Quality of Life Research

, Volume 22, Issue 5, pp 1135–1144

Measurement invariance of the SF-12 across European-American, Latina, and African-American postpartum women

  • Tamer F. Desouky
  • Pablo A. Mora
  • Elizabeth A. Howell
Article

DOI: 10.1007/s11136-012-0232-5

Cite this article as:
Desouky, T.F., Mora, P.A. & Howell, E.A. Qual Life Res (2013) 22: 1135. doi:10.1007/s11136-012-0232-5

Abstract

Purpose

The purpose of this study was to determine whether a postpartum-specific version of the SF-12 was invariant across three ethnic groups. Specifically, we examined the presence of differential item functioning (DIF) among European-American, Latina, and African-American mothers. DIF refers to differential endorsement of item responses that are not due to the construct being measured. DIF can result in biased group comparisons.

Methods

We analyzed cross-sectional data of postpartum women (n = 655) who delivered at an urban hospital in the northeast region of the USA. Multiple indicators multiple causes (MIMIC) model was used to examine differential item functioning.

Results

The analyses revealed the presence of DIF for three items: Item 1 “self-assessed general health,” item 8 “bodily pain,” and item 9 “calm and peaceful.” Only two DIF effects were meaningful based on odds ratios and on the percentage of the total effect accounted for by the DIF effect. Specifically, African-American women differentially endorsed item 8 “bodily pain” when compared to European-American women (OR = 2.11, CI95 = 1.20, 3.71) and Latinas were more likely to endorse item 9 “calm and peaceful” when compared to European-American women (OR = 2.62, CI95 = 1.64, 4.17).

Conclusion

The results of this study indicate that the SF-12 is to a great degree an invariant measure for the assessment of HRQoL among postpartum ethnically diverse women. More research is needed to examine other aspects of invariance (e.g., configural and metric) and longitudinal invariance in ethnically diverse samples. To better understand ethnic differences in health, future studies need to examine the factors that may underlie DIF effects in quality of life.

Keywords

SF-12Structural equation modeling (SEM)Multiple indicators multiple causes modeling (MIMIC)Differential item functioning (DIF)PostpartumQuality of life

Abbreviations

SF-12

Short-form health survey

MIMIC

Multiple indicator multiple causes

DIF

Differential item functioning

HRQoL

Health-related quality of life

MOP

Maternity outcomes project

PCS

Physical component summary

MCS

Mental health component summary

SEM

Structural equation modeling

CFS

Confirmatory factor analysis

WLSMV

Weighted least squares mean and variance adjusted estimator

MLR

Maximum likelihood estimator with robust standard errors estimator

MCAR

Missing completely at random

OR

Odds ratio

χ2

Chi-square test

CFI

Comparative fit index

TLI

Tucker–Lewis index

RMSEA

Root mean square error of approximation

WRMR

Weighted root mean square residual

Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • Tamer F. Desouky
    • 1
  • Pablo A. Mora
    • 1
  • Elizabeth A. Howell
    • 2
  1. 1.Department of PsychologyThe University of Texas at ArlingtonArlingtonUSA
  2. 2.Department of Obstetrics and GynecologyMount Sinai Medical CenterNew YorkUSA