Ergonomic dialing torque may enhance safety and comfort when setting doses with insulin pens. Limited data are available on the correlation of dialing torque and dialing comfort.
Three studies were performed with SoloSTAR ® (SS; Sanofi), FlexPen ® (FP; Novo Nordisk), KwikPen ® (KP; Eli Lilly) and FlexTouch ® (FT; Novo Nordisk) pens. Dialing behavior was examined with 20 pen-experienced people with diabetes. Participants dialed up to the maximum dose and back down to “zero” with each pen. Hand and pen movements were recorded by video camera and rotational speeds and angles calculated for each pen. In a laboratory study, dialing torque was measured discontinuously at a speed of 120°/s, reflecting typical patient behavior. Sixteen pen-experienced people with diabetes participated in a pilot preference study. Using a Likert scale, subjective dialing comfort rankings and ratings were obtained for each pen type and matched to their dialing torque. SS, FP, KP, and FT1 were investigated at 0–20 U each and at 60–80 U for FT2.
SS was ranked most comfortable for up-dialing by 8 and down-dialing by 6 of the 16 participants, respectively; FP, 5 and 8; FT1, 2 and 1; and KP, 1 and 1. FT2 was ranked least comfortable by 12 and 10 participants. Comfort for up- and down-dialing was rated “very comfortable” for SS by 15 participants each, followed by FP (12 and 14), KP (10 each), and FT1 (9 and 7); FT2 was rated “less” or “not” comfortable by 10 and 11 people, respectively.
In this pilot study, subjective ratings of dialing comfort for different insulin pens by participants appear to concur with previous laboratory dialing torque study results. There appears to be a “torque comfort zone.” Torques above 50 N mm reduced subjective handling comfort. Further, larger scale studies are needed to establish that dialing torque affects pen users’ comfort.