Quality of Life Research

, Volume 21, Issue 4, pp 637–650 | Cite as

Latent variable mixture models: a promising approach for the validation of patient reported outcomes

  • Richard SawatzkyEmail author
  • Pamela A. Ratner
  • Jacek A. Kopec
  • Bruno D. Zumbo



A fundamental assumption of patient-reported outcomes (PRO) measurement is that all individuals interpret questions about their health status in a consistent manner, such that a measurement model can be constructed that is equivalently applicable to all people in the target population. The related assumption of sample homogeneity has been assessed in various ways, including the many approaches to differential item functioning analysis.


This expository paper describes the use of latent variable mixture modeling (LVMM), in conjunction with item response theory (IRT), to examine: (a) whether a sample is homogeneous with respect to a unidimensional measurement model, (b) implications of sample heterogeneity with respect to model-predicted scores (theta), and (c) sources of sample heterogeneity. An example is provided using the 10 items of the Short-Form Health Status (SF-36®) physical functioning subscale with data from the Canadian Community Health Survey (2003) (N = 7,030 adults in Manitoba).


The sample was not homogeneous with respect to a unidimensional measurement structure. Specification of three latent classes, to account for sample heterogeneity, resulted in significantly improved model fit. The latent classes were partially explained by demographic and health-related variables.


The illustrative analyses demonstrate the value of LVMM in revealing the potential implications of sample heterogeneity in the measurement of PROs.


Self-report measurement Psychometrics Measurement validity Physical function 



Akaike information criterion


Bootstrapped likelihood ratio test


Bayesian information criterion


Sample-adjusted Bayesian information criterion


Canadian Community Health survey


Differential item functioning


Item response theory


Graded response model


Latent variable mixture model


Odds ratio


Patient reported outcomes


Vuong-Lo-Mendell-Rubin likelihood ratio test



This research was completed with support from the Michael Smith Foundation for Health Research, the Arthritis Research Centre of Canada, and the Canadian Arthritis Network. The research and analysis are based on data from Statistics Canada, and the opinions expressed do not represent the views of Statistics Canada.

Supplementary material

11136_2011_9976_MOESM1_ESM.docx (57 kb)
Supplementary material 1 (DOCX 57 kb)


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Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Richard Sawatzky
    • 1
    Email author
  • Pamela A. Ratner
    • 2
  • Jacek A. Kopec
    • 3
  • Bruno D. Zumbo
    • 4
  1. 1.School of NursingTrinity Western UniversityLangleyCanada
  2. 2.School of NursingUniversity of British ColumbiaVancouverCanada
  3. 3.School of Population and Public HealthUniversity of British Columbia; Arthritis Research Centre of CanadaVancouverCanada
  4. 4.ECPS, Measurement, Evaluation and Research MethodologyUniversity of British ColumbiaVancouverCanada

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