ORIGINAL CONTRIBUTION The GA 2 LEN survey for chronic rhinosinusitis prevalence studies: Arabic translation, cultural adaptation, and validation* Abstract Background: Chronic rhinosinusitis (CRS) is a common disease that significantly impacts quality of life. Its prevalence varies between different geographical areas. This study aimed to validate the Arabic version of the EPOS criteria in the GA2LEN question- naire to use it as a tool to estimate the prevalence of CRS in Arab countries. Methods: This is multicentric cross-sectional validation study. The original English EPOS criteria used in the GA2LEN survey (four main questions and two additional questions) were translated into Arabic. The study was conducted at King Abdulaziz University Hospital – Riyadh and Qatif Central Hospital – Qatif in the period between October 2020 and August 2021. Groups of CRS and non-CRS patients were selected randomly from databases of the hospital and asked to participate in the study through phone calls. Sensitivity, specificity, positive, and negative predictive values were calculated for the Arabic questionnaire. Results: Of 200 subjects contacted to complete the questionnaire, 128 agreed to participate and completed the survey. The Arabic version of the GA2LEN questionnaire was found to be reliable with high sensitivity and specificity. The reliability of the questionnaire increased when we added the question, “Has a doctor ever told you that you have chronic sinusitis?” to the main four questions. The sensitivity, specificity, and positive and negative predictive values were 93.9%, 59.6%, 71.25%, and 90.2%, respectively. Conclusions: The Arabic version of the EPOS criteria in the GA2LEN questionnaire is a valid and reliable tool for epidemiological studies to estimate the prevalence of CRS. Key words: Arabic questionnaire, chronic rhinosinusitis, diagnosis, epidemiology, prevalence, survey Hussain Albaharna 1,2,# , Saad Alsaleh 2,# , Abdulaziz AlQahtani 3 , Osama Marglani 4 1 Department of Otolaryngology - Head and Neck Surgery, Qatif Central Hospital, Qatif City, Saudi Arabia 2 Department of Otolaryngology - Head and Neck Surgery, College of Medicine, King Saud University, Riyadh, Saudi Arabia 3 Department of Otorhinolaryngology - Head and Neck Surgery, King Fahad Medical City, Riyadh, Saudi Arabia 4 Department of Ophthalmology and Otolaryngology, Head and Neck Surgery, Umm Al-Qura University, Makkah, Saudi Arabia Rhinology Online, Vol 5: 137 - 141, 2022 http://doi.org/10.4193/RHINOL/22.014 *Received for publication: June 1, 2022 Accepted: August 11, 2022 Published: September 26, 2022 # Shared first authorship 137 Introduction Chronic rhinosinusitis (CRS) is the inflammation of the sinona- sal mucosa lasting for more than 12 weeks (1) . According to the latest classification adopted by EPOS, CRS can be primary or secondary. For each group, the disease may be due to different endotype dominances leading to various phenotype expres- sions (1) . Epidemiologically, prevalence studies are essential to deve- loping a health economic module for any disease. Moreover, stu- dying the prevalence will inform policymakers about the disease burden, supporting the identification of priorities in healthcare, prevention, and policy (2) . Many epidemiological studies have been conducted worldwide on the prevalence of CRS. Diffe- rent techniques have been used to diagnose CRS among the study populations (3-7) . The Global Allergy and Asthma European Network of Excellence (GA 2 LEN) conducted one of the largest epidemiological studies to estimate the prevalence of CRS in 12 European countries (5) . They structured a questionnaire to diagnose CRS according to the 2007 EP 3 OS criteria. In the next step, the questionnaire was validated to the findings from nasal