RESEARCH - Concordant and discordant association between RA, SLE and AS based on hospitalizations in Sweden between 1973 and 2004

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Rheumatology Advance Access published online on June 4, 2008

Rheumatology, doi:10.1093/rheumatology/ken184

Concordant and discordant associations between rheumatoid arthritis,

systemic lupus erythematosus and ankylosing spondylitis based on all

hospitalizations in Sweden between 1973 and 2004

K. Sundquist1, J. C. eus2, X. Li1, K. Hemminki1,3 and J. Sundquist1

1Center for Family and Community Medicine, Karolinska Institute,

Huddinge, 2The Rheumatologic Clinic, University Hospital, Stockholm,

Sweden and 3Division of Molecular Genetic Epidemiology, German Cancer

Research Center (DKFZ), Heidelberg, Germany.

Abstract

Objectives. To quantify the sibling risk of RA, SLE and AS. To analyse

the concordant and discordant associations between RA, SLE and AS.

Methods. Follow-up study of all individuals and their siblings born in

or after 1932 and hospitalized for RA, SLE or AS between 1973 and 2004

(32 yrs). Data were retrieved from a comprehensive database

constructed by using several national Swedish data registers,

including the Total Population Register, the Swedish Hospital

Discharge Register and the Multigeneration Register. Standardized

incidence ratios (SIRs) were used to estimate sibling risks.

Results. For males, the overall significant SIRs were 4.72, 4.35 and

4.14 for RA, SLE and AS, respectively, if a sibling was affected by

any inflammatory disease. The corresponding significant SIRs for

females were 4.12, 3.73 and 4.73. The concordant significant SIRs in

siblings were 5.12, 17.02 and 17.14 for RA, SLE and AS, respectively.

There were also discordant associations between RA and SLE, whereas AS

was only associated with AS.

Conclusions. This study was able objectively to quantify the sibling

risk of RA, SLE and AS, which represents useful knowledge for

clinicians and geneticists. The analysis of concordant and discordant

associations may be useful in future studies aimed at finding specific

genes associated with these diseases.

http://rheumatology.oxfordjournals.org/cgi/content/abstract/ken184v1?papetoc

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