Propensity Score Methods in Rare Disease: A Demonstration Using Observational Data in Systemic Lupus Erythematosus

Ibrahim Almaghlouth; Eleanor Pullenayegum; Dafna D Gladman; Murray B Urowitz; Sindhu R Johnson

doi:10.3899/jrheum.200254

Propensity Score Methods in Rare Disease: A Demonstration Using Observational Data in Systemic Lupus Erythematosus

J Rheumatol. 2021 Mar;48(3):321-325. doi: 10.3899/jrheum.200254. Epub 2020 Jul 1.

Authors

Ibrahim Almaghlouth¹, Eleanor Pullenayegum², Dafna D Gladman³, Murray B Urowitz³, Sindhu R Johnson⁴

Affiliations

¹ I. Almaghlouth, MBBS, MSc, Division of Rheumatology, Department of Medicine, University of Toronto, Ontario, Canada, and Rheumatology Unit, Department of Medicine, and College of Medicine Research Center, King Saud University, Saudi Arabia.
² E. Pullenayegum, PhD, Division of Biostatistics, Dalla Lana School of Public Health, University of Toronto, and Program in Child Health Evaluative Sciences, SickKids Research Institute, Toronto, Ontario, Canada.
³ D.D. Gladman, MD, FRCPC, M.B. Urowitz, MD, FRCPC, Division of Rheumatology, Department of Medicine, University of Toronto, and Centre for Prognosis in Rheumatic Diseases, University Health Network, and The Krembil Research Institute, University Health Network, Toronto, Ontario, Canada.
⁴ S.R. Johnson, MD, PhD, Division of Rheumatology, Department of Medicine, and Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada. Sindhu.Johnson@uhn.ca.

PMID: 32611674
DOI: 10.3899/jrheum.200254

Abstract

Observational studies allow researchers to understand the natural history of rheumatic conditions, risk factors for disease development, and factors affecting important disease-related outcomes, and to estimate treatment effect from real-world data. However, this design carries a risk of confounding bias. A propensity score (PS) is a balancing score that aims to minimize the difference between study groups and consequently potential confounding effects. The score can be applied in 1 of 4 methods in observational research: matching, stratification, adjustment, and inverse probability weighting. Systemic lupus erythematosus (SLE) is a rare disease characterized by a relatively small sample size and/or low event rates. In this article, we review the PS methods. We demonstrate application of the PS methods to achieve study group balance in a rare disease using an example of risk of infection in SLE patients with hypogammaglobulinemia.

Keywords: balancing score; observational; propensity score; selection bias.

Publication types

Research Support, Non-U.S. Gov't
Review

MeSH terms

Bias
Humans
Lupus Erythematosus, Systemic* / complications
Lupus Erythematosus, Systemic* / drug therapy
Observational Studies as Topic
Propensity Score
Rare Diseases*
Risk Factors

Grants and funding

CIHR/Canada