According to the findings of the prevalence study conducted by Department of Health and Chinese University of Hong Kong in 2005 (Elderly Commission, 2005), among the 70,000 community-living older people suffering from dementia, 89% of them are not known to any medical services, which means 11% of people with dementia have received a diagnostic assessment at that time. No more updated figures on the diagnostic rate are available.

References:

Elderly Commission. (2005). Prevalence of dementia in Hong Kong. Retrieved from https://www.elderlycommission.gov.hk/en/download/meeting/Study%20on%20Prevalence%20of%20dementia.pdf