The impact of cancellations in waiting times analysis: evidence from scheduled surgeries in the Portuguese NHS

BACKGROUND: Equity in access to scheduled surgery has been a topic of attention of researchers and decision-makers on healthcare. Most studies analyse the number of days that patients wait before undergoing surgery, and ignore patients that have been on the waiting list but have not benefited from surgery. This study contributes to the existing literature on waiting lists by analysing cancellations along with surgery episodes. METHODS: We use a database comprising all patients that entered the waiting list for scheduled surgeries in the Portuguese National Health Service from 2011 to 2015 (around 3 million observations) and estimate survival models to explain waiting times, where cancellations are introduced as censored data. RESULTS: The cancellation rate is significant (around 14%), and has a considerable impact on results: ignoring cancellations biases estimates, in particular for gender differences (that are overestimated without cancelations), and for the age effect (that is underestimated). CONCLUSION: Thus, our approach provides a more accurate understanding of the impact that several factors have on overall access to scheduled surgery.