In recent years, our human factors researchers have seen a few persistent use errors in usability studies that involve injection pens. Many home users—patients and caregivers—encounter confusion when interacting with the shields covering the disposable needles that are attached to the pens. One error in particular is severe and prevalent enough to have raised the FDA’s concern. To address it, they have issued a labeling change request to manufacturers.
Most of these home-use pen needles come with two shields: a tiny inner shield that loosely covers the needle itself and an outer shield that maintains sterility and affords a way to attach, remove and dispose of the used needle when finished.
While simple in design, the process of using them is not. Users must use the outer shield to attach the needle, remove the outer shield, remove the inner shield, prime the needle by pushing a few units of insulin through it, reattach the outer shield, prep the injection site, dial the dose, remove the outer shield again, inject, reattach the outer shield again, detach the needle from the pen, and dispose.
Human factors professionals know that this type of process is ideal for use errors—it contains many discrete, redundant steps that must occur in a precise order across tasks that are moving a user’s attention back and forth repeatedly between the various components of the interface and their bodies. In these conditions, steps can be skipped, either by mistake or through a user’s attempt to find workarounds.
The error in question occurs when a user does not remove the inner needle shield, then performs the “injection” without realizing that the tiny needle never entered the skin (which they very rarely feel anyway). He or she comes away assuming the injection was successful but in the case of someone who uses an insulin pen, these failed injections can cause a dangerous rise in blood sugar levels. The FDA has identified at least one death due to hyperglycemia that was related to this error.
Consequently, the FDA has issued instructions to manufacturers of pens and pen needles to address the problem. The guidance asks device makers to change the instructions-for-use and labeling on these products, by improving the clarity of these steps and by adding necessary warnings. They have also issued recommendations to healthcare providers to help improve the training that patients receive.