information for practice

news, new scholarship & more from around the world


advanced search

The validity of subjective quality of life measures in psychotic patients with severe psychopathology and cognitive deficits: an item response model analysis

Abstract

Purpose  

Subjective quality of life (SQOL) is an established patient-reported outcome in the evaluation of treatments for psychosis.
The use of SQOL measures in the presence of psychiatric symptoms and cognitive deficits has been questioned. However, there
is little evidence on whether items function differently as indicators of SQOL in psychotic patients with different levels
of symptoms and deficits. Substantial differential item functioning (DIF) would, indeed, challenge the validity of established
measures. We aimed to investigate the validity of a widely used measure of subjective quality of life (SQOL), i.e., the Lancashire
Quality of Life Profile (LQOLP), in the presence of cognitive deficits and psychiatric symptoms in patients with severe and
enduring psychosis.

Method  

We analysed SQOL ratings of 690 psychotic patients on the LQOLP using item response modelling to detect differential item
functioning (DIF) attributable to psychiatric symptoms and cognitive deficits.

Results  

Patients with more severe general psychopathology were less likely to rate their ‘personal safety’ positively (OR .96, 95%
CI .93–.99). More severely depressed patients were less likely to endorse positive ‘life as a whole’ (OR .93, 95% CI .89–.98)
and ‘mental health’ (OR .93, 95% CI .91–.97) ratings. There was no DIF attributable to cognitive deficits.

Conclusions  

The findings suggest that the validity of the LQOLP in psychotic patients may be impaired by DIF due to psychopathology, although
the magnitude of effects is unlikely to be of clinical significance. The validity appears not to be compromised by cognitive
deficits.

  • Content Type Journal Article
  • Pages 1-10
  • DOI 10.1007/s11136-011-9936-1
  • Authors
    • Ulrich Reininghaus, Unit for Social and Community Psychiatry, Barts and the London School of Medicine, Newham Centre for Mental Health, Queen Mary University of London, London, E13 8SP UK
    • Rosemarie McCabe, Unit for Social and Community Psychiatry, Barts and the London School of Medicine, Newham Centre for Mental Health, Queen Mary University of London, London, E13 8SP UK
    • Tom Burns, Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford, OX3 7JX UK
    • Tim Croudace, Department of Psychiatry, University of Cambridge, Addenbrooke’s Hospital, Cambridge, CB2 2QQ UK
    • Stefan Priebe, Unit for Social and Community Psychiatry, Barts and the London School of Medicine, Newham Centre for Mental Health, Queen Mary University of London, London, E13 8SP UK