1. Introduction
The provision of antiretroviral therapy (ART) to HIV-infected individuals has saved millions of lives in resource-limited settings since HIV has remained a health global concern [
1,
2]. Globally in 2022, 39.0 million were living with HIV, 1.3 million people became newly infected with HIV, and 630,000 people died from AIDS-related illnesses [
3]. The use of ART has led to low levels of morbidity and mortality, immunological recovery and reduction of the viral load [
4,
5,
6,
7]. Immunological recovery or CD4 count recovery is when the patient’s CD4 count has reached more than 500 cells/
. About 15–20% of patients who initiate ART with very low CD4 counts (200 cells/
) may continue to have abnormally low CD4 cell counts and have the highest risk of failure to achieve optimal immunological recovery [
8,
9]. Patients on ART with poor CD4 recovery early in treatment are at greater risk of progression to new AIDS diagnosis or death despite viral suppression. CD4 cell counts remain low among individuals presenting for care in many areas [
10] and up to 17% of adults die in sub-Saharan Africa in the first year after ART initiation [
11]. Consequently, in developing countries, high mortality rates persist despite the availability of antiretroviral and AIDS-defining events that continue to be reported as the main cause of hospitalization and death [
12,
13,
14,
15,
16]. Risk factors for death in the initial year after starting ART have been linked to a low CD4 count <50 cells/
conferring particularly high risk [
17]. In some cases, drug resistance may also cause an abnormally low CD4 count. Individuals with drug-resistant strains of HIV may experience treatment failure, leading to disease progression and an increased risk of mortality.Patients with advanced-stage disease for example WHO clinical stage 3 or 4 may have a higher risk of mortality before CD4 count recovery due to more severe illness and opportunistic infections [
18]. Rapid disease progression or delayed diagnosis in patients may have more extensive immune damage, making them more susceptible to complications and death before CD4 count recovery [
19].
Recent studies researched different competing events associated with patients on ART. Yang et al. (2021) researched on competing risks of CD4 count and AIDS-related mortality. The results showed that low CD4 was associated with higher AIDS-related mortality. Patients with CD4 count
500 cells/
at baseline had lower AIDS-related mortality [
20]. Progression rates for AIDS and non-AIDS are significantly the same. However, patients who initiate ART with a CD4 count
200 cells/
are at risk even after CD4 count recovery [
21]. There is also a high risk of loss to follow-up and mortality in patients with low baseline CD4 count [
22,
23]. Patients with high CD4 counts who initiate ART late had a higher risk of AIDS-related death than those with low CD4 counts who start ART early [
24]. Our research objective was to find the determinants of death before CD4 count recovery in the presence of competing events. Out of the patients who had not reached a CD4 count of at least 500 cells/
, death precluded the occurrence of CD4 count recovery, hence competing risk models were implemented. Therefore, this study implores competing risk analysis techniques to determine the time taken to CD4 count recovery as well as to identify the determinants of death before CD4 count recovery for people living with HIV/AIDS infection under ART in KwaZulu-Natal, South Africa.
4. Discussion
This study used competing risk models to determine factors that contribute to the death of patients who were initiated on antiretroviral before reaching a CD4 count of at least 500 cells/
, those who did not experience CD4 count recovery and those who recovered their CD4 count. Patients with no tuberculosis had a higher risk of mortality compared to the prevalent tuberculosis. The results reaffirm the results found by other authors [
28,
29]. Prevalent tuberculosis showed a low risk of mortality because they are initiated early in ART, and co-infections like tuberculosis are identified at an early stage. Immunological restoration through antiretroviral reduces morbidity and mortality in prevalent tuberculosis patients [
30]. HIV patients with low CD4 counts are at high risk of developing tuberculosis compared to individuals without HIV infection. If the level CD4 count of is low, the ability of the immune system’s ability to fight against infections is compromised leading to individuals being susceptible and transit from HIV to AIDS [
31,
32]. The cumulative incidence of patients with prevalent tuberculosis was lower than those with tuberculosis in patients with recovered CD4 count. Effective tuberculosis treatment helps cure the infection leading to the reduction of tuberculosis reactivation or acquiring new tuberculosis infections. Prevalent tuberculosis patients had a low risk of developing active tuberculosis compared to those without tuberculosis, since the immune system regained strength and can effectively control tuberculosis infections [
33].
Rural patients showed an elevated risk of mortality before recovery of CD4 count than their urban counterparts. Rural areas have inferior health facilities, limited resources and medication [
34,
35]. Patients walk long distances to get medical assistance, poor background presentation and low levels of literacy lead to high rural mortality [
36]. Patients in urban access their HIV medication conveniently, since there are many health facilities at their disposal. Rural patients had an increased cumulative incidence than urban patients who had recovered their CD4 count [
37]. The contributing factors are socioeconomic factors, environmental factors and social support networks. Rural patients with HIV may face challenges in terms of social support networks caused by isolation, stigma, and limited access to support groups or networks can impact mental health, treatment adherence, and overall well-being, potentially influencing cumulative incidence rates [
38]. Rural areas may have higher levels of poverty, limited education, and fewer economic opportunities compared to urban areas [
39]. These socioeconomic factors can influence health-seeking behavior, adherence to treatment, and overall health outcomes, which may contribute to variations in cumulative incidence. Rural areas may have different environmental conditions that can impact health outcomes. For example, exposure to agricultural chemicals, limited access to clean water and sanitation, or increased prevalence of certain co-infections can contribute to the increased risk of specific outcomes in rural patients with HIV. The availability of comprehensive HIV care, early diagnosis, consistent access to ART, and ongoing monitoring are crucial for reducing the burden of HIV-related outcomes in both rural and urban settings [
40]. Availability of comprehensive HIV care, early diagnosis, consistent access to ART, and ongoing monitoring are crucial for reducing the burden of HIV-related outcomes in both rural and urban settings [
41,
42].
Females experienced a lower cumulative incidence than males, when they had not recovered their CD4 count. The causes of the disparities are behavioral, access to health care and treatment, social and cultural factors. Differences in sexual behavior and risk-taking practices can influence the cumulative incidence of HIV-related outcomes. Males may engage in higher-risk sexual behaviors, such as having multiple sexual partners or engaging in unprotected sex, which can increase their risk of HIV acquisition and disease progression [
43]. Females may have better access to health care services, including HIV testing, prevention measures, and treatment, which can contribute to lower cumulative incidence rates. Factors such as antenatal care utilization, which provides opportunities for HIV testing and prevention interventions, can play a role in reducing HIV incidence among females [
44]. Gender norms, power dynamics, and societal expectations can influence HIV risk and outcomes. Cultural practices or norms that promote male dominance or discourage female empowerment can contribute to increased HIV risk for males [
45]. Comprehensive HIV prevention strategies, access to testing, treatment, and addressing gender-specific barriers are crucial for reducing the burden of HIV-related outcomes in both males and females. Co-infections and comorbidities may be experienced in females when the cumulative incidence increases in females than males after CD4 count recovery. Sexually transmitted infections or gynecological conditions may be more prevalent in females and can impact HIV progression or the development of specific complications [
46]. The results from the study showed that males had an increased cumulative incidence of mortality before CD4 count recovery compared to females. The results are supported by other authors who stated that males had higher patient attrition and mortality compared to females and this may be attributed in part to late presentation for HIV treatment and care [
47,
48].
Patients on first-line had higher chances of experiencing death compared to the ones on second-line. Reports from other authors showed that patients who took too long to switch to the second-line medication due to drug resistance, virological failure, and rapid CD4 count decline had a high risk of dying [
49] and transmitting the HIV virus to uninfected sex partners [
50,
51,
52]. Our results showed that patients with low viral load significantly had lower chances of death compared to those with higher viral load. The HIV viral load was considered a standard marker for the evaluation of treatment success and to detection virological failure. WHO defined virological failure as two consecutive viral loads of more than 1000 copies /ml after 6 or more months [
53,
54]. At ART initiation, the median CD4 count was 109 with an inter-quartile range of 52-154 for patients who recovered their CD4 count. Patients with baseline CD4 cell counts of less than 50 cells/mm3 have a greater chance of immunological recovery compared to those with higher CD4 counts. Consequently, their CD4 counts remain below 200 cells/
for a greater period leading to an increment in morbidity and mortality [
55]. Several studies showed that baseline CD4 count is associated with immune reconstitution [
56,
57]. Immune reconstitution is not entirely determined by the baseline CD4 count but is also influenced by factors such as treatment adherence, duration of HIV infection, presence of comorbidities, age, and overall health status [
58]. Monitoring CD4 counts and assessing immune reconstitution is an essential part of HIV care. Regular monitoring allows healthcare providers to evaluate the effectiveness of ART, assess the individual's immune status, and make appropriate adjustments or modifications to the treatment regimen if necessary [
59].