Negative association between smoking and anti-saccharomyces cerevisiae anti- bodies in Crohn's disease

Background : Crohn's disease (CD) is a polygenic multifactorial heterogeneous disease. Anti-Saccharomyces Cerevisiae antibodies (ASCA) correlate highly with CD and are present in 50-80% of patients. The reason for ASCA positivity or negativity in CD is unknown. The aim of our work was to analyse clinical, epidemio- logical and genetic characteristics in ASCA + or ASCA- CD patients. Methods : 113 patients with CD were tested for ASCA (IgA and IgG) by using a commercial kit (Medipan Diagnostica). Age, gen- der, systemic manifestations, familial form of disease, age at diag- nosis, location and behaviour of the disease, smoking habit as well as genotyping for -308 TNF gene polymorphisms were determi- ned. Results : 38.9% CD patients were negative for both IgA and IgG ASCA while 61.1% were ASCA positive (respectively IgA and IgG : 31.9% ; IgA only : 9.7% ; IgG only : 19.5%). The only sig- nificant difference between ASCA+ and ASCA- patients was for smoking habit : there were 29% smokers in ASCA+ versus 50% in ASCA - CD patients (P = 0.03). This low proportion of smokers was more prominent in ASCA IgA+ patients than in isolated ASCA IgG+ patients (25.6% versus 45.5%) and was minimal in patients with high titers of ASCA IgA (0/8). Logistic regression showed smoking habit still borderline for significance (P = 0.057). Conclusions: Our results suggest a negative association between smoking and ASCA positivity in CD. This association was more prominent for ASCA IgA+. It indicates that smoking habit should be taken into account when analysing ASCA status in CD patients and may suggest an influence of smoking on immuniza- tion against intestinal material. (Acta gastroenterol. belg., 2003, 66, 1-6).