Value of ICD-9-Coded Chief Complaints for Detection of Epidemics

To assess the value of ICD-9-coded chief complaints for early detection of epidemics, we measured sensitivity, positive predictive value, and timeliness of Influenza detection using a respiratory set (RS) of ICD-9 codes and an Influenza set (IS). We also measured inherent timeliness of these data using the cross-correlation function.