Unexpected scarring following use of capillary self-blood collection device: A case report and discussion of device design.

Self-administered capillary blood collection devices are increasingly used in both clinical research and patient care. The Tasso+ device, a CE-certified system designed to collect 500 µL of whole blood, is generally regarded as safe and user-friendly. However, complications related to its use remain insufficiently documented. We describe the case of a female study participant who developed an unexpected wound complication after using the self-blood collection device. Although the blood collection itself was successful, the participant later required surgical treatment for a gaping lesion at the application site, which ultimately left a small permanent scar. To our knowledge, this represents a previously unreported adverse effect of the device. The case raises concerns about the interaction between device application and skin tension lines and underscores the need for further evaluation of safety aspects in self-administered blood collection systems.