Objectives:
The aim of the study was the validation and adaptation of the ORTO-15 Questionnaire in the group of the Polish schoolgirls and schoolboys.

Methods:
The study included 399 participants (15-21 years old), all of them high school students in the city of Sosnowiec. The ORTO-15 is a tool created in Italy by L.M. Donini, comprising of 15 items describing intensification of orthorexia risk (population diagnosis). The validation procedure incorporated three basic methods to be applied in the reliability analysis – the comparison of double tests with the same method, the statistical properties analysis of test items as well as analysis of the relation of test items with the general test result. Moreover, the compliance of the ORTO-15 Questionnaire results with other questionnaire focused on eating habits (EAT-26) was studied.

Results:
The reliability analysis of the ORTO-15 Questionnaire based on repeatability of the responses presents a very good (kappa: 0.81 – 1.00 for 5 items) and a good repeatability (kappa: 0.61 – 0.80 for 10 items). The reliability analysis based on the value of the Cronbach’s α reached a satisfactory level (0.7 – 0.9). A full agreement of in the occurrence of orthorexia risk and the risk of eating disorders concerned 47.2% (Kappa = 0.04; 95% CI: 0.004 – 0.09) for the Ortho-40 and 88.2% (Kappa = 0.32; 95% CI: 0.17 – 0.47) for the Ortho-35.

Conclusions:
The ORTO-15 questionnaire is a reliable tool to identify the risk of ON in population studies in the group of urban youth aged 15 – 21.