Trends in multidrug-resistant Mycobacterium tuberculosis in relation to sputum smear positivity in Hong Kong, 1989-1999.

We studied retrospectively the territory-wide occurrence and trends of multidrug-resistant tuberculosis (MDR-TB) in Hong Kong over an 11-year period during which a short-course directly observed therapy ("DOTS-Plus") strategy has been in operation. The overall MDR rate was 2.1% (primary, 1.4% and acquired, 9.5%) and declined at 0.08% per year: smear-positive primary MDR cases declined at yearly rate of -0.065% (R2=.23), and smear-negative primary MDR cases increased at 0.035% yearly. With declining rates of smear positivity, sputum culture has become the mainstay of detection of MDR-TB. Although the overall notification rates showed the elderly (age >65 years) age group to be most affected, the occurrence of MDR-TB has been consistently highest in the 35-65 year age group (60.4% of MDR caseload). We demonstrated declining rates of sputum smear positivity of MDR-TB in a DOTS-plus environment and that a centralized laboratory database is essential in gathering epidemiological information for identifying particular risk groups and monitoring trends of MDR-TB in a community.