Validation and Reliability of Polish Version of the Reflux Symptoms Index and Reflux Finding Score

(1) Background: To confirm the credibility, consistency, and replicability of the Polish versions of the Reflux Symptoms Index (PL-RSI) and the Reflux Finding Score (PL-RFS). (2) Methods: The translation followed the WHO recommendations. The study group included 100 volunteers (age 15-87) with hoarseness and pharyngolaryngeal complaints. The control group comprised 55 healthy volunteers (age 20-75). Study participants completed the PL-RSI; then, two independent otolaryngologists completed the PL-RFS based on pharyngeal videostroboscopy. Questionnaires were repeated after 7 days, with no treatment before the second round. Additionally, patients underwent 24 h pH-metry. The control group had a single round of questionnaires followed by pH-metry. (3) Results: The PL-RSI is consistent, reliable (Cronbach's alpha 0.77-0.83; test-retest reliability 0.83), and significantly correlated with other patient-filled tools (p < 0.001). The PL-RFS intra-rater reliability is 0.84-0.91, and inter-rater is 0.88. Both questionnaires strongly correlate with pH-metry (PL-RSI upright Ryan Score 0.35, PL-RFS-0.60). Both clearly distinguish (i) healthy from persons with voice disorders, but without acid LPR (p < 0.0001), and (ii) within patient group between subjects with and without acid LPR (p = 0.0002). (4) Conclusions: The PL-RSI and PL-RFS are reliable and can be recommended to Polish-speaking otolaryngologists. Our findings confirm the role of country-specific factors in RSI results and that practitioners should always use a proper control group.