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Assessing quality of data

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Overall, surveillance can be more timely and flexible than other data collection methods, but interpretation of the resulting data must be done carefully. Before reaching conclusions you should know a great deal about the surveillance system producing the data, such as:

  • Who reports the data? At what health facilities?
  • How complete is the reporting?
  • Approximately what proportion of patients with the disease actually seek medical care in reporting facilities?
  • What proportion of eligible health facilities report data regularly? Has this changed during the time period of interest?
  • Were there any changes in the surveillance system or case definition during the time period of interest?
  • Have there been any changes in the denominator used to calculate incidence rates?