Monitoring laboratory effort is also useful when it focuses upon determining the outcome of discarded cases, i.e., the reasons why suspected cases of disease reported to our surveillance system are eventually ruled out as confirmed cases, because it gives us an indication of the quality of surveillance and case investigation efforts. More specifically, it helps us identify both problems in inadequate laboratory testing and incomplete case follow-up. This surveillance performance indicator is especially valuable when we combine it with zero reporting of diseases. (“Zero reporting” is the mandatory routine reporting to a surveillance system that no cases of disease have been detected during a specified time period when such is the case. This indicates to authorities that no cases of disease have been found even when appropriate surveillance has been in place to detect their presence). Examining discarded cases is especially valuable when conducting surveillance for a disease at or near the elimination or eradication stage. If we find little, and preferably no, cases discarded due to either inadequate laboratory testing or incomplete follow-up, and most, and preferably all, ruled out as confirmed cases using adequate laboratory testing and complete follow-up, then we can feel reasonably confident that when no cases of disease are reported to our surveillance system, it indicates the true absence of the disease in our community or population of interest.

- those that met the clinical case definition but were not ruled in or out as confirmed cases due to inadequate laboratory testing and

- those that did not meet the clinical case definition but could not be ruled in or out as confirmed cases due to incomplete follow-up.

The next slide demonstrates how these criteria were applied to non-confirmed measles cases reported to our surveillance system in 2001 to identify areas of the our surveillance system that needed improvement.