Motion Analysis Shows That Auto-Injectors Can Be Used by Patients With Varying Degrees of Disability

While injectable drugs, including some innovator anti—tumor necrosis factor inhibitors and their biosimilars, have revolutionized the treatment of rheumatic diseases like rheumatoid arthritis (RA), hand disability can limit the ability of patients with RA to use syringes to administer medication. Prefilled, disposable auto-injectors may help to alleviate this issue and have demonstrated acceptability studies, but questions have remained about whether patients with reduced manual dexterity may still experience needle displacement when using these devices.

A study newly published in Patient Preference and Adherence reports on researchers’ efforts to track the motions of 29 patients with RA who had varying degrees of disability and 9 volunteers without RA as they administered injections to measure the performance of simulated self-injection.

Each individual was asked to perform 2 simulated subcutaneous self-injections using a foam pad attached to a common injection site (1 on the thigh and 1 on the abdomen). Motion was tracked with an electromagnetic motion capture system to track the positions and orientations of the injector and pad. The individuals were given instructions on how to administer the injection, and motion data were streamed and exported for analysis.

In assessing needle displacement in injections, the authors say that, while there were differences between the RA group and the non-RA group in terms of needle displacement, these differences did not reach statistical significance. However, in both groups, injections performed on the abdomen had larger needle displacement than the injections performed on thigh (P = .025). Approximately 60% of patients reached the 90th percentile of their personal displacement within the first 15 seconds of the injection, with little variation over longer injections.

The mean percentage of correctly executed steps for administering the injection was 96.05% for the first injection and 98.02% for the second injection for both groups. In the RA group, the mean percentages were 95.69% and 98.71%.

The authors say that the percentage of patients who successfully handled the auto-injector suggests that the system is easy to use, even for patients with limited dexterity due to RA.

Reference

Xiao X, Li W, Clawson C, Karvani D, Sondag P, Hahn JK. Evaluation of performance, acceptance, and compliance of an auto-injector in healthy and rheumatoid arthritic subjects measured by a motion capture system. Patient Prefer Adherence. 2018; 12:515-526. doi: 10.2147/PPA.S160394.