Accurate and reliable detection and measurement of adverse events remains challenging. This systematic review examined the difference in adverse events detected using the Global Trigger Tool compared to those detected via incident reporting systems. In 12 of the 14 included studies, less than 10% of adverse events detected using the Global Trigger Tool were also found in corresponding incident reporting systems. The authors of the review emphasize the importance of using multiple approaches and sources of patient safety data to enhance adverse event detection.