Assessing quality of data
(go to Outline)
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?