Development and validation of the Parotidectomy Outcome Inventory 8 (POI-8). Measurement of quality of life after parotidectomy in benign diseases

To date, no validated instrument for measuring health-related quality of life (QOL) in patients after parotidectomy for benign disease has been available. In our retrospective study we included patients who had undergone parotidectomy for benign disease between 2003 and 2006. A group of experts identified single items with a potential impact on postoperative complaints (alpha version). After the patients had filled out the questionnaire item reduction was performed by sequential statistical analysis. The beta version of the instrument resulting from this procedure was then validated by the evaluation of reliability and validity. We included 199 patients in the study, of which 70 (35%) returned the completed questionnaires. The alpha version of the instrument contained 20 items (Parotidectomy Outcome Inventory-20, POI-20), while the beta version consisted of 8 items (POI-8). Cronbach's alpha was 0.84, indicating good internal consistency. The test-retest reliability score for POI-8 in 49 patients was highly correlated (r=0.91). Furthermore, we found a good concurrent validity with a global disease specific question (r=0.78). The POI-8 is the first reliable and valid instrument for measuring health-related QOL in patients after parotidectomy for benign disease.