OBJECTIVES: This study analyses waiting times for patients submitted to surgical treatment in the Portuguese National Health Service (NHS), using all patients (amounting to more than 2.5 million observations) from 2011 to 2015. It tries to evaluate whether there are variables besides need or severity of the patients that explain variations in waiting times.

METHODS: Our study adds to the existing comprehensive literature on waiting lists using a methodology that offers more robust results. A High-Dimensional Fixed Effects model is estimated allowing a set of fixed effects to control the unobserved heterogeneity, since recent literature shows that these models perform better than the conventional models.

RESULTS: Controlling for the fixed effects (year, hospital of origin, county of residence, main procedure code, initial priority and age) that were shown to be significant, the results indicate that, on average, men have a shorter waiting time than women (about 3%). Waiting times are higher in the population aged 1 to 22 years. Patients aged over 69 years have waiting times that seem to gradually decrease. Children under one year old are those who also have lower waiting times.

Patients who were reported to have cancer wait less for surgery. Although hospital transfers occur in only 0.25% of cases, the results show that they are relevant to significantly reduce waiting times. The fixed effects also confirm that a higher level of priority is associated with shorter waiting times and that the organizational structure of hospitals explains some variation in waiting times.

CONCLUSIONS: Despite controlling for a variety of fixed effects, significant differences were found in waiting times. On the one hand, it is shown that there is a prioritization of patients on waiting lists, on the other, there are differences that appear to indicate a discriminatory conduct.