Anesthesia and Circulating Tumor Cells: Reply

We thank Dr. Zhu et al. for their valuable inputs¹  regarding our study.²  Dr. Zhu rightly points out that there is a relatively large proportion of zeros in our data set, which may support the use of mixed zero-inflated Poisson models. In our case, however, the use of such statistical approach was not formally indicated: the rationale underlying zero-inflation is that certain individuals might—because of some unknown factors—not be able to present values other than zero. If this is indeed the case, the logistic regression part of zero-inflated models is used to model that inability. In our trial, though, in-depth review of our longitudinal data revealed that most patients presented values other than zero on at least one of the time points. Most notably, the percentage of patients presenting zero values over the entire observation...