This section deals with periodic surveys that have requirements that prevent them from being added to the routine core update survey rounds. Usually they require more time at the household because of the length of the questionnaire or the requirement for biomarker collection or testing.  This work typically needs special training of dedicated survey team working on a sub-sample of the DSS population. Many of these surveys deal with effective coverage (the combined effect of access, diagnostic targeting, provider compliance and patient adherence on intervention efficacy).  The prime advantage of DSS sites is that each of these determinants of coverage can be assessed by equity quintile to determine the equity effectiveness of the interventions.