*2.3. Data Extraction*

Qualitative and quantitative variables were collected in an ad hoc electronic form.

The following variables were collected: first author's last name; title of the article; year and country/countries of the study; period of the study; epidemiological study design; sample size; sex and age; type of samples; HPV detection methods; histological subtypes; tumor grading; HPV prevalence.

No ethical approval was needed given the anonymized and aggregated nature of the data.
