Anti-saccharomyces cerevisiae antibodies (ASCA) in Crohn's disease: Stability over time and correlation with clinical characteristics

Abstract

Background and Aims:ASCA is a serologic marker that may help in the diagnosis of Crohn's disease(CD) with a sensitivity of 60-70%. The value of serial ASCA measurements in CD is unclear. We assessed the stability of ASCA in CD patients followed prospectively with repeated measures during a 1 year period. The relationship of ASCA with various clinical characteristics was also evaluated. Methods: 78 CD patients in remission had ASCA measured every 3 months up to 1 year or earlier if they relapsed. ASCA was measured using the QUANTA Lite kit (lgA,IgG) (Inova diagnostics, San Diego). Serum values were interpreted using cut-offs provided by the manufacturer ( 25 =positive). ASCA was also measured at 1 timepoint in 70 non-lBD healthy controls. Relapse was defined as a CDAI> 150 with a 70 point increase from baseline The association of ASCA with: age, age at diagnosis, gender, smoking status, disease site and duration, extraintestinal symptoms and immunosuppressant use was assessed by multivariate analylsis. Results: At baseline, 45 patients were ASCA + compared to 8 ASCA + controls (p = <0.001). 2 patients and 3 controls were ASCA equivocal. The sensitivity and specificity of ASCA for CD was 60% and 88% respectively (excluding equivocals). 44 patients remained in remission at 1 year and 34 relapsed. In non-relapsers with 4 or 5 measurements (n = 42), 83% (95% C1, 70-92%) maintained the same ASCA (+ or -) throughout the year. In relapsers, with 4 or 5 measurements (n= 14), 64 % (95%C1, 38-86%) remained unchanged. Overall, ASCA status remained unchanged in 79% (n =44)(95%C1,66-88%) of patients with 4 or 5 measurements. In patients with equivocal ASCA (n = 19) at some timepoint, 47%(95%CI,2769%) remained equivocal, 37% (95%CI,18-60%) became negative and 16% (95%CI,4-37%) changed to positive at next measurement. No relapsers who were ASCA at baseline remission converted to AgCA + at relapse. Also, mean lgA and IgG levels decreased from the remission state to relapse (IgA, 37 to 29, p= 0.04 ; lgG, 45 to 34, p =0.01 ). When assessing clinical factors an association between ASCA and older age at diagnosis (p=0.03) was found. Conclusion: This study demonstrates that ASCA is a stable marker when measured over a 1 year period and only few patients switch ASCA status regardless of disease activity.Therefore,repeatmg measurements in view of increasing the yield of a positive result is likely of little benefit. Also, ASCA was associated with older age at diagnosis.