An observational, retrospective, UK and Ireland audit of patient adherence to subcutaneous interferon beta-1a injections using the RebiSmart^® injection device

Figures & data

Table 1 Final recorded comfort settings of the RebiSmart^® device (at final injection)

Setting	Patients
Needle speed (default setting, medium)
Fast	99 (44)
Medium	116 (52)
Slow	10 (4)
Injection speed (default setting, medium)
Fast	39 (17)
Medium	127 (56)
Slow	59 (26)
Injection depth (default setting, 10 mm)
10 mm	98 (44)
8 mm	77 (34)
6 mm	45 (20)
4 mm	5 (2)
Injection time (seconds) (default setting, 10 seconds)
Mean (SD)	7.7 (3.8)
Range (min–max)	3–29

Notes: Data shown as n (%) unless indicated otherwise. Percentages may not add up to 100% because of rounding. RebiSmart^® (Merck Serono SA, Geneva, Switzerland).

Abbreviations: SD, standard deviation; min, minimum; max, maximum.

Table 2 Summary of demographics of the full analysis set (n=225)

Characteristic	Patients
Age, years
Mean (SD)	44.1 (8.82)
Median	45.0
Range	23–67
Sex
Male	60 (27)
Female	165 (73)
Location
United Kingdom	161 (72)
Ireland	64 (28)
Prior use of a disease-modifying drug	66 (29)
Interferon β-1a prescription maintenance dose
44 μg	154 (68)
22 μg	71 (32)
Patient registered with Support Linea,b	122 (76)
Patient registered with a field nursea,b	57 (36)
Patient registered with Support Line onlyb
12 months	54 (34)
24 months	62 (39)
Patient registered with a field nurse only (12 or 24 months)b	0
Patient registered with both Support Line and a field nurseb
12 months	56 (35)
24 months	58 (36)
Duration of MySupport registration with Support Line over first 12 months, daysb
Mean (SD)	347.0 (48.16)
Median	364.0
Range	151–364
Duration of MySupport registration with both Support Line and field nurse over first 12 months, daysb
Mean (SD)	321.6 (84.25)
Median	364.0
Range	6–364
Duration of MySupport registration with Support Line over 24 months, daysb
Mean (SD)	620.2 (214.40)
Median	728.0
Range	33–728
Duration of MySupport registration with both Support Line and field nurse over 24 months, daysb
Mean (SD)	666.7 (130.94)
Median	728.0
Range	100–728

Notes: Data are n (%) unless otherwise indicated.

a Registered at any time

b patients in the United Kingdom only.

Abbreviation: SD, standard deviation.

Figure 1 Box and whisker plot of percentage adherence: full analysis set over 1, 3, 6, 12, and 24 months (n=225 at all time points).

Note: *Indicates the mean; horizontal lines, the median.

Table 3 MPR and percentage adherence of UK-based patients with multiple sclerosis at 12 and 24 months (n=161)

Summary statistics	12 months		24 months
	MPRa	Percentage adherenceb	MPRa	Percentage adherenceb
Mean (SD)	102.93 (8.50)	96.05 (9.52)	98.75 (5.93)	95.35 (9.65)
95% CI	101.60–104.25	94.57–97.53	97.83–99.67	93.84–96.85
Median	103.85	99.36	100.00	99.36
Q1, Q3	100.00, 107.69	96.79, 100.00	96.15, 101.92	95.51, 100.00
Min, Max	34.6, 134.6	39.7, 105.8	67.3, 111.5	41.7, 102.2

Notes:

a Patient MPR is calculated as (total number of injections dispensed over 12 or 24 months/scheduled number of injections to be dispensed over 12 or 24 months) ×100%. Note that the MPR can be more than 100% of the scheduled doses, as patients need to keep additional, backup stock of their medication (usually 1 month’s supply)

b percentage adherence is calculated as (number of injections received in time period/number of injections scheduled in time period) ×100%.

Abbreviations: MPR, Medication Possession Ratio; SD, standard deviation; CI, confidence interval; Q, quartile; Min, minimum; Max, maximum.

Table 4 Mean difference between MPR and adherence of UK-based patients with multiple sclerosis at 12 and 24 months (n=161)

Summary statistics	12 months	24 months
Mean difference	6.88	3.41
95% CI	5.29–8.47	1.98–4.83
P-valuea	<0.001	<0.001

Note:

a Paired t-test within patient differences between medication possession ratio and adherence.

Abbreviations: CI, confidence interval; MPR, Medication Possession Ratio.

Table 5 Percentage adherence by subgroup

Subgroup	Mean (SD)	Range	95% CI	P-valuea
Registered to MySupport Support Line only (UK only)
12 months				0.997
Registered (n=54)	96.19 (8.703)	57.1–102.6	93.82–98.57
Not registeredb (n=51)	95.63 (10.556)	39.7–105.8	92.66–98.60
24 months				0.244
Registered (n=62)	95.59 (9.524)	50.6–102.2	93.17–98.01
Not registeredb (n=41)	93.95 (9.726)	66.7–100.6	90.88–97.02
Registered to both Support Line and field nurse (UK only)
12 months				0.579
Registered (n=62)	96.29 (9.424)	47.4–101.9	93.77–98.81
Not registeredb (n=41)	95.63 (10.556)	39.7–105.8	92.66–98.60
24 months				0.092
Registered (n=62)	96.07 (9.798)	41.7–101.3	93.49–98.65
Not registeredb (n=41)	93.95 (9.726)	66.7–100.6	90.88–97.02
Patient age group
12 months				0.099
16–24 years(n=2)	100 (0)	100–100	–
25–39 years (n=64)	93.37 (13.370)	30.8–101.9	–
40–64 years (n=158)	96.08 (10.102)	39.7–105.8	–
≥65 years (n=1)	100 (NC)	100–100	–
24 months				0.126
16–24 years (n=2)	100 (0)	100–100	–
25–39 years (n=64)	92.72 (13.361)	34.9–101.9	–
40–64 years (n=158)	95.89 (9.535)	41.7–105.1	–
≥65 years (n=1)	92.31 (NC)	92.3–92.3	–
Region
12 months				0.905
UK (n=161)	96.05 (9.515)	39.7–105.8	94.57–97.53
Ireland (n=64)	93.63 (14.327)	30.8–103.8	90.05–97.21
24 months				0.379
UK (n=161)	95.35 (9.651)	41.7–102.2	93.84–96.85
Ireland (n=64)	94.17 (13.254)	34.9–105.1	90.86–97.48
sc IFN β-1a prescription maintenance dose
12 months				<0.001
22 μg (n=71)	93.01 (13.124)	34.6–103.8	89.90–96.11
44 μg (n=154)	96.45 (9.919)	30.8–105.8	94.87–98.03
24 months				0.002
22 μg (n=71)	92.43 (12.396)	39.1–102.6	89.50–95.37
44 μg (n=154)	96.20 (9.765)	34.9–105.1	94.64–97.75

Notes:

a Based on a Mann–Whitney U test (except for age, based on Kruskal–Wallis test)

b only patients who were unsupported during the period are included in the category.

Abbreviations: SD, standard deviation; CI, confidence interval; NC, not calculated; sc, subcutaneous; IFN, interferon.