The Italian version of the scale most often used to determine quality of life in patients with Parkinson’s disease (PD) — the self-report 39-Item Parkinson’s Disease Questionnaire (PDQ-39) — has been validated for Italian patients, a study reports.
The Italian form of the survey (PDQ-39-IT) can now reliably be used in clinical practice and research to measure the effect of treatments in the quality of life of Italian Parkinson’s patients.
The study, “Quality of life in Parkinson’s disease: Italian validation of the Parkinson’s Disease Questionnaire (PDQ-39-IT),” was published in the journal Neurological Sciences.
The PDQ-39 has been the most widely used measure of health status and quality of life in Parkinson’s patients. It is helpful not only for clinical practice but also for research as an outcome measure in clinical trials testing potential treatments.
It is a scale designed specifically for Parkinson’s patients, containing 39 questions that ask how often patients have difficulties in eight domains: mobility, activities of daily living, emotional well-being, stigma, social support, cognition, communication, and bodily discomfort.
Since its development in 1995, the questionnaire has been translated, culturally adapted, and validated into 13 different languages.
Before a test can be employed for research or examination purposes, its validity needs to be ensured, and although an Italian translation and adaptation of this test was launched in 2008 — the PDQ-39-IT — its validity had never been verified.
Researchers have now tested the PDQ-39-IT in 104 patients diagnosed with Parkinson’s disease (mean age 65.7, mean duration of symptoms 7.4 years). Participants were recruited from June to October 2017 from two university hospitals in Rome: the Sapienza University and Tor Vergata University.
An important measure of a scale’s reliability is its internal consistency — that is, how closely related the items within a test are as a group.
To address this, researchers used a statistical coefficient called the Cronbach’s alpha. Except for social support, all other dimensions surveyed by PDQ-39-IT displayed a high Cronbach’s alpha of 0.70 or above. They were also within the range of those found in the original version of the test.
Researchers also examined another measure of a test’s coherence, called test-retest reliability. A subgroup of 35 patients was asked to complete the survey twice, with an interval of three days between the surveys. The scores obtained in the two surveys were compared. There was a high level of agreement between the test and the retest scores for all dimensions tested.
As a measure of the test’s validity, researchers compared the scores obtained in PDQ-39-IT for each patient with those obtained with the Italian version of 36-Item Short Form Health Survey (SF36) — another well-established patient-reported measure of health status.
All dimensions of PDQ-39-IT showed a positive and significant association with the SF-36 questionnaire, again demonstrating the test’s validity.
Overall, the study indicates that PDQ-39-IT “is an acceptable, valid, and reliable tool to measure the quality of life of Italian [Parkinson’s] patients,” researchers wrote.
“It provides Italian clinicians with a valid, reliable, rapidly administrable, and standardized scale to measure quality of life in [Parkinson’s disease], thereby enabling clinicians in all healthcare and rehabilitation professions to make informed decisions,” they added.
In addition, the test is a valuable tool to address the outcome of interventions over the quality of life of Italian Parkinson’s patients participating in clinical trials.