The SCALA study will test the hypothesis that the scale-up of implementing a tailored intervention package embedded in a wider strategy of community and municipal support in Latin American cities, will increase screening and advice rates more than the usual practice, carried out by health care providers alone.

SCALA will use a quasi-experimental study to compare PHC-based prevention and management of heavy drinking and co-morbid depression in three intervention districts (municipal areas) within three Latin American cities with service as usual in three comparator districts in the same cities.

The cities taking part in the trial are Bogota (Colombia), Mexico City (Mexico) and Lima (Peru), where matched districts or boroughs (locally governed municipal areas) will be identified and assigned to either “scale-up”/implementation or control conditions. In the implementation districts, primary health care units (PHCUs) will receive training embedded within on-going supportive action at the municipal level (local government, workforce and infrastructure), over an 18-month implementation period. In the comparator districts, practice as usual will continue at both municipal and PHCU levels.

Study summary diagram