The AHRQ Patient Safety Indicators (PSIs) are used to identify patient safety events in acute care settings using administrative data. This retrospective study examined the performance of 16 PSIs across nine hospitals in Switzerland (where the indicators had not been previously applied). The authors attributed low positive predictive value (PPV) in three of the PSIs (pressure injury, falls, and perioperative embolism/thrombosis) to lack of present-on-admission (POA) information, whereas performance of several other indicators were not influenced by missing POA flags.