Incidence of Early TB:
  • Prevalence: 21.5% (n=144) of the cohort developed "early TB."
  • Timing: The average time from TPT completion to TB diagnosis was 2.6 years.
• Predictors of Early TB (Multivariable Analysis):
  • Protective Factor: Care at TASO Soroti was significantly protective (Adjusted Odds Ratio [aOR] = 0.104, p < 0.001).
  • Risk Factors:
    • Clinically Diagnosed TB: Increased odds of early TB (aOR = 1.91, p = 0.007).
    • Shorter ART Duration:
      • <5 years on ART: aOR = 3.07 (p = 0.001).
      • 5–10 years on ART: aOR = 1.74 (p = 0.018).
    • Viral Suppression: Surprisingly, viral suppression was associated with higher odds of early TB (aOR = 1.87, p = 0.014), suggesting that immune reconstitution or other factors may play a complex role.

5. Significance and Implications

The study demonstrates that TB can re-emerge relatively quickly (within ~2.6 years) after TPT completion in PLHIV, with one in five patients developing early disease. This challenges the assumption that a single TPT course provides long-term immunity, particularly for those with shorter ART durations.

The findings suggest that current guidelines may need refinement for high-risk groups in Eastern Uganda. Specifically:

1. Enhanced Screening: Continuous, active TB screening is necessary even after TPT completion.
2. Repeat TPT: Consideration of repeat or extended TPT courses for patients with shorter ART duration (<10 years) or those who remain clinically vulnerable.
3. Clinical Vigilance: Clinicians should maintain a high index of suspicion for TB in virally suppressed patients, as viral suppression alone does not eliminate the risk of early reactivation.

This research provides critical evidence for optimizing TB/HIV co-management strategies in Eastern Uganda and similar high-burden settings.