Fig. 2.
Graphical representation of the mixed-effects regression analysis on the incidence of postoperative nausea and vomiting (PONV) (A) and on administration of prophylactic antiemetics by anesthesiologists (B). The solid lines and their 95% CIs represent the fixed effects of the mixed-effects regression analyses. The dotted vertical line shows the intersection point of both groups. The mixed-effects models included fixed effects for the variables such as allocation group, predicted risk of PONV, interaction between allocation group and predicted risk, and time. Random effects were included for the intercept, predicted risk, interaction between allocation group and predicted risk, and time. The lines were calculated using the average for the variable time. The 95% CIs were calculated from the covariance matrix for the variables allocation group and its interaction term with predicted risk. (A) May be interpreted as the occurrence of PONV after receiving prophylaxis, in patients with a particular predicted risk within each group. The differences between the blue and red areas represent the effect of implementation of the prediction model on the occurrence of PONV in patients with a particular predicted risk. (B) May be interpreted as the number of prophylactic antiemetics a patient with a particular predicted risk of PONV would receive from any anesthesiologist within each group. The differences between the blue and red areas therefore represent the changes in physician behavior concerning prescription of antiemetic prophylaxis, caused by implementation of the prediction model.