The calculated Pearson correlation coefficient for PDQL, HY and UPDRS ranged between -0.42 and -0.79; the comparison of these variables are given in Table I.
Therefore, we performed a translation process using the PDQL English version that was prepared following the guidelines of the MAPI Research Institute (15).
PDQL-TR, HY and UPDRS total and subdomain scores were found to be significantly correlated with each other Many other studies showed similar results for the different versions of PDQL in the literature (28,29).
Our findings, presented in the Table 2, were similar and comparable to the original version of PDQL and the other versions of the questionnaire in the literature.
Another study published in 2007 reported that test-retest analysis of PDQL remained unexplored till their study and the authors concluded that their study results were satisfactory (30).
It would be much better to compare PDQL with another disease-specific quality of life questionnaire in Parkinson's disease, such as PDQ-39; however; the lack of quality of life questionnaires specific to Parkinson's disease in Turkish was a limitation to perform this type of comparison.
We can thus conclude that the psychometric features of PDQL-TR are satisfactory, and our results are consistent with the previous literature findings, including different version studies of PDQL. We may infer that PDQL-TR is a valid and reliable tool to measure health-related quality of life in patients with Parkinson's disease, and it is easy to understand its use and administer it as a self-administered questionnaire.
Translation, Cross-Cultural Adaptation, and Validation of the Parkinson's Disease Quality of Life Questionnaire (PDQL), the "PDQL-BR", into Brazilian Portuguese.