Among case detection studies, cluster testing is useful in detecting cases of:

Cluster testing is used for detecting STDs. Here the patients are asked to name other persons of either sex who move in the same socio-sexual environment. These persons are then screened (e.g., blood testing). This testing has been shown almost to double the number of cases found. Ref: Textbook of Preventive and Social Medicine by K Park, 19th edition, Page 281.