What you don't know can hurt others. A systematic review on calibration of stimulus intensity in pain research.

Abstract: Calibration of pain stimuli is critical in experimental pain research because it makes it possible to adjust stimulus intensity to match individual pain sensitivity. Despite its importance, precise descriptions of calibration procedures are lacking in the literature, thus hindering the ability to replicate studies. The aim of this systematic review is to fill this gap by evaluating and categorizing calibration methods used in pain studies involving electrodermal stimuli in healthy adult volunteers. A search of 9 databases identified 51 relevant articles published between 2018 and 2024, which were analyzed regarding calibration methods and their effectiveness. The review identified 2 main calibration methods, namely the method of limits and the staircase method, along with 3 techniques, namely ascending, descending, and random calibration. The findings reveal that 69% of studies did not verify the effectiveness of their calibration processes. Among those that did, varying degrees of success were observed. The ascending calibration technique was less precise, while combined ascending and pseudorandom calibration offered better matching of stimulus intensity but still required optimization. However, the data were insufficient to definitively determine which method was the most accurate. There is still a lack of consistent approaches to reporting calibration in the literature, which can lead to difficulties in interpreting results and comparing different studies. Future research should focus on comparing these methods to identify the most effective approaches and explore factors influencing calibration success.