Memo

In follow-up to yesterday's call, I wanted to clarify a number of things:
 - Data collection for population-based, lab-confirmed influenza hospitalization is currently ongoing by the Emerging Infections Program (EIP) sites, a voluntary partnership between the states and CDC.

 - Although at one point in time, sampling of adults hospitalized for influenza was considered (more adults than children are hospitalized with influenza), the EIP sites have not sampled for surveillance cases.

   In the event of a severe (1918 pandemic-like situation), it may be necessary for sites to sample cases.  However, for seasonal or non-1918 pandemic influenza, the severity of an influenza season cannot be predicted and sampling poses a significant challenge if data reliability is not to be compromised.  A number of factors are associated with increased influenza morbidity, including vaccine mismatch, influenza strain drift/shift, and epidemiologic risk factors for influenza hospitalization (eg, age, chronic conditions, present medical condition, etc).  In summary, before the start of influenza season it would be extremely difficult (if not impossible) to decide on a method and then implement a stratified sampling scheme that all EIP sites could follow.

 - A surveillance system is only as good as the data it yields.  As part of evaluating the completeness of case ascertainment, EIP sites are to complete a one-time discharge audit by linking their surveillance cases to their state hospital discharge database.  By identifying missed cases, an EIP site may need to include more hospitals as part of their surveillance catchment area so they do not continue to under ascertain cases.  The discharge audit is intended as a "quality control" evaluation for a single site.  Summary data from the site should be shared with CDC so that an estimate of case completeness can be calculated.  While each sites' case completeness provides useful information about the overall quality of EIP data--eg, completeness of case ascertainment ranged from xx to yy%--it was never intended that all sites' audit information would be aggregated and analyzed together.

Thanks,

Petunia L. Gissendaner
Information Collection Review Administrator
Information Collection Review Office
Office of Scientific Regulatory Services
Office of the Chief Science Officer
Centers for Disease Control and Prevention (CDC)
1600 Clifton Rd., NE (Mail Stop D-74)
Atlanta GA  30333
404-639-0164
Fax 404-639-3060
[email protected]