Inflammatory bowel disease: healthcare costs for patients who are adherent or non-adherent with infliximab therapy

Figures & data

Table 1. Cost components during the 360 day post-index period for each patient.

Cost component	Description
Total cost	Sum of infliximab drug cost and healthcare cost
Infliximab drug cost	Total drug acquisition cost for infliximab
Healthcare cost	Sum of outpatient, inpatient, pharmaceuticals, and emergency room costs
Outpatient cost	Total cost of outpatient claims*
Inpatient cost	Total cost of inpatient claims*
Pharmaceuticals cost	Total cost of pharmaceutical claims†
Emergency room cost	Total cost of emergency room claims*

*Analyses of disease-related outpatient, inpatient, and emergency room costs included those claims with Crohn’s disease or ulcerative colitis in the primary diagnosis field, a Healthcare Common Procedure Coding System code for infliximab or a code for a bowel procedure (see text for list of bowel procedures included in disease-related costs).

†Analysis of disease-related pharmaceuticals cost included aminosalicylates, azathioprine, corticosteroids, cyclosporin, 6-mercaptopurine, methotrexate, metronidazole, mycophenolate mofetil, or tacrolimus.

Table 2. Sample attrition by diagnosis.

	Crohn’s Disease		Ulcerative Colitis
	Removed	Remaining	Removed	Remaining
Inclusion criteria
≥2 claims with inflammatory bowel disease		5259		2757
≥18 years of age at index	598 (11.4%)	4661	150 (5.4%)	2607
Continuously enrolled* in health plan	2431 (52.2%)	2230	1302 (49.9%)	1305
Exclusion criteria
ICD-9-CM for RA in 2005–2010	314 (14.1%)	1916	171 (13.1%)	1134
NDC for infliximab in 2005–2010	93 (4.9%)	1823	39 (3.4%)	1095
Adalimumab or certolizumab pegol claim in 2005–2010	386 (21.2%)	1437	116 (10.6%)	979
Not continuously enrolled* in pharmacy plan	397 (27.6%)	1040	228 (23.3%)	751
Hospitalized on index date	2 (0.2%)	1038	2 (0.3%)	749
Negative paid amounts on claims	93 (9.0%)	945	48 (6.4%)	701

RA = rheumatoid arthritis; NDC = National Drug Code.

*Continuously enrolled defined as enrollment throughout the 360 day pre-index and 360 day post-index periods.

Table 3. Patient demographics.

	All Patients (n = 1646)	Adherent (n = 674)	Non-adherent (n = 972)
Age (y), mean ± SD	44.4 ± 15.6	43.1 ± 14.9	45.3 ± 15.9
Sex, n (%)
Male	851 (51.7)	355 (52.7)	496 (51.0)
Female	795 (48.3)	319 (47.3)	476 (49.0)
Year of first infliximab claim, n (%)
2006	415 (25.2)	164 (24.3)	251 (25.8)
2007	430 (26.1)	145 (21.5)	285 (29.3)
2008	387 (23.5)	160 (23.7)	227 (23.4)
2009	414 (25.2)	205 (30.4)	209 (21.5)
Health plan, n (%)
Preferred provider organization	875 (53.2)	365 (54.2)	510 (52.5)
Health maintenance organization	281 (17.1)	108 (16.0)	173 (17.8)
Medicare	188 (11.4)	59 (8.8)	129 (13.3)
Point of service, non-capitated	143 (8.7)	76 (11.3)	67 (6.9)
Missing/unknown	24 (1.5)	8 (1.2)	16 (1.6)
Other (each <5%)	135 (8.2)	58 (8.6)	77 (7.9)
Total no. of prescriptions, pre-index
Mean ± SD	32.4 ± 24.3	31.9 ± 22.7	32.7 ± 25.4
Median (range)	27 (0–207)	27 (0–184)	27 (0–207)
Disease-related drugs, % of days available pre-index, mean ± SD*
Aminosalicylate	38.2 ± 32.8	41.7 ± 32.1	35.7 ± 33.0
Corticosteroid	15.2 ± 18.0	16.5 ± 17.9	14.4 ± 18.1
Azathioprine	13.8 ± 26.3	15.2 ± 27.7	12.8 ± 25.2
6-Mercaptopurine	9.3 ± 22.7	8.6 ± 21.5	9.9 ± 23.5
Metronidazole	2.7 ± 7.1	2.7 ± 6.4	2.6 ± 7.5
Ciprofloxacin	1.9 ± 7.9	1.8 ± 8.0	2.0 ± 7.9
All-cause costs pre-index ($US), mean ± SD
Total	22,463 ± 25,376	18,358 ± 23,575	25,310 ± 26,190
Outpatient	10,264 ± 12,489	7121 ± 8205	12,443 ± 14,352
Inpatient	7814 ± 20,092	6878 ± 19,860	8462 ± 20,236
Pharmaceuticals	3903 ± 3747	3936 ± 3125	3880 ± 4126
Emergency room	483 ± 1501	423 ± 958	525 ± 1783
Disease-related costs pre-index ($US), mean ± SD
Total	11,004 ± 17,978	7203 ± 15,961	13,640 ± 18,815
Outpatient	5577 ± 10,777	2306 ± 3218	7845 ± 13,304
Inpatient	5037 ± 14,831	4560 ± 15,474	5368 ± 14,368
Pharmaceuticals	293 ± 686	292 ± 726	294 ± 657
Emergency room	97 ± 806	44 ± 203	133 ± 1034

*Disease-related pharmaceuticals on a mean of <1% of days in both groups were cyclosporin, methotrexate, mycophenolate mofetil, and tacrolimus.

Table 4. Significant variables in the logistic regression model used to develop propensity weights.

Variable	p Value	95% Confidence Interval
		Low	Estimate	High
Age (10 year increment)	0.010	0.798	0.880	0.970
Infliximab initiation in 2009 (index year)	<0.001	1.319	1.686	2.155
Medicare	0.062	0.406	0.645	1.022
Supplementary classification diagnoses*	0.003	1.144	1.493	1.948
Office for first infliximab infusion	0.004	1.264	2.076	3.410
Aminosalicylate (% days available)	0.021	1.001	1.005	1.009
Outpatient costs (per $1000)	<0.001	0.535	0.617	0.710
Number of outpatient visits	0.017	1.002	1.012	1.021
Number of colonoscopies	0.003	1.097	1.307	1.556

*Supplementary classification codes include annual physical, special lab exams, and indicators for long-term use of high-risk medications.

Figure 1. Propensity-weighted mean annual all-cause healthcare costs by adherence status. ER, emergency room. *Cost component was significantly higher (p < 0.001) in the propensity-weighted non-adherent group. †Cost component was significantly higher (p < 0.001) in the adherent group.

Figure 2. Propensity-weighted mean annual disease-related healthcare costs by adherence status. ER, emergency room. *Cost component was significantly higher (p < 0.001) in the propensity-weighted non-adherent group. †Cost component was significantly higher (p < 0.05) in the propensity-weighted non-adherent group. ‡Cost component was significantly higher (p < 0.001) in the adherent group.