Background At least grade 2 unilateral sacroiliitis in the presence of spinal symptoms (defined as a combination of inflammatory back pain plus back stiffness) in our criteria allows to classify axial psoriatic arthritis (axPsA). However it is unknown to what extent this sacroiliac involvement is specific for axPsA.
Objectives To determine the prevalence of at least grade II unilateral radiological sacroiliitis in the general population, cutaneous psoriasis and PsA.
Methods Descriptive cross sectional study of 3 cohorts: a) general population: consecutive digitalized pelvis x ray films taken from patients that acceded to the emergency room of the Complejo Hospitalario Universitario La Coruña (CHUAC) between January-March 2010 for spinal pain (1174 x-rays out of 928 patients, 621 patients met inclusion criteria for the analysis), b) patients of a follow up cohort of cutaneous psoriasis (Ps) (n=106), c) PsA patients from CHUAC (n=168) and Complejo Hospitalario Universitario de Orense (CHOU) (n=89). X ray films were red independently by two expert’s rheumatologist, x ray films were discarded if: absence of vision of both sacroiliac joints, blurred x rays, age <18 years old, prosthesis, dysplasia, Paget’s disease and osteitis condensans ilii. If there was a discrepancy consensus was reached between both readers. Prevalence of sacroilitis, together with its 95% confidence interval (CI), was estimated in each cohort. Odds ratio and prevalence ratio values were estimated from a multivariate logistic regression model, adjusted by age and gender.
Results 621 sacroiliac x-rays in the general population, 106 in Ps and 257 in PsA were analysed. Medium age was 58,7±20,1, 54,6±13,1 and 54,6±15,9 years, respectively. The percentage of males in each cohort was 43%, 39,6% y 63%, respectively. Prevalence of at least unilateral grade II sacroiliitis or higher was significantly higher in Ps (16,0%; 95% IC: 8,6%>23,5%) and in PsA (34,2%; 95% IC: 28,2%>40,2%) than in the general population (0,6%; 95% IC: 0,2%>1,6%). Logistic regression analysis showed that the prevalence of sacroiliitis was significantly higher in Ps (OR=35,2; p<0,001) and in PsA (OR=78,6; p<0,001) independently of age and sex. Older age (OR=1,02; p=0,016) and male sex y (OR=4,02; p<0,001) were associated to a higher prevalence of sacroiliitis.
Conclusions The prevalence of at least grade 2 unilateral sacroiliitis or higher was 34,2% in PsA and 16% in Ps, both were higher than in the general population. Prevalence was higher in PsA than in Ps. Prevalence of sacroiliitis increased with age and male gender. These data suggest that the presence of at least grade II unilateral sacroiliitis is specific of PsA and may be used to classify a patient with axial involvement.
Funded with a grant from: Instituto de Salud Carlos III, FIS PI080789
Disclosure of Interest None Declared
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.