Equivalence of Various Language Versions of Lupus Specific Patient Reported Outcomes Measure (LupusPRO)

Meenakshi Jolly¹, Mark Kosinski², Sergio M.A. Toloza³, Joel A. Block⁴, Rachel A. Mikolaitis⁴, Sergio Durán-Barragan⁵, Ana M. Bertoli⁶, Ivana Blazevic⁷, Luis M. Vila⁸, Dilrukshie Cooray⁹, Emmanuel P. Katsaros¹⁰, Karina Marianne D. Torralba¹¹, Ioana Moldovan¹², Arif Kaya¹³, Berna Goker¹³, Seminur Haznedaroglu¹⁴, Mehmet E. Tezcan¹³, Josiane Bourré-Tessier¹⁵, Sasha Bernatsky¹⁶, Ann E. Clarke¹⁷, Michael H. Weisman¹⁸, Sandra V. Navarra¹⁹, Daniel J. Wallace²⁰ and Graciela S. Alarcon²¹, ¹Rheumatology, Rush University Medical Center, Chicago, IL, ²QualityMetric Inc, Lincoln, RI, ³Medicine, Hospital San Juan Bautista, Catamarca, Argentina, ⁴Section of Rheumatology, Rush University Medical Center, Chicago, IL, ⁵Unidad de Investigacion en Enfermedades Cronico-Degenerativas, Guadalajara, Mexico, ⁶Instituto Reumatológico Strusberg, Cordoba, Cordoba, Argentina, ⁷University of Buenos Aires, Buenos Aries, Argentina, ⁸Department of Medicine, Division of Rheumatology, University of Puerto Rico Medical Sciences Campus, San Juan, PR, ⁹Rheumatology, Harbor UCLA Medical Center, Torrance, CA, ¹⁰Int Medicine, Loma Linda Univ, Loma Linda, CA, ¹¹Rheumatology/Int Med, USC Keck Schl of Medicine, Los Angeles, CA, ¹²Loma Linda Univ Medical Center, Loma Linda, CA, ¹³Internal Medicine-Rheumatology, Gazi University Medical School, Ankara, Turkey, ¹⁴Internal Medicine-Rheumatology, Gazi University School of Medicine, Ankara, Turkey, ¹⁵Rheumatology, McGill University, Montréal, QC, Canada, ¹⁶Clinical Epidemiology, Research Institute of the McGill University Health Ctre, Montreal, QC, Canada, ¹⁷Division of Rheumatology, University of Calgary, Alberta, Calgary, AB, Canada, ¹⁸Rheumatology, Cedars-Sinai Medical Center, Los Angeles, CA, ¹⁹University of Santo Tomas Hospital, Manila, Philippines, ²⁰Cedars-Sinai Medical Center, Los Angeles, CA, ²¹Medicine, University of Alabama at Birmingham, Birmingham, AL

Meeting: 2012 ACR/ARHP Annual Meeting

Keywords: Health Assessment Questionnaire, outcome measures and systemic lupus erythematosus (SLE)

Session Information

Title: Systemic Lupus Erythematosus: Clinical Aspects

Session Type: Abstract Submissions (ACR)

Background/Purpose: Due to observed disparities in health outcomes in Systemic Lupus Erythematosus (SLE) across racial/ethnic groups, socioeconomic status, or health care systems, studies on group comparisons can highlight important contextual influences on health outcomes. However, comparative research requires the measurement tool used to quantitate such health outcomes to have similar measurement qualities across settings (Measurement Equivalence). This property focuses on the internal structure of multi-item instruments. Currently measurement equivalence data is not available on any of the SLE specific patient reported outcome tools. Herein, we present measurement equivalence properties of various language versions of the LupusPRO that were tested across nations.

Methods: Data from the SOUL study (Study of Outcomes in Lupus) collected during cross-cultural validation studies of the LupusPRO in various languages were utilized: English [USA (n=180), Canada (n=123), Philippines (n=100)], Spanish [USA (n=121), Mexico (n=34), Argentina (n=56)] and Turkish (Turkey n=102). Confirmatory factor analysis (CFA) was conducted with the LupusPRO ítem responses using a robust weighted least squares estimator. The goodness of fit parameters used were the Comparative Fit Index (CFI) and Tucker-Lewis Index (TLI). In addition, item to factor loadings were tested. For measurement equivalence, a logistic regression approach was used to test for differential Item functioning (DIF) in each LupusPRO scale item across languages, while conditioning on the aggregate sum score for each LupusPRO score. The magnitude of DIF was quantified by a pseudo R² difference measure and ≥2 % variance was considered significant DIF across languages

Results: Results of the CFA lend empirical support for the conceptual framework of the LupusPRO across languages. The model fit for the hypothesized item to scale relationships was good (CFI=0.94-0.98, TLI=0.95-0.99). In addition, item to factor representing the hypothesized item to scale relationships were also satisfactory. In general, items loaded >0.6 with their respective factor. Of the 43 LupusPRO items, only 6 items showed a marginal DIF: (1) woke up feeling worn out, (2) worried about losing income, (3) lacked control over appearance, (4) ability to plan activities and schedule events, (5) received comfort/strength from spiritual/religious beliefs, and (6) doctor was accessible when I had questions. Some of these could be due to cultural differences.

Conclusion: Since the LupusPRO demonstrates measurement equivalence across languages, it can now be used for comparative research studies to gain better insight into health outcomes disparities or effects of interventions across various groups of SLE patients in cross-national studies. Further evaluation and analysis of the items showing DIF are ongoing.

Disclosure:

M. Jolly,

GlaxoSmithKline,

MedImmune,

The Binding Site,

Lupus Foundation of America,

M. Kosinski,
None;

S. M. A. Toloza,
None;

J. A. Block,
None;

R. A. Mikolaitis,
None;

S. Durán-Barragan,
None;

A. M. Bertoli,
None;

I. Blazevic,
None;

L. M. Vila,
None;

D. Cooray,
None;

E. P. Katsaros,
None;

K. M. D. Torralba,
None;

I. Moldovan,
None;

A. Kaya,
None;

B. Goker,
None;

S. Haznedaroglu,
None;

M. E. Tezcan,
None;

J. Bourré-Tessier,

GlaxoSmithKline ,

S. Bernatsky,
None;

A. E. Clarke,
None;

M. H. Weisman,
None;

S. V. Navarra,

HGS, GSK,

D. J. Wallace,

HGS, GSK,

G. S. Alarcon,
None.

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