Reliability and cross-cultural validity of the Bulgarian version of IRES-3

The IRES-3 questionnaire (Indicators of rehabilitation status, version 3) was developed to evaluate the rehabilitation effect in patients with psychosomatic, cardiac, orthopedic, oncologic, neurologic, gastroenterological and other disorders.

The aim of the present study was to validate the Bulgarian version of IRES-3 and assess its reliability and internal consistency.

Validation of the IRES-3 questionnaire was carried out at the Specialized Rehabilitation Hospital, the National Complex PLtd, the Hisar branch. The study included 46 patients: 14 males (30.43%) and 32 females (69.57%). Patients' age ranged between 43 and 75 years (mean age 63.52 +/- 1.27). All participants got preliminary instructions and after that, within a period of one week, they completed the questionnaire two times. To evaluate IRES-3 reliability we used the split-half-reliability model and calculated the Spearman-Brown coefficients (rsb) for each of the scales. Internal consistency was estimated using Cronbach's alpha coefficient. We used the mean value of the inter-item correlation coefficients as well.

The high values of rsb and Cronbach's coefficient alpha as well as the low values of the inter-item correlation coefficient which were obtained in our study demonstrate that the questionnaire under investigation is of high reliability and internal consistency. Our results are very similar to the results of the original German questionnaire which have been reported in literature.

The Bulgarian version of the IRES-3 questionnaire shows high reliability and cross-cultural validity and can be applied widely for evaluation of the effect of rehabilitation.