Introduction The ACTIB (Assessing Cognitive behavioural Therapy (CBT) for IBS) randomised controlled trial (n=558) was a 3 arm multicentre trial which showed that telephone therapist-delivered CBT (TCBT) and web-based CBT (WCBT) with minimal therapist support were significantly more effective than treatment as usual (TAU) at reducing IBS symptom severity and impact at 12 months in adults with refractory IBS.

Methods A 24 month naturalistic follow-up of ACTIB participants. Participants were recruited from 74 primary care general practice (GP) surgeries and 3 secondary care gastroenterology outpatient clinics in the South of England and London, May 2014 to March 2016. 24 month data collection completed May 2018. TAU participants were given access to the WCBT website from 12 months. Co-primary outcome measures (IBS Symptom Severity Score (IBS SSS) and Work and Social Adjustment Scale (WSAS). Formal trial arm comparisons were Intention-to-treat analyses by multiple imputation to account for missing data.

Results 57.9% (323/558) of participants randomised were followed up to 24 months. Only 10 TAU participants chose to access WCBT.

Preliminary results Compared to TAU (IBS SSS score 198 at 24 months), IBS SSS scores were 40.5 (95% CI (15.0 to 66.0)) points lower (p<0·002) in TCBT and 12.9 (95% CI -12.9 to 38.8) points lower (p=0·3) in WCBT at 24 months. Assessing IBS-SSS responders (participants with a clinically significant IBS SSS change (&x2267;50 point) from baseline to 24 months: 84/119 (70.6%) were responders in TCBT, 62/99 (62.6%) in WCBT and 48/105 (45.7%) in TAU.Compared to TAU (WSAS score 7.6 at 24 months) WSAS was 3.1 (95% CI 1.3 to 4.9) points lower (p<0·001) in TCBT and 1.9 (95% CI 0.1 to 3.7) points lower (p<0·04) in WCBT. Patient enablement (responders): TCBT compared to TAU OR 8.3 (95% CI 4.2 to 16.4) p<0·001), WCBT to TAU OR 3.3 (95% CI 1.8 to 6.0) p=0.001; Hospital anxiety and depression scale (HADS) TCBT to TAU 3.1 (95% CI 1.6 to 4.7) p<0.001 and WCBT to TAU (95% CI 2.7 (1.0 to 4.4) p=0.002.

Conclusions At 24 months sustained benefits were seen in both CBT groups compared to TAU, particularly on impact of IBS symptoms. Some previous gains were reduced compared to 12 month follow-up in the intention-to-treat analysis. Complete case analysis indicated those who had adhered to CBT treatments maintained large clinically significant gains in both symptoms and impact at 24 months. Increasing access to CBT for IBS could achieve long term-benefits for patients