Objective: To estimate the size of the population of female sex workers (FSWs) on the basis of the HIV/AIDS behavioural surveillance approach in two Chinese cities, using a multiplier method.
Method: Relevant questions were inserted into the questionnaires given to two behavioural surveillance groups-female attendees of sexually transmitted disease (STD) clinics and FSWs. The size of the FSW population was derived by multiplying the number of FSWs in selected STD clinics during the study period by the proportion of FSW population who reported having attended the selected STD clinics during the same period.
Results: The size of the FSW population in the urban area of Xingyi, China, was estimated to be about 2500 (95% CI 2000 to 3400). This accounted for 3.6% of the total urban adult female population. There were an estimated 17,500 FSWs in the urban area of Guiyang, China (95% CI 10,300 to 31,900) or about 3.4% of its total urban adult female population (rounded to the nearest 100).
Conclusions: The multiplier method could be a useful and cost-effective approach to estimate the FSW population, especially suitable in countries where HIV behavioural surveillance has been established in high-risk populations.