David is an expert in primary healthcare services for disadvantaged, marginalised and vulnerable (underserved, priority) patient populations with complex needs in Australia. 

He is ranked 3rd in the Asia-Pacific region (SciVal 2020-2024, by outputs) and in the top 1% of international researchers in primary health (ScholarGPS, last 5 years), with 6.5 times higher than the world-average research impact in surgery and 3.5 times in evidence-based medicine (InCites Category Normalised Citation Impact, July 2023). David and his team have been awarded some $9.9 million in grants.

David's research has had significant real-world impact. For instance, his earlier work on evaluating the health policy of rural doctors dispensing drugs is now referenced in the World Health Organization guidelines on country pharmaceutical pricing policies, OECD's One Health Framework, Texas Public Policy Foundation's Doctor-to-Patient medication program, and Cochrane's systematic review on delivery arrangements for health systems; and, has influenced changes to the Australian Government policy in approval of community pharmacy. Similarly, his work on biosimilars has contributed to the Australian Biosimilar Awareness Initiative and was picked up by the media during the then-TransPacific Agreement negotiation. His recent research on rural general practice management of high-acuity caseloads is cited in the Pan American Health Organization's essential health services policy and Generalitat de Catalunya policy on primary care, and informed a current program of work on primary care disaster management. The commissioned work on Indigenous youth mental health is "highly influenced" and included in the Closing the Gap resource toolkit. The disability care work is included in the WA Disability Health Framework 2015-25, further demonstrating the practical implications of David's work.

David's dedication to primary healthcare reform and patient care is not just academic; it is rooted in over a decade of hands-on experience in rural and remote Australia. His time in these areas was marked by efforts to influence primary healthcare reform and improve patient care, a testament to his commitment to collaborative partnership and understanding of the healthcare needs of diverse populations.