Test-retest reliability of the PDQ-Carer

The PDQ-Carer is a 29-item measure of health-related quality of life (QoL) for use with carers of people with Parkinson's (PwP). The measure produces a profile of scores across four domains. Previous validation data indicates that the measure possesses sound psychometric properties in terms of validity and internal consistency. An additional important attribute of any measure is test-retest reliability, i.e. the ability to provide stable results over time, presuming that there has been no change in the status of the construct being measured. To date, no assessment of the test-retest reliability of the PDQ-Carer has been undertaken.

Carers of PwP were recruited via Parkinson's UK. Participants completed the PDQ-Carer online on two occasions, two weeks apart. On second administration participants answered an additional question asking how much, if at all, their QoL had changed over the two week period. Subsequent analyses focused on those carers who reported no change in their QoL.

At first administration 142 carers fully completed the PDQ-Carer and at second administration 104 participants with no missing data responded. Seventy four of these participants (71.2%) reported no change in QoL and thus went forward to the final analysis. Intraclass correlation coefficients for each domain were calculated as follows: Social and Personal Activities .97; Anxiety and Depression .95; Self-Care .96; Stress .95 CONCLUSION: Results indicate that the PDQ-Carer demonstrates sound test-retest reliability and can be confidently used by researchers who wish to incorporate it in studies of carers of PwP.