An estimated 37.7 million people were living with HIV (PLWHIV) at the end of 2020, over two-thirds of whom are in the African Region [1] . In Cameroon, about 3.7% of the adult population is HIV positive [2] . HIV continues to be a leading cause of illness and death worldwide, with about 690,000 HIV/AIDS-related deaths, of which about 440,000 (63.76%) come from Africa [3] [4] . It’s known to be the leading cause of death in Cameroon [5] .

The global expansion of access to anti-retroviral therapy (ART) over the past decade has led to substantial declines in HIV-related morbidity and mortality [5] [6] , especially in developing countries in which HIV prevalence is highest [7] . Increased access to ART is estimated to have averted more than 4 million HIV-related deaths in developing countries between 2002 and 2012 [1] . There is no cure for HIV infection [1] [8] [9] . Nonetheless, with increasing access to effective HIV prevention, diagnosis, and treatment, including opportunistic infections (OIs), HIV infection has become a manageable chronic health condition, enabling PLWHIV to lead long and healthy lives [1] [7] [10] . The incidence of OI has then decreased, and mortality associated with HIV has improved dramatically [11] [12] .

HIV care and treatment were expected to improve in Cameroon as free ART has been available since 2007 [13] . The WHO recommended the HIV test and treat (T&T) strategy since 2015 as a global approach to control the pandemic [13] [14] . The approach aims at increasing ART coverage, to attain community viral load suppression by testing everyone for HIV, placing those who test positive on ART irrespective of their CD4 count or clinical criteria, and maintaining HIV positive people on ART to achieve sustained viral load suppression [15] - [17] . The overall goal of the universal test and treat (T&T) strategy is to end the AIDS epidemic as a public health threat by 2030 [13] . With the ambition to achieve ART coverage as well as to reach the global objective of eliminating HIV by 2030, the Cameroon Ministry of Public Health, in May 2016, implemented the WHO HIV T&T strategy in all health facilities providing HIV services within the national territory [13] .

With the access and scale-up in the provision of ART in PLWHIV worldwide, the reasons for their admission and hospitalisation outcome could have changed. A systematic review conducted in 2015 has summarized data on causes of hospital admission among PLWHIV globally. AIDS-related illnesses and bacterial infections were the second most common causes of adult HIV admissions in all geographical regions and the most common causes of hospital death [7] . Studies in other regions, mostly in developed countries, have shown changes in the main causes of admission and death of PLWHIV; OIs have given way to chronic diseases and neoplasms not associated with AIDS [7] [10] . There is substantial literature available on HIV/AIDS in SSA and Cameroon, but there is limited information about the causes of hospitalisation and outcomes of PLWHIV in the South-West region. We therefore aimed at identifying the causes of admission, determining the in-hospital outcome, and identifying factors associated with poor outcome in PLWHIV in a tertiary-level hospital in Cameroon.

Out of the 10328 files screened, 982 files met the inclusion criterion; the proportion of admissions of PLWHIV in BRH during the study period was 9.5%. 92 files were excluded, giving a final sample size of 890 files. See Figure 1 below.

The hospitalisation rate of PLWHIV in the BRH was high (9.5%), and the top 5 leading causes of admission were Tuberculosis (16.1%), pneumonia (13.4%), renal failure (13.1%), diarrheal diseases (11.3%), and meningoencephalitis (10.5%). The overall proportion of communicable diseases was much higher than that of non-communicable diseases (70% versus 30%). In-hospital mortality was high (26.1%), with the predictor of mortality being the absence of cotrimoxazole prophylaxis on admission.

Communicable diseases are still the leading causes of admission in patients with HIV. This is similar to the findings obtained in most studies in SSA, where most of the hospital admissions were from Opportunistic Infections such as Tuberculosis [16] - [23] . This group of diseases are endemic in the general population, and this could explain their higher prevalence in our patients. A systematic review and meta-analysis conducted in 2015 by Ford et al have summarized data on causes of hospital admission among children and adults living with HIV globally where they identified that AIDS-related infections (particularly tuberculosis) and bacterial infections (particularly pneumonia) continue to be the leading causes of hospital admission in adults and children living with HIV worldwide [7] . These findings are contrary to what is reported in high-income countries, where opportunistic diseases have given way to chronic diseases and neoplasms not associated with AIDS [7] [10] [24] [25] . However, we should note here that non-communicable diseases represented 30%. This proportion has increased when compared with the ones recorded in similar studies done a couple of years ago in Ethiopia (22.7%) [26] and Nigeria (21.3%) [16] , marking the epidemiological chance of transition from communicable to non-communicable diseases in PLWHIV.

In contrast with other similar studies done in SSA [16] [27] , the proportion of renal failure as a cause of admission was quite significant, ranked as the third leading cause of admission in our study. This finding could be explained by the presence of other risk factors of renal failure in those patients, the ART toxicity to the kidneys and the fact that the BRH has one of the nine national dialysis centres in Cameroon, the only one in the South-West Region, where patient with renal diseases converge from the entire region and out [28] .

Most of the patients (81.5%) in this study were found to be in the advanced WHO clinical stage (stage 3 - 4), which could explain the majority of the causes of admission. This picture was also observed in similar studies conducted in Uganda (85%) [27] , Ethiopia (82.2%) [26] , West Africa (94%) [29] , and in China (74.8%) [30] . In addition, it’s known that the risk of admission is high amongst patients who were not on cotrimoxazole upon admission [22] . Close to 40% of patients with a previous diagnosis of HIV positive in our study were not on cotrimoxazole.

Out of the 890 recruited files, 640 (71.9%) patients were discharged and 18 (2%) were transferred; this proportion of transferred patients was similar to a study done by Long et al. [21] but lower compared to the one done by Mishore et al. (4%) [26] . This could be explained by the fact that the BRH has a national dialysis centre, there are a good number of specialists in various fields, and pathology can be done in situ; all of this reduces the chances of referral. 232 patients died during hospitalisation, especially within the first week (60.8%), giving a mortality rate of 26.1%. This mortality was almost similar to a previous study conducted in Cameroon by Luma et al. (23.6%) [31] but lower in similar studies in SSA, where it ranged from 28.7% to 40.6% [16] [17] [20] [23] [29] [32] [33] . In a worldwide systematic review and meta-analysis, in-hospital mortality among adults living with HIV was 20% overall, but highest in the African region with 31% [7] . Our finding was much higher than the one in similar studies conducted in higher-income countries such as France (5%), China (8.7%), Spain (13.5%), and South Africa 17% [21] [30] [34] [35] . The high mortality observed in this study is probably because of the advanced disease and HIV stage at presentation, the presence of opportunistic infections, and the lack of resources for care [25] [29] [33] [36] . Other considerations could include late diagnosis, late presentation to HIV care, and low ART uptake, which are related to poor outcomes [37] - [41] . In our study, 77.1% of admitted patients had a known diagnosis of HIV, and more than half of the patients (51.9%) were not on ART or not compliant. A significant proportion of patients get diagnosed HIV positive during admission or die with a recent diagnosis [29] [42] .

As far as the duration of hospitalisation is concerned, we found that the majority (57.9%) had a prolonged hospital stay (≥ 7 days). This finding was in accordance with Mishore et al. [26] . Non-adherence to the ART regimen was found to increase the risk and duration of hospitalisation in PLWHIV [43] [44] . Less than half (48.1%) of patients in this study said to be adherent to ART upon admission, which could explain our finding.

In this study, renal failure was found to be the leading (17.7%) cause of death in contrast to what was reported in previous studies done in Cameroon (3.4%), Uganda (4%), and Nigeria (7.4%) [16] [27] [31] . As said earlier, our finding could be explained by the presence of other risk factors for renal failure, the ART toxicity to the kidney and the fact that the BRH has the only dialysis centre in the South-West Region of Cameroon.

Meningoencephalitis (including bacterial, aseptic, toxoplasmosis, and cryptococcosis) had a significant proportion (17.2%) of deaths. This proportion was almost similar to a study conducted 2 years ago in Nigeria (17.8%) [16] , but lower than the one conducted 4 years ago in Cameroon by Luma et al. (23.4%) [31] . Our finding shows a considerable improvement in mortality due to meningoencephalitis in our setting, and could be explained by the efficacy of the T&T strategy recommended by WHO in 2015 and implemented in Cameroon in December 2016 [13] [14] [45] .

Although TB (13.1%) came in the third position in our study compared to other SSA studies where it was known to be the leading cause of mortality in PLWHIV [16] [17] [20] [23] [29] [39] [46] [47] , TB is still a preventable leading cause of death in PLWHIV in our setting. TB is endemic in Cameroon, and HIV infection is the strongest risk factor for developing tuberculosis [23] [48] . Furthermore, the association between HIV and TB leads to increased mortality, reinfection, and the emergence of resistant strains, as well as greater difficulties in diagnosing sputum-negative cases and extra-pulmonary TB [49] .

On multivariate analysis (table XIV), not being on cotrimoxazole prophylaxis was found to be an independent predictor of mortality, with the majority (60.8%) of deaths being during the first week of admission. These were previously described in similar studies [16] [23] [26] [31] [33] [50] . These findings can be explained by the fact that patients coming at a late stage of the disease with poor performance status upon admission died a few days after admission due to the severity of their ailment [16] . Also, Cotrimoxazole prophylaxis significantly reduces mortality in HIV-infected adults on ART [50] [51] . On the other hand, our study showed that not having an associated diagnosis, being at WHO clinical stage 1-2, and not being previously admitted were found to be protective factors against death. Multiple diagnoses predict a poor outcome in HIV/AIDS [31] [52] . Previous studies also reported that being at WHO clinical stage 3-4 was a risk factor for in-hospital mortality [23] [30] . Patients with no comorbidity on admission were more likely to stay longer in the hospital than those with at least 02 comorbidities. This was probably because those patients with at least 2 comorbidities died much earlier. We saw in this study that patients who had at least two comorbidities had a lower probability of being alive at discharge.

This was a retrospective review of patient records and thus prone to missing data such as white blood cell count, Haemoglobin level, CD4 count and viral load. Therefore, we did not finally assess other important paraclinical predictors of poor outcomes, such as viral load or CD4 counts, because they were absent. We also had some selection biases: given that our study was done in a single hospital, patients admitted to the hospital may not be representative of all admitted patients in the community and may not also be a true reflection of in-hospital mortality in the general population.

We, therefore, conclude at the end of this study that communicable diseases (including Opportunistic Infections) are still the major causes of admission among PLWHIV at the BRH, but non-communicable diseases are on the rise. The top 5 leading causes of admission were tuberculosis, pneumonia, renal failure, diarrheal disease, and meningoencephalitis in decreasing order of frequency. The in-hospital mortality was high, as more than one out of four patients died. Patients who were not on Cotrimoxazole prophylaxis upon admission were two times more at risk of dying during hospitalisation than those who were on Cotrimoxazole. We hope that our findings will help guide health policies aimed at reducing the admission rate and improving in-hospital outcomes in HIV/AIDS.

Written and informed consent was obtained for the study.

The study team would like to thank the BRH staff for their support in facilitating this study.