Development of the Treatment Inventory of Costs in Psychiatric Patients: TIC-P Mini and Midi.

BACKGROUND Medical costs of (psychiatric) illness can be validly measured with patient report questionnaires. These questionnaires comprise many detailed items resulting in lengthy administrations. OBJECTIVES We set out to find the minimal number of items needed to retrieve 80% and 90% of the costs as measured by the Treatment Inventory of Costs in Patients with psychiatric disorders (TIC-P). METHODS The TIC-P is a validated patient-reported outcome measure concerning the utilization of medical care and productivity losses. The present study focused on direct medical costs. We applied data of 7756 TIC-P administrations from three studies in patients with mental health care issues. Items that contribute least to the total cost were eliminated, providing that 80% and 90% of the total cost was retained. RESULTS Average medical costs per patient were €658 over the last 4 weeks. The distribution of cost was highly skewed, and 5 of the 14 items of the TIC-P accounted for less than 10% of the total costs. The 80% Mini version of the TIC-P required five items: ambulatory services, private practice, day care, general hospital, and psychiatric clinic. The TIC-P Midi 90% inventory required eight items. Both had variance between the three samples in the optimal choice of the items. CONCLUSIONS The number of items of the TIC-P can be reduced considerably while maintaining 80% and 90% of the medical costs estimated by the complete TIC-P. The reduced length makes the questionnaire more suitable for routine outcome monitoring.