Healthcare costs for Crohn’s disease patients treated with infliximab: a propensity weighted comparison of the effects of treatment adherence

Figures & data

Figure 1. Identification of primary and secondary analysis cohorts.

Table 1. Sample attrition for Crohn’s patients.

Criteria	% Removed*	n Remaining
Include only patients with one or more claims for infliximab billed with a HCPCS code of J1745 between January 1, 2006 and December 31, 2009.	NA	39,593
Number of patients with at least two Crohn’s Disease diagnoses separated by 30 days in the time period of interest.	86.7%	5259
Include only patients that are 18 years of age or greater at index.	11.4%	4661
Include only patients with continuous enrollment for 12 months prior and 12 months after the index date.	52.2%	2230
Exclude patients having any claims with an ICD-9-CM code for rheumatoid arthritis (714.XX).	14.1%	1916
Exclude patients having any claims for infliximab billed with a Pharmacy National Drug Code (NDC).	4.9%	1823
Exclude patients having evidence of another biologic drug any time during the study period (January 2005–December 2010).	21.2%	1437
Exclude patients without pharmacy claims coverage during the 360 days pre- and post-index date.	27.6%	1040
Exclude patients who are hospitalized on index date.	0.2%	1038
Exclude patients with negative paid amounts on claims.	1.9%	945

*Percentages are rounded.

Table 2. Compliance group assignments for patients with Crohn’s disease.

Group	Rules for assignment	n	%
Adherent	Have infliximab therapy for 80% or more of the post period based on dispensing dates and assumed duration of action (14 days for infusion 1, 28 days for infusion 2, and 56 days for all others).	360	38.1
Intermittent	Patients whose first drug exposure date and last exposure date spanned 324 days or more (i.e., 90% of days in the post-index period). These patients were persistent, but not adherent.	239	25.3
Switched or dropped-off	Dropped off therapy or switched to a therapy different from infliximab.	346	36.6
Total		945	100.0

Table 3. Crohn’s disease patient characteristics.

Parameter	Adherent	Intermittently adherent
n	239	360
Age in years at index date
Mean (±SD)	43.4 ± 15.8	42.6 ± 15.3
Gender
Male, n (%)	109 (45.6)	185 (51.4)
Female, n (%)	130 (54.4)	175 (48.6)
Region
Northeast	29 (12.1)	52 (14.4)
North Central	85 (35.6)	106 (29.4)
South	94 (39.3)	150 (41.7)
West	31 (13.0)	51 (14.2)
Unknown	0 (0.0)	1 (0.3)

Table 4. Variables in the logistic regression model used to develop propensity weights whose p-values were ≤0.1.

		Wald 95% CI
Variable	p-value	Lower limit	Odds ratio estimate	Upper limit
Infliximab initiation during 2009 (index year)	0.0228	1.085	1.794	2.966
Male	0.0029	1.269	2.003	3.164
Skin disease diagnosis	0.0387	0.356	0.589	0.973
Supplementary classification diagnoses*	0.0958	0.928	1.529	2.522
Irritable bowel syndrome	0.0854	0.889	2.325	6.081
Office for first infliximab infusion	0.0072	1.413	3.577	9.058
Bowel procedure	0.0324	1.086	2.679	6.606
Outpatient costs (in 10,000 s)	<0.0001	0.322	0.411	0.524
Pharmacy costs (in 10,000 s)	0.0780	0.382	0.634	1.052
Number of outpatient visits (in 1 s)	<0.0001	1.023	1.045	1.068
Number of colonoscopies (in 1 s)	<0.0001	1.784	2.613	3.828

*Supplementary classification codes (i.e., ‘V codes’) include diagnoses such as annual physical, special laboratory examination, and indicators for long-term use of high risk medications.

Table 5. Crohn’s outcomes models using average treatment effect in the treated (ATT) weights derived from propensity scores.

	Adherent (n = 360)			Intermittently adherent (n = 239)
	LS mean	(SE)	95% CI [Low, High]	LS mean	(SE)	95% CI [Low, High]	p-value
All cause
Total costs	$40,425	($907)	[$38,686, $42,242]	$41,082	($1544)	[$38,163, $44,223]	0.7125
Total costs with infliximab removed	$13,097	($506)	[$12,141, $14,127]	$20,068	($1299)	[$17,676, $22,784]	<0.0001
Total infliximab costs	$27,328	($927)	[$25,570, $29,207]	$21,014	($1194)	[$18,798, $23,490]	0.0001
Cost components
Inpatient	$2764	($355)	[$2149, $3,556]	$6665	($1436)	[$4369, $10,165]	0.0002
Outpatient	$34,401	($708)	[$33,041, $35,816]	$31,209	($1076)	[$29,170, $33,391]	0.0163
Outpatient costs with infliximab   removed	$7074	($244)	[$6611, $7569]	$10,196	($590)	[$9103, $11,421]	<0.0001
Outpatient infliximab costs	$27,328	($932)	[$25,561, $29,217]	$21,013	($1200)	[$18,787, $23,503]	0.0001
Emergency room	$303	($31)	[$248, $370]	$357	($61)	[$255, $499]	0.4050
ER costs with infliximab removed	$302	($33)	[$244, $374]	$356	($65)	[$250, $508]	0.4309
ER infliximab costs*	NA		NA	NA		NA	NA
Pharmacy	$2957	($176)	[$2630, $3324]	$2851	($285)	[$2344, $3468]	0.7548
Crohn’s disease-related
Total costs	$33,259	($762)	[$31,798, $34,787]	$32,517	($1249)	[$30,159, $35,059]	0.6145
Total costs with infliximab removed	$5932	($270)	[$5425, $6486]	$11,504	($878)	[$9906, $13,360]	<0.0001
Total infliximab costs	$27,327	($947)	[$25,533, $29,248]	$21,013	($1220)	[$18,753, $23,545]	0.0002
Cost components
Inpatient	$1595	($217)	[$1221, $2084]	$4373	($999)	[$2795, $6841]	<0.0001
Outpatient	$31,419	($667)	[$30,138, $32,754]	$27,909	($993)	[$26,030, $29,925]	0.0047
Outpatient costs with infliximab   removed	$4092	($158)	[$3795, $4413]	$6897	($445)	[$6078, $7828]	<0.0001
Outpatient infliximab costs	$27,327	($947)	[$25,533, $29,248]	$21,013	($1220)	[$18,753, $23,545]	0.0002
Emergency room	$54	($6)	[$44, $66]	$46	($8)	[$33, $65]	0.4556
ER costs with infliximab removed	$53	($6)	[$43, $66]	$45	($9)	[$31, $66]	0.4833
ER infliximab costs*	NA		NA	NA		NA	NA
Pharmacy	$191	($17)	[$160, $229]	$189	($29)	[$140, $254]	0.9356

Propensity weighted Generalized Linear Model using the gamma distribution for costs and a log link, robust variance.

Costs adjusted to December 2010 using the Medical Services of the Consumer Pricing Index16.

*Cost estimates were <$1.

US Department of Labor, Bureau of Labor Statistics. All Urban Consumers, medical services component, Consumer Price Index. Washington D.C., USA http://www.bls.gov. Accessed May 20, 2014

 Google Scholar