Confirming the factor structure of a generic quality of life instrument among pre-treatment substance use disorder patients

Ashley Elizabeth Muller,Svetlana Skurtveit,Thomas Clausen

doi:10.1186/s12955-019-1152-7

Abstract

BackgroundQuality of life (QoL) is a patient-reported outcome of increasing importance in the substance use disorder (SUD) treatment field, and impaired QoL may be an important impetus for treatment uptake. Instruments and methodologies abound, precluding comparison, as does a dearth of population norms. The QOL10 is a generic, overall QoL tool containing ten items and with simple scoring procedures. It is therefore a potential alternative to the gold standard WHOQOL-BREF. This study aimed to assess the two-factor structure of the QOL10 that has been suggested by a previous exploratory factor analysis.MethodsAdults entering 21 participating inpatient or outpatient SUD treatment were recruited to join a national longitudinal cohort study. 531 completed the QOL10 at treatment entry and were included in the analysis. Structural equation modelling (SEM) was used to confirm the model fit of a two-factor structure, and the scaling qualities of the QOL10 were reported.ResultsAccording to the SEM analysis, the QOL10 was comprised of one latent variable measuring social QoL, and one measuring global QoL, and all ten items were retained. Goodness of fit tests included: root mean square of approximation = 0.063, 90% CI 0.050–0.076; normed-fit index = 0.919; and comparative fit index = 0.943.ConclusionsThe QOL10 should be considered when clinicians in the SUD treatment field need a short, valid instrument that measures both global QoL and social QoL, with minimum respondent and administrator burden. The social domain is of particular utility and may be used as a stand-alone instrument. Test-retest reliability should be established in future studies.

Highlights

Quality of life (QoL) is a patient-reported outcome of increasing importance in the substance use disorder (SUD) treatment field, and impaired QoL may be an important impetus for treatment uptake
The remainder of the indices indicated that the model was a good fit: normed-fit index = 0.919; comparative fit index = 0.943; and root mean square error of approximation = 0.063, 90% CI 0.050–0.076
In the German study, a different instrument with the same scoring scale was used, and three social domain scores ranged from 42 to 57, while the general QoL domain score was 38. These results should not be interpreted as this sample or others with substance use disorders having acceptable social QoL, rather, that their global QoL – accounting for health, working ability, and an overall QoL evaluation – is extremely impaired

Summary

Introduction

Quality of life (QoL) is a patient-reported outcome of increasing importance in the substance use disorder (SUD) treatment field, and impaired QoL may be an important impetus for treatment uptake. The International Society for Quality of Life Research suggests minimum standards for QoL instruments in addition to validity and reliability, such as a low burden to both respondents and administrators, i.e. using a minimum amount of items and simple scoring procedures [9]. A validation study reported that some of the negatively worded items may not have been understandable by substance users [12] Another commonly used measure, the Lancashire Quality of Life Profile (LQoLP) [13], is psychometrically strong but imposes even more burden, with 133 items administered in a structured interview

Objectives

Methods

Results

Discussion

Conclusion