Introduction

Worldwide, tuberculosis (TB) is considered the leading cause of premature death among HIV/AIDS patients1,2. Tuberculosis is caused by Mycobacterium tuberculosis and mainly affects the lungs but it can also affect other body parts such as the brain, kidneys, or spine. HIV coinfection is the prime risk factor for developing active TB in the high-burden settings. This in turn increases the susceptibility to primary infection or reinfection and the risk of TB reactivation for patients with latent TB1,3. Mycobacterium tuberculosis also has a negative effect on the immune response to HIV, accelerating the progression from HIV infections to AIDS4. Furthermore, the risk of developing TB among people living with HIV (PLHIVs) is 18 times higher than the general population5.

According to WHO, up to 10.6 million people were estimated to be affected with TB worldwide in 2021, with up to 1.6 million TB deaths recorded including 187,000 HIV-positive people2. According to the report, Sub-Saharan Africa in 2017 was home to 70% of all people living with HIV/TB co-infection in the world. Uganda is among the 30 high TB burden countries and these countries accounted for 87% of new TB cases2.

The WHO recommends Isoniazid preventive therapy, intensified case finding and infection control (three ‘I’s) as the main strategies in the prevention of TB among people living with HIV6.

Studies have shown that IPT can significantly lower TB incidence among PLHIV after completion of the 6 month period of treatment7. However, uptake of IPT has been relatively low in most developing countries including Uganda2,8.

Information on enrolment, retention, challenges faced, loss to follow up, completion and prevalence of TB during the treatment period has been documented5,9,10. However, there are hardly any studies documenting prevalence of TB among PLHIV who have completed IPT therapy and its associated predisposing factors, hence the study.

Methods

Study design

A cross sectional study was conducted among PLHIV above 18 years who completed Isoniazid preventive therapy and had their clinic appointments between July and September, 2022. The study was carried out at Reach out Mbuya community health initiative in Nakawa division, Kampala district, central Uganda. Reach out Mbuya is a community-based non-governmental organization providing a unique model of care to PLHIV and where necessary their families; taking care of the medical, social, emotional and economical aspect of their lives to foster dignified living. The organisation started with 14 HIV positive clients in 2001, and currently serves ≥ 7000 annually.

Eligibility criteria

All the people living with HIV/AIDS above 18 years, on Antiretroviral treatment (ART), TB disease negative, with documented records of Isoniazid preventive therapy completion and had consented were included in the study.

All potential participants with comorbidities that could compromise with their immunity, those who experienced side effects while on ART, and those patients who did not complete treatment due to personal or medical reasons were excluded from the study.

Sample size estimation and sampling procedure

The sample used in the study was estimated using the formula for sample size calculation for a known population as follows11;

$$ {\text{n}} = \frac{1}{{\left( {1/{\text{n}}_{0} + 1/{\text{N}}} \right)}} $$

where,

$$ {\text{n}}_{0} = \frac{{{\text{Z}}^{2} {\text{P}}\left( {1 - {\text{P}}} \right)}}{{{\text{D}}^{2} }} $$

Sample prevalence (P) of 7.2% from a previous study in Uganda done by Moore et al.12, a margin of error (5%), (D = 0.05) and 95% level of confidence (Z = 1.96) and a known population (N) of 1000 patients were used to calculate sample size of 93 participants. To increase precision of the study, a total of 103 participants was selected using simple random sampling technique from a list of all patients who had completed IPT and had their clinic appointments in the July–September quarter, 2022.

Data collection

A questionnaire was entered in Kobocollect toolbox software and used to capture participants’ demographic data and data assessing potential predisposing factors for TB in people living with HIV/AIDS. Such factors included; patient smoking, ability to disclose their HIV status, having awareness of isoniazid therapy as a preventive measure against TB, experienced side effects during isoniazid treatment period (allergic reactions, drowsiness), considered taking ART and isoniazid therapy burdensome (with regards to different types and quantities of pills to be taken), experienced stigma when observed by public that they were on treatment and whether they attended counselling sessions. The patients were asked to produce sputum samples into a clean, sterile, leak proof and labelled sputum cup for gene xpert test. Those who were not able to produce the sputum were requested to provide urine in a leak proof, screw capped labelled urine sample container.

Analysis of samples

Gene Xpert

The sputum samples were tested using Gene Xpert test to detect presence of Mycobaterium Tuberculosis with a Cepheid machine developed by Cepheid International13. The test is a cartridge based nucleic acid amplification rapid test, highly sensitive and specific for Mycobacterium tuberculosis as well as Rifampicin resistance detection14.

Lateral flow urine lipoarabinomannan (LF-LAM) assay

The urine samples from the people who were not able to produce sputum were tested using a lateral flow urine lipoarabinomannan (LF-LAM) commonly known as urine LAM. The test which was developed by WHO employs highly purified antibodies specific for the major polysaccharide antigen of the Genus Mycobacterium in urine15.

Data analysis

The data collected using Kobo toolbox was extracted, cleaned in Microsoft excel and analysed using STATA (version 14) statistical package. Logistic regression analysis was performed to determine the relationship between potential predisposing factors and prevalence of TB among HIV patients.

Ethics approval and consent to participate

This study was approved by Mulago Hospital Research Ethics Committee (protocol MHREC 2370). Informed consent was obtained from all subjects and/or their legal guardian(s) before their participation in the study. Participants' details were kept confidential by using special data codes. All methods were performed in accordance with the relevant guidelines and regulations of the journal.

Results

Socio-demographics of the participants

A total of 103 PLHIV were included in the study. Majority of the participants were female 62 (60.2%). The mean age of the participants was 42.1 (SD = 10.5) and median age was 43 (IQR = 16). Most of the participants 54 (52.43%) were urban dwellers, with up to 37 (35.7%) having attained secondary level of education. Up to 58 (56.3%) participants were married, 59 (57.3%) were employed and 33(33.0%) were Catholics. Details are shown in Table 1.

Table 1 Frequency distribution of social-demographic characteristics.
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Prevalence of tuberculosis

The overall prevalence of TB among the study participants was 5.8%. Out of the 65 patients tested by Gene Xpert, only 3 (4.6%) were TB positive, while out of 38 patients tested by TF-LAM, 3 (7.9%) were positive as shown in Table 2.

Table 2 Prevalence of tuberculosis.
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Predisposing factors of TB in PLHIV who completed IPT

Bivariate and multivariate logistic regression were performed to assess the association between TB prevalence (dependent variable) and various predisposing factors (independent variables).

Bivariate analysis showed that being married (living with a partner) (OR = 0.171, P = 0.014) and receiving counselling (OR = 0.013, P = 0.001) had a relationship with TB prevalence among HIV patients (Table 3).

Table 3 Bivariate logistic regression of predisposing factors with TB in HIV patients.
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Factors with P-values ≤ 0.1 such as marital status, employment and adherence to counselling were included in a model for multivariate logistic stepwise regression analysis. It was observed that only counselling was the only significant factor associated with prevalence of TB in HIV patients (aOR:0.028, P-value < 0.001, 95% CI 0.0041–0.1924) (Table 4).

Table 4 Multivariate logistic regression of predisposing factors with TB in HIV patients.
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Discussion

Tuberculosis continues to be the leading cause of mortality among PLHIVs in Sub-saharan Africa including Uganda. The risk of developing TB among people living with HIV (PLHIVs) is higher than the general population5. Therefore, WHO strongly recommends the use of Isoniazid preventive therapy to TB among PLHIVs to fight TB incidences in addition to infection control and active case finding16.

A number of studies have reported that IPT significantly reduces incidence of TB among PLHIV after completion of the 6 month period of treatment17,18,19. This study recorded a TB prevalence of 5.8% among PLHIV who had completed the 6 months period of IPT treatment, which is lower than 8.1% and 9.0% reported respectively in studies conducted in Ethiopia13,14. This difference might be attributed to the different study design and sampling techniques used. Other studies reported similar findings of lower incidence rates among PLHIV that completed IPT therapy than those who were not IPT therapy17,18,19.

The study observed that females had higher completion rates of IPT as compared to their male counterparts. This is in agreement with a study in Butebo, Uganda which reported that females had a higher uptake of IPT (66%) as compared to males (33.8%) in 20218.

Although TB disease was higher in males (9.8%) than in females (3.2%) in this study, gender was not an important predictor of TB disease prevalence as similarly reported in previous studies8,16.

It was observed in this study that adherence to counselling was an important predictor that reduced the likelihood of TB disease occurence. This concurs with previous studies in Ethiopia and Uganda that pre-counselling of HIV clients prior to enrolment of IPT significantly improved IPT uptake and completion hence preventing active TB20.

Although this study provides baseline evidence regarding prevalence and predisposing factors of active TB among PLHIV on IPT, the findings can not be used to affirm that administration of IPT to PLHIV effectively reduced occurrence of TB. This is because a control group of PLHIV who had not completed IPT was not included for comparative analysis. The prevalence of active TB before and after IPT was also not determined.

Conclusion

The study observed a considerably low prevalence of TB among PLHIV that had undergone IPT.

Counselling was noted to be a significant predictor of prevention of active TB among HIV patients. Therefore, in addition to the recommended 3Is, consistent counselling (pre and during treatment) should be emphasized in ensuring effectiveness of the IPT among PLHIV (Supplementary Information).