Compliance among patients with schizophrenia is typically poor. Consequently, treatments that are equally efficacious under trial-based conditions but face different compliance rates in clinical practice (e.g. due to adverse-effect profile, ease of use, reputation) may have differences in effectiveness not observed during trials. This study analyses the impact of differences in compliance with atypical antipsychotics using a pharmacoeconomic discrete-event simulation (DES) model, adapted to the Swedish treatment setting.
An existing 5-year DES model was adapted to reflect a Swedish setting; the analysis was conducted from a third-party payer perspective, with only direct costs included. The two treatment arms were identical except for percentage of compliant patients. Non-compliant patients experienced shorter time between relapses and had inferior symptom control than their compliant counterparts. The difference in compliance rates was varied from 0% to 15%, and incremental costs and effects were recorded and analysed.
With a 5%, 10% and 15% difference in compliance rate, incremental effects increased to 0.021, 0.037 and 0.062, respectively, while generating cost savings of Swedish kronor (SEK)31 500, SEK62 000 and SEK104 500, respectively (SEK9.25 = 1, Euro year 2007 values). Hence, each percentage point of compliance gain is predicted to roughly result in a cost saving of SEK6000 and a QALY gain of 0.004. On average, the model predicts that, with a 15% increase in compliance, 0.5 relapses are prevented, the average Positive And Negative Syndrome Scale (PANSS) score decreases by 3.3 points and patients spend 22 fewer days in hospital over 5 years.
The DES model predicts that increases in compliance may lead to considerable cost savings and health improvements. Therefore, when determining the cost effectiveness of a new antipsychotic, efficacy rates from clinical trials should not be taken at face value, but should be interpreted in tandem with expectations concerning compliance, in light of product characteristics such as adverse effects. These results further suggest that efforts to improve compliance among patients with schizophrenia are expected to prove cost effective if compliance gains and the resulting health improvements and cost savings are in balance with the additional costs.