Inappropriate prescribing is prevalent in older people. One of the interventions is to optimize geriatric pharmacotherapy with a screening tool to detect potentially inappropriate prescribing. The aim of this study was to develop a novel instrument, the RASP list, which was adapted from The Screening Tool of Older Persons’ potentially inappropriate Prescriptions criteria.

Face validity, usability and time investment were determined. Content validity was verified with the Content Validity Index (CVI) and the modified kappa index (κ*). Cohen's kappa (κ) was used to determine the inter-rater reliability. Content and reproducibility validation were to be repeated if consensus (κ*≥0.74) could not be reached in the first round or if new compelling evidence was published.

Ten experts validated the content of RASP 1.0. The scale-CVI/Average (S-CVI/_Ave) was 0.936, Three items did not reach κ*≥0.74. Median time to complete a patient case with RASP 1.0 was 316seconds. Inter-rater reliability was determined by 9 pharmacists (κ=0.71) and 10 geriatricians (κ=0.63). In a second validation round, 15 items were added to and 3 items deleted from RASP 1.0. Nine experts validated the new content of RASP 2.0. All new items but one reached a κ*≥0.74. The S-CVI/_Ave was 0.923. Inter-rater reliability of RASP 2.0 was performed by 14 pharmacists (κ=0.77). The final version of the RASP list contained 76 items.

The RASP list is a reliable (κ=0.77) and valid (S-CVI/_Ave=0.92) screening tool to identify polypharmacy in older persons. Further research concerning clinical relevancy is warranted.