by Kate Cox, Director of Human Factors Engineering
A cornerstone of the Human Factors (HF) process for a medical device FDA submission is delineating which use steps are critical tasks. Often, we get questions from our clients as to what a critical task is and there is some confusion on how we decide what is critical vs non-critical. A common misconception is that a critical task is a step that is necessary to complete in order to operate the device as intended. However, in the world of human factors and usability testing, a critical task is all about the potential harms that could result if the task is performed incorrectly or not at all.
The Center for Devices and Radiologic Health (CDRH) and the Center for Drug Evaluation and Research (CDER) both have a definition for critical tasks that is seemingly the same, but the omission of one word makes a significant difference.
|FDA Division||Critical Task Definition|
|CDRH||A user task which, if performed incorrectly or not performed at all, would or could cause serious harm to the patient or user, where harm is defined to include compromised medical care.|
|CDER||User tasks that, if performed incorrectly or not performed at all, would or could cause harm to the patient or user, where harm is defined to include compromised medical care.|
As noted by CDRH, ‘serious harm’ includes both serious injury and death; where serious injury is defined as “an injury or illness that is life-threatening, results in permanent impairment of a body function or permanent damage to a body structure, or necessitates medical or surgical intervention to preclude permanent impairment of a body function or permanent damage to a body structure. Permanent means irreversible impairment or damage to a body structure or function, excluding trivial impairment or damage”.
The omission of the word ‘serious’ in CDER’s definition denotes that any level of harm or injury that may result is considered as a critical task.
Understanding which of your tasks are critical tasks must be done after you have drafted your use-related risk analysis (URRA) and defined the associated harm and severity for each potential use error.
This oftentimes leads to drug-device combination products having only critical tasks, whereas pure medical devices will vary in the number of Critical vs non-critical tasks.
Based on your device type, be sure to follow the appropriate definition of critical tasks during your HF Validation study and HF submissions!