Factors associated with late HIV diagnosis among adults living with HIV in Oman: a 32-year ambidirectional cohort study at a tertiary referral hospital

BACKGROUND: Despite advances in the management of Human Immunodeficiency Virus (HIV), delayed diagnosis remains a major public health challenge. Evidence on late HIV diagnosis in Oman and the wider Gulf region remains limited. This study aimed to identify factors associated with late HIV diagnosis among adult patients of people living with HIV (PLWH) in Oman. METHODS: A 32-year ambidirectional cohort study was conducted at the Royal Hospital, a tertiary referral hospital and the national HIV referral centre in Muscat, Oman, including adults aged ≥ 18 years diagnosed with HIV between 1992 and 2024. Participants with available baseline Cluster of Differentiation 4 (CD4) count, viral load, and haemoglobin measurements were included. Late diagnosis was defined as a CD4 count ≤ 350 cells/mm³ at diagnosis. Data were extracted from electronic medical records and analysed using multivariable Poisson regression with robust variance. Adjusted relative risks (aRRs) with 95% confidence intervals (CIs) were reported. RESULTS: Among 549 patients, 30.1% were diagnosed late. Of those diagnosed late, 72.1% acquired HIV through sexual transmission, 64.8% were asymptomatic at presentation, and 61.8% had no comorbidities. Younger age was independently associated with higher risk of late diagnosis among individuals aged 18-27 years (aRR 5.66; 95% CI: 2.26-14.21), 28-37 years (aRR 3.25; 95% CI: 1.33-7.94), and 38-47 years (aRR 3.51; 95% CI: 1.40-8.77), compared with those aged > 47 years. Low haemoglobin (≤ 10 g/dL) was associated with increased risk (aRR 3.03; 95% CI: 1.42-6.67). Heart disease (aRR 5.38; 95% CI: 1.36-21.31) and hypertension (aRR 3.34; 95% CI: 1.13-9.91) were also significant predictors. Sex, mode of HIV transmission, and reason for HIV testing were not significantly associated with late HIV diagnosis in the adjusted analysis. WHO clinical stage 2 was also not significantly associated. CONCLUSION: Late HIV diagnosis remains common in Oman and is associated with younger age, anaemia, and comorbidities. These findings highlight missed opportunities for earlier HIV testing, as a substantial proportion of late-diagnosed individuals were asymptomatic and many were young adults. Strengthening targeted testing strategies, reducing stigma, and improving early linkage to care are essential to support timely diagnosis and progress toward the UNAIDS 95-95-95 targets.