Andersson et al. BMC Public Health 2011, 11:215 http://www.biomedcentral.com/1471-2458/11/215 Table 2 Mean annual costs Direct medical costs Health care visits Medications Direct non-medical costs Indirect non-medical costs Workloss Work cutback Domestic Total (excl. intervention costs) Intervention costs Total (incl. intervention costs) Annual per capita cost ($) Pre treatment Post treatment CBT(SE) 3,580 (757) 3,444 (756) 136 (19) 1,045 (370) 16,241 (2893) 11,934 (1668) 2,919 (864) 1,388 (301) 20,867 (3395) Control(SE) 3,241 (706) 3,053 (670) 188 (70) 1,086 (498) 10,709 (2308) 6,167 (1295) 3,545 (943) 997 (181) 15,036 (2615) 20,867 (3395) 15,036 (2615) CBT(SE) 3,222 (756) 3,153 (760) 69 (18) 958 (449) 11,227 (2544) 10,086 (2567) 1,097 (292) 921 (225) 15,407 (3048) 1,580 (158) 16,988 (3068) Control(SE) 3,547 (790) 3,323 (746) 225 (73) 571 (305) 12,619 (2482) 9,674 (2505) 2,945 (734) 1102 (300) 16,737 (2713) 135 (26) 16,872 (2720) 3-month follow-up CBT(SE) 2,096 (445) 1,895 (435) 38 (8) 735 (330) 11,324 (2478) 9,561 (2511) 1,262 (323) 500 (117) 14,156 (2660) 1,580 (158) 15,736 (2645) Page 5 of 7 12-month follow-up CBT(SE) 1,754 (450) 1,666 (443) 88 (26) 371 (131) 13,677 (2906) 12,314 (2951) 1,362 (402) 529 (168) 15,802 (3023) 1,580 (158) 17,382 (3038) was statistically significant, Z= 2.64, P < 0.01. The NNT to generate one clinically significant improvement was 2.99 (95%CI 2 to 5), which means that three patients need to receive the intervention to generate one clini- cally significant improvement. At the 3-month follow- up, the fraction of recovered participants in the CBT condition was 14/42 = 0.33, and at one-year follow-up this figure was 18/42 = 0.43. In sum, the effects appear to be sustained over a 12-month period. Cost effectiveness The cost change for the treatment group was 16,988 - 20,867 = -3879. The cost change in the control group was 16,872 - 15,036 = 1835. The incremental cost effectiveness ratio (ICER) was (-3879 - 1835)/(0.36 - 0.02) = -16,806. This means that each significant clinical improvement in IBS is associated with a societal cost-reduction of $16,806. Figure 2 presents the scatter of simulated ICERs across the four quadrants of the ICER plane. If the bulk of simu- lated ICERs appear in the southeast quadrant of the figure, lower costs are associated with a health gain. From a cost- effectiveness perspective, this is the most favorable out- come. If a majority of the simulated ICERs appear in the northwest quadrant, higher costs are associated with a lowered effectiveness, thus making the new intervention unacceptable from a cost-effectiveness perspective. Nearly all simulated ICERs (96%) were located in the southeast quadrant, indicating that the treatment produced benefi- cial effects and reduces costs for society compared to a no treatment control condition. Sensitivity analyses When only including direct medical costs in the estima- tion, 48% of the simulated ICERs were located in the southeast quadrant. When analyzing all data but exclud- ing the unemployment variable, 41% of the dots were located in the southeast quadrant. Data were reanalyzed using regression imputation of missing data instead of last observation carried forward (4 imputations, R- square = 0.93). A majority (98%) of the simulated ICERs were still located in the southeast quadrant, attesting to the robustness of our findings. Finally in order to inves- tigate the long-term impact, we repeated the analyses with follow-up economic data for the treatment group. Using 3-month and 1-year follow-up data, 97% and 89% of the dots were located in the southeast quadrant, respectively. The control group at follow up After the post-treatment the control group was crossed over to treatment. At the 1 year follow-up the group also presented with cost reductions (pre treatment; $15,036, follow-up; $13,008). Additionally 19/43 of the control group participants reported clinically significant symptom relief. Discussion The aim of this study was to determine whether internet- delivered CBT would be a cost-effective or perhaps even a cost-saving intervention for IBS. The results give preli- minary evidence of the internet-delivered treatment as a cost-effective way of offering treatment; better still, our observations suggest that the intervention is cost saving from a societal point of view. Participants in the treat- ment condition demonstrated significant reductions in IBS symptoms compared to the control condition. These improvements were accompanied by cost reductions at post-treatment and at follow-up. While the intervention