Medical resource utilization in dermatomyositis/polymyositis patients treated with repository corticotropin injection, intravenous immunoglobulin, and/or rituximab

Figures & data

Figure 1 Patient attrition.

Notes: ^aICD-9-CM codes of 710.3 or 710.4. ^bRCI is identified with patients having NDC codes of either 63004-7731-01 or 63004-8710-01 or an HCPCS code for corticotropin injection (J0800).
Abbreviations: RCI, adrenocorticotropic hormone; DM, dermatomyositis; IVIg, intravenous immunoglobulin; PM, polymyositis; ICD-9-CM, International Classifications of Diseases, Ninth Revision, Clinical Modification; NDC, National Drug Codes; HCPCS, Healthcare Common Procedure Coding System.

Table 1 Demographic and pre-index clinical characteristics prior to matching

Characteristic	RCI (N=132)	IVIg (N=1,150)	Rituximab (N=562)	IVIg+ rituximab (N=123)	RCI vs IVIg STDdiff	RCI vs rituximab STDdiff	RCI vs IVIg+ rituximab STDdiff
Age (at index date), mean (SD)	52.6 (11.82)	46.6 (18.43)	51.7 (14.02)	47.8 (15.10)	38.8	6.9	35.7
Female, n (%)	88 (66.7)	796 (69.2)	391 (69.6)	81 (65.9)	5.5	6.2	1.7
Indication of cancer, n (%)	21 (15.9)	256 (22.3)	153 (27.2)	34 (27.6)	16.2	27.7	28.6
Prior DM/PM treatment, n (%)	121 (91.7)	885 (77.0)	516 (91.8)	114 (92.7)	41.2	0.5	3.8
Prior corticosteroids (prednisone or methylprednisolone), n (%)	110 (83.3)	804 (69.9)	502 (89.3)	110 (89.4)	32.1	17.5	17.8
Prior azathioprine, n (%)	38 (28.8)	190 (16.5)	102 (18.1)	30 (24.4)	29.6	25.2	9.9
Prior methotrexate, n (%)	53 (40.2)	385 (33.5)	211 (37.5)	42 (34.1)	13.8	5.3	12.4
Prior MMF, n (%)	29 (22.0)	183 (15.9)	99 (17.6)	29 (23.6)	15.5	10.9	3.8
Deyo’s adapted CCI score, mean (SD)	1.9 (1.58)	1.8 (1.94)	2.2 (2.07)	2.3 (2.45)	8.4	14.0	17.0
Elixhauser Comorbidity Index score (≥2), n (%)	86 (65.2)	617 (53.7)	335 (59.6)	88 (71.5)	23.5	11.4	13.7
Chronic Disease Score, mean (SD)	7.6 (3.78)	5.8 (4.15)	6.5 (4.30)	6.3 (4.35)	44.5	27.2	32.5
Pre-index number of hospitalizations, mean (SD)	2.4 (8.34)	5.1 (13.54)	4.8 (11.47)	7.8 (17.24)	23.7	23.9	39.5
Pre-index total costs (excluding DM/PM medication costs), mean (SD)	35,970 (46,591)	55,195 (92,041)	$42,798 ($75,189)	$71,535 ($119,312)	26.4	10.9	39.3

Abbreviations: CCI, Charlson Comorbidity Index; DM, dermatomyositis; IVIg, intravenous immunoglobulin; MMF, mycophenolate mofetil; PM, polymyositis; RCI, repository corticotropin injection; SD, standard deviation; STDiff, standard difference.

Table 2 Demographic and pre-index clinical characteristics after matching

Characteristica	RCI vs IVIg			RCI vs rituximab			RCI vs IVIg+rituximab
	RCI (N=130)	IVIg (N=390)	STDdiff (%)	RCI (N=110)	Rituximab (N=330)	STDdiff (%)	RCI (N=87)	IVIg+ rituximab (N=87)	STDdiff (%)
Age (at index date), mean (SD)	52.6 (11.81)	52.7 (14.15)	1.4	52.9 (12.26)	52.1 (14.00)	6.1	50.8 (11.91)	50.3 (13.68)	4.4
Female, n (%)	87 (66.9)	257 (65.9)	2.2	75 (68.2)	227 (68.8)	1.3	57 (65.5)	54 (62.1)	7.1
Indication of cancer, n (%)	21 (16.2)	67 (17.2)	2.8	21 (19.1)	65 (19.7)	1.5	19 (21.8)	18 (20.7)	2.8
Prior DM/PM treatment, n (%)	119 (91.5)	347 (89.0)	8.6	102 (92.7)	293 (88.8)	13.6	80 (92.0)	79 (90.8)	4.1
Prior corticosteroids (prednisone or methylprednisolone), n (%)	108 (83.1)	329 (84.4)	3.5	99 (90.0)	287 (87.0)	9.5	74 (85.1)	75 (86.2)	3.3
Prior azathioprine, n (%)	36 (27.7)	92 (23.6)	9.4	25 (22.7)	62 (18.8)	9.7	25 (28.7)	23 (26.4)	5.1
Prior methotrexate, n (%)	52 (40.0)	150 (38.5)	3.1	46 (41.8)	135 (40.9)	1.8	32 (36.8)	33 (37.9)	2.4
Prior MMF, n (%)	28 (21.5)	86 (22.1)	1.2	24 (21.8)	66 (20.0)	4.5	22 (25.3)	20 (23.0)	5.3
Deyo’s adapted CCI score, mean (SD)	1.9 (1.59)	1.8 (1.73)	4.2	2.0 (1.66)	2.0 (1.78)	2.1	1.9 (1.74)	1.8 (1.49)	8.5
Elixhauser Comorbidity Index score (≥2), n (%)	84 (64.6)	253 (64.9)	0.5	69 (62.7)	198 (60.0)	5.6	62 (71.3)	62 (71.3)	0.0
Chronic Disease Score, mean (SD)	7.5 (3.78)	7.2 (4.06)	8.0	7.2 (3.72)	7.1 (4.14)	2.5	7.2 (4.02)	7.0 (4.26)	3.3
Pre-index number of hospitalizations, mean (SD)	2.5 (8.40)	2.5 (4.88)	0.2	2.9 (9.07)	3.2 (6.83)	3.5	3.5 (10.10)	3.4 (7.08)	1.1
Pre-index total costs (excluding	$36,320	$35,203	2.4	$33,487	$34,524	2.3	$43,690	$43,351	0.7
DM/PM medication costs), mean (SD)	($46,852)	($47,225)		($45,898)	($43,409)		($54,525)	($44,265)

Note:

a All variables used in the propensity score matching used to match patients receiving RCI to those not receiving RCI.

Abbreviations: CCI, Charlson Comorbidity Index; DM, dermatomyositis; IVIg, intravenous immunoglobulin; MMF, mycophenolate mofetil; PM, polymyositis; RCI, repository corticotropin injection SD, standard deviation; STDiff, standard difference.

Table 3 Medical resource use in the post-index period

	RCI vs IVIg			RCI vs rituximab			RCI vs IVIg+R
	RCI (N=130)	IVIg (N=390)	P-valuea	RCI (N=110)	Rituximab (N=330)	P-valuea	RCI (N=87)	IVIg+R (N=87)	P-valuea
Hospitalizations
n (%)	26 (20.0)	104 (26.7)		22 (20.0)	101 (30.6)		14 (16.1)	18 (20.7)
Mean PPPM (SD)	0.09 (0.44)	0.17 (0.55)	0.049^*	0.10 (0.48)	0.16 (0.54)	0.128^*	0.08 (0.44)	0.10 (0.44)	0.980^*
LOS, mean (SD)b	3.24 (3.36)	4.55 (9.47)	0.004	2.92 (3.06)	3.09 (3.79)	0.690	2.18 (1.53)	5.15 (8.47)	<0.001^*
ER visits
n (%)	27 (20.8)	95 (24.4)		21 (19.1)	81 (24.6)		14 (16.1)	22 (25.3)
Mean PPPM (SD)	0.04 (0.09)	0.05 (0.15)	0.472	0.03 (0.08)	0.06 (0.19)	0.232^*	0.03 (0.09)	0.06 (0.15)	0.500^*
HOPD visits
n (%)	93 (71.5)	347 (89.0)		78 (70.9)	278 (84.2)		51 (58.6)	76 (87.4)
Mean PPPM (SD)	0.60 (0.92)	1.39 (1.73)	<0.001^*	0.56 (0.89)	0.92 (1.12)	<0.001^*	0.53 (0.93)	1.26 (1.60)	<0.001^*
Physician office visits
n (%)	128 (98.5)	383 (98.2)		108 (98.2)	320 (97.0)		75 (86.2)	86 (98.9)
Mean PPPM (SD)	2.01 (1.73)	2.33 (1.82)	0.035	1.94 (1.64)	2.06 (1.69)	0.473	1.70 (1.82)	2.07 (1.55)	0.589

Notes:

a P-values are from a generalized linear model with Poisson’s distribution and a log link specified. P-values with an asterisk (*) were calculated via a zero-inflated Poisson model due to the presence of >15% observations with a value of 0.

b Among those patients who were hospitalized.

Abbreviations: RCI, repository corticotropin injection; ER, emergency room; HOPD, hospital outpatient department; IVIg, intravenous immunoglobulin; LOS, length of stay; MRU, medical resource utilization; SD, standard deviation; PPPM, per-patient per-month.

Figure 2 Average per-patient per-month total visit costs^a in the post-index period.

Note: ^aExcludes all medications
Abbreviations: PPPM, per-patient per-month; RCI, repository corticotropin injection; IVIg, intravenous immunoglobulin; SD, standard deviation.