Figure 3.

Illustration of the components used to compute associations between drugs and medical conditions for signal detection using search logs. Each user is associated with a surveillance period (blue line) centered on the time of the users' first query ( ${\mathbf{T}}_{\mathbf{i}}^{\mathbf{0}}$) for a drug of interest (D). Associations are estimated by calculating the query rate ratio (QRR)—the ratio between the number of queries for a condition (C) or symptom (S) of interest outside the exclusion period (shaded region) after and before ${\mathbf{T}}_{\mathbf{i}}^{\mathbf{0}}$. In this example, QRR=(4+3+2)/(1+1+1)=3.