Evaluation of performance, acceptance, and compliance of an auto-injector in healthy and rheumatoid arthritic subjects measured by a motion capture system

Figures & data

Table 1 Observation steps

Category	Steps	Injection(s)
Injection procedure	S1. Grasp device relative to injection site with one hand S2. Use the other hand to remove cap S3. Make sure that the viewing window is in your line of sight S4. Position the device at a 90° angle against the skin of the injection site S5. Push auto-injector against the injection site until start click occurs S6. Monitor injection progress and wait for end of injection S7. Hold the device in place for at least 60 seconds S8. Remove auto-injector from injection site in a perpendicular position	Injections 1 and 2

Figure 1 Experimental setup with the injection device.

Figure 2 Virtual fiducials used for calibration.

Table 2 Survey questionnaire

Category	Questions	Responses	Injection(s)
Injection evaluation	Q1. On a scale of 1–5, where 1 is not at all confident and 5 is very confident, please rate how confident you are that you administered the injection successfully?	Scale from 1 (not at all confident) to 5 (very confident)	Injections 1 and 2
	Q2. On a scale of 1–5, where 1 is very difficult and 5 is very easy, how would you rate the ease of performing an injection?	Scale from 1 (very difficult) to 5 (very easy)
	Q3. Was there anything about the injection process that caused you to be concerned or to hesitate or that made you feel like you were just about to make a mistake?	Yes/no
	Q4. Imagine a time in the past when the arthritis in your hands has been exceptionally painful. Do you think you would have been able to perform the injection if you had been feeling that way today?	Yes/no	Injections 1 and 2 (RA only)
Auto-injector experience	Q5. On a scale of 1–5, where 1 is very difficult and 5 is very easy, how easy was it to remove the cap of the auto-injector?	Scale from 1 (very difficult) to 5 (very easy)	Injection 2
	Q5.a. In your opinion, was this amount of ease to remove the cap acceptable or unacceptable?	Acceptable/unacceptable
	Q6. On a scale of 1–5, where 1 is very difficult and 5 is very easy, how easy was it to press down on the auto-injector?	Scale from 1 (very difficult) to 5 (very easy)
	Q6.a. In your opinion, was this amount of ease to press down on the auto-injector in place acceptable or unacceptable?	Acceptable/unacceptable
	Q7. On a scare of 1–5, where 1 is very difficult and 5 is very easy, how easy was it to hold the auto-injector in place for the duration of the injection?	Scale from 1 (very difficult) to 5 (very easy)
	Q7.a. In your opinion, was this amount of ease to hold the auto-injector in place acceptable or unacceptable?	Acceptable/unacceptable
	Q8. On a scale of 1–5, where 1 is very difficult and 5 is very easy, how easy was it to grip the auto-injector?	Scale from 1 (very difficult) to 5 (very easy)
	Q8.a. In your opinion, was this amount of ease to grip the auto-injector acceptable or unacceptable?	Acceptable/unacceptable

Abbreviation: RA, rheumatoid arthritics.

Figure 3 The state of the auto-injector when fully inserted into skin.

Figure 4 An illustration for calculating the needle displacements of the entry point and the tip point (d_e, d_t) from the initial pose (p_e, p_t) to the adjusted current pose (p_e″, p_t″). (p_e′, p_t′) is the original current pose.

Figure 5 Comparison of max needle displacement between the healthy group and the RA group based on thigh and abdomen measurements.

Abbreviation: RA, rheumatoid arthritics.

Figure 6 Comparison of mean needle displacement between the healthy group and the RA group based on thigh and abdomen measurements.

Abbreviation: RA, rheumatoid arthritics.

Figure 7 Comparison of SD of needle displacement between the healthy group and the RA group based on thigh and abdomen measurements.

Abbreviation: RA, rheumatoid arthritics.

Figure 8 Comparison of mean needle displacements between subgroups in RA subjects.

Abbreviation: RA, rheumatoid arthritics.

Figure 9 Comparison of mean needle displacement with or without gloves.

Abbreviation: RA, rheumatoid arthritics.

Figure 10 Needle displacement at every 1/60 second for each subject, split by injection site.

Notes: Black curves represent healthy subjects, and colored curves represent RA subjects. The color scale (blue to red) indicates the severity of the disease (low to high).
Abbreviation: RA, rheumatoid arthritics.

Figure 11 Maximum distance reached up to time t.

Notes: The vertical line is t=15 seconds. Blue curves represent healthy subjects, and red curves represent RA subjects.
Abbreviation: RA, rheumatoid arthritics.

Table 3 Percentage of subjects who reached a given percentile of their distance at 15 seconds

Injection site	50th percentile	75th percentile	90th percentile	95th percentile	100th percentile (maximum)
Abdomen	89.19%	78.38%	59.50%	56.76%	32.43%
Thigh	83.78%	67.57%	62.16%	56.76%	29.73%

Figure 12 Maximum distance reached at 15, 30, 45, and 60 seconds per subject.

Note: Healthy subjects are on the left and RA subjects on the right.
Abbreviation: RA, rheumatoid arthritics.

Table 4 Overall device acceptance

Questions	Mean (±SD)/percentage
	Injection 1	Injection 2
Q1	4.53 (±0.92)	4.76 (±0.59)
Q2	4.70 (±0.56)	4.68 (±0.62)
Q3	73.68%	81.58%
Q4	RA only
Q5		3.84 (±1.05)
Q5.a		86.84%
Q6		4.76 (±0.49)
Q6.a		97.37%
Q7		4.29 (±0.96)
Q7.a		89.47%
Q8		4.59 (±0.77)
Q8.a		94.74%

Abbreviation: RA, rheumatoid arthritics.

Table 5 Device acceptance in RA group

Questions	Mean (±SD)/percentage
	Injection 1	Injection 2
Q1	4.48 (±0.91)	4.72 (±0.65)
Q2	4.62 (±0.62)	4.62 (±0.68)
Q3	68.97%	79.31%
Q4	82.75%	89.66%
Q5		3.90 (±1.05)
Q5.a		82.76%
Q6		4.76 (±0.51)
Q6.a		96.55%
Q7		4.21 (±1.02)
Q7.a		86.21%
Q8		4.50 (±0.85)
Q8.a		93.10%

Abbreviation: RA, rheumatoid arthritics.