There are two types of casefinding methods used by registries: active and passive.
Active casefinding involves registry personnel retrieving all source documents (such as disease indices, pathology reports, etc.). These documents are then screened to identify reportable cases. The benefit of active casefinding procedures is that this method is more thorough and accurate than passive casefinding. Registry personnel have knowledge of criteria and terminology to recognize reportable cases. Review of each casefinding source requires additional processing time by the registry staff. The registry may lack the staff and financial resources necessary to allow registry personnel to actively review all potential casefinding sources.
Passive casefinding occurs when other departments notify the registrar of potentially reportable cases. A concern with passive casefinding is that non-registry staff are not as familiar with reporting criteria and terminology, so potential cases may be missed or incomplete casefinding may occur. For example, non-registry staff could miss the collection of cases with diagnostic terms that may not sound cancerous (such as linitis plastica or Waldenstrom's macroglobulinemia, or even leukemias and lymphomas).
A combination of active and passive casefinding is a commonly used system in registries today. The registrar must identify the critical casefinding sources that require active review by the registrar, decide the amount of passive case identification that should be performed, and determine which departments can provide high-quality casefinding information. An effective combination of active and passive reporting methods ensures more complete cases and reduces labor costs of the registry.