This is an implementation study evaluating differentiated service delivery model for the care of comorbidities for people living with HIV (PLWH). The Hybrid Type 3 study design is adopted, with the primary goal of evaluating implementation outcomes, and secondary goals of evaluating service and client outcomes according to the Reach, Effectiveness, Adoption, Implementation and Maintenance (RE-AIM) framework, including Proctor's Conceptual Framework for Implementation Outcomes, using mixed methods for data collection and analyses. PLWH will be identified from the Integrated Treatment Centre, an HIV clinic in Hong Kong, which provides care to around 3500 PLWH, with services including out-patient care of patients with human immunodeficiency virus (HIV) infection, antiviral therapy for HIV and hepatitis co-infection, and treatment of sexually transmitted diseases. PLWH with comorbidities will be asked to participate in a survey for willingness to participate. Those interested will be co-managed at the HIV Comorbidities Clinic at the Prince of Wales Hospital, where the DSD model of care is conducted. Evaluation of implementation outcomes will be performed at the end of the programme.

PLWH who are receiving effective and durable anti-retroviral therapy (ART) have similar life expectancy as the general population, but the patients do suffer from two-fold higher burden of disability associated with chronic comorbidities as compared with people without HIV infection. The screening and management of these chronic comorbidities are gaining attention in both high-income and low- and middle-income settings.

There are at present different models of care to deliver healthcare for the screening and management of comorbidities for PLWH. Fully integrated care of both HIV and comorbidities in a one-stop clinic brings numerous benefits, including optimal utilization of resources, provision of holistic care, and de-stigmatization; but also encounters various challenges, such as placing burden on human and spatial resources in HIV clinics, and the limited availability of co-medications in HIV clinics. In high-income settings, traditional models of care are often physician-centred, thus more innovative models have been explored, involving integrated care in the primary care setting, or consultations by multiple specialists in an integrated clinic, but these require a high magnitude of coordination and have resource implications, limiting feasibility universally. On the other hand, a "differentiated service delivery (DSD)" model is an adaptive model of care that aims to tailor healthcare delivery services according to patients' individual clinical needs and preferences, while taking into consideration resource availability in the local context. This model of care is successful in the delivery of HIV care and management of ART, and is patient-centred, offering patients a mode of care most optimal for their lifestyle and needs without imposing unmanageable burden on the healthcare system. DSD is advocated to be developed for the aging population of PLWH to provide patient-centred healthcare service for management of their comorbidities and other age-related issues, but has not been well studied.

The rising use of telemedicine since the Coronavirus disease 2019 (COVID-19) pandemic in the management of HIV and other chronic diseases would facilitate the incorporation of more patient-centred options in healthcare service delivery according to patients' needs and preferences. Telemedicine interventions improve access to care, control of disease, and quality of life in people with chronic non-communicable diseases. In particular, telemonitoring interventions and synchronous video teleconsultations are found to be beneficial in disease control and enhancing patient-physician interaction.

The currently proposed DSD model of care has the following benefits: (1) patient-centred care with individualized care delivery options according to patients' preference, such as offering teleconsultation as an alternative, options of different drug delivery modes, and personalized management plans according to individual clinical needs; (2) shared care between HIV care providers and internal medicine specialists, with close communication regarding clinical data and treatment plans, while avoiding duplication of resources; (3) draws on the availability of telemedicine tools in public healthcare services in Hong Kong; (4) patient empowerment by educating patients on treatment goals, performing selfmonitoring of disease, and scheduling appointments according to clinical indications; and (5) optimizing care of complex comorbidities by providing specialist care, and screening and management of comorbidities according to evidencebased guidelines.

Inclusion Criteria:

• PLWH eligible to participate in this study are PLWH aged 18 years or above
• followed up at the HIV Clinic, and with one or more cardiometabolic comorbidities, including hypertension, diabetes, hyperlipidaemia, metabolic-associated fatty liver disease, cardiovascular diseases, and cerebrovascular diseases. They will be eligible if HIV physicians consider them having sub-optimal control of their comorbidities, suspected of having complications, or would benefit from screening of complications resulting from their comorbidities. These indications are selected as they involve specialist care, including investigations and treatment, which are not available at the HIV Clinic.

Exclusion Criteria:

• Incompetent subjects who cannot give informed written consent.

PLWH eligible to participate in this study are PLWH aged 18 years or above followed up at the HIV Clinic, and with one or more cardiometabolic comorbidities, including hypertension, diabetes, hyperlipidaemia, metabolic-associated fatty liver disease, cardiovascular diseases, and cerebrovascular diseases.