Mapping the relationship between clinical and quality-of-life outcomes in patients with ankylosing spondylitis.
OBJECTIVE
To map health-related quality of life (Qol) with clinical parameters BASFI and ASDAS-CRP measure, and other covariates.


METHODS
Our prospective multicenter non-interventional observation study of ankylosing spondylitis (AS) collected data about QoL and clinical outcomes on the initial and four subsequent visits. We employed simple linear regression analysis of a cross-sectional dataset, and fixed effect, random effect and pooled linear regression of a longitudinal dataset.


RESULTS
We showed that BASFI and ASDAS-CRP are very strong, robust predictors of EQ-5D utilities in all regression specifications together with sex (female), invalidity, and activity impairment. Additionally, the longitudinal regression analysis showed that a fixed effect model may be a viable alternative to the most commonly used random effect model or pooled linear regression due to the nature of our dataset.


CONCLUSIONS
This is one of the first studies using a fixed effect model in longitudinal patient-level data, although, this method has been widely used in economics.
a Institute of Health Economics and Technology Assessment , Prague , Czech Republic.
Tomas
T
Mlcoch
b Institute of Rheumatology , Prague , Czech Republic.|c Clinic of Rheumatology, 1st Faculty of Medicine , Charles University in Prague , Prague , Czech Republic.
Liliana
L
Sedova
b Institute of Rheumatology , Prague , Czech Republic.
Jiri
J
Stolfa
b Institute of Rheumatology , Prague , Czech Republic.
Monika
M
Urbanova
d Department of Clinical Pharmacology, Rheumatology , University Hospital Plzen , Plzen , Czech Republic.
David
D
Suchy
e Third Internal Clinic , University Hospital Olomouc , Olomouc , Czech Republic.
Andrea
A
Smrzova
a Institute of Health Economics and Technology Assessment , Prague , Czech Republic.
Jitka
J
Jircikova
b Institute of Rheumatology , Prague , Czech Republic.
Karel
K
Pavelka
a Institute of Health Economics and Technology Assessment , Prague , Czech Republic.
Tomas
T
Dolezal
D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D011446:Prospective Studies; D011788:Quality of Life; D012720:Severity of Illness Index; D012737:Sex Factors; D013167:Spondylitis, Ankylosing / Q000503:physiopathology*
Ankylosing spondylitis; fixed effect regression; health-related quality of life; longitudinal analysis; mapping; outcomes research; regression analysis