Health care utilization and expenditures among Medicaid beneficiaries with neuropathic pain following spinal cord injury

Figures & data

Table 1 Sample size attrition table

Attrition criterion	N	Percent
At least one spinal cord injury (SCI) diagnosis during January 1, 2006–June 30, 2011	46,931	100.0
Continuous medical and pharmacy benefit enrollment 6 months prior to first SCI diagnosis	19,449	41.4
No SCI diagnosis during the 6 months before the first SCI diagnosis	16,774	35.7
No neuropathic pain (NeP) diagnosis or NeP-related drugs during the 6 months before the first SCI diagnosis	11,705	24.9
NeP diagnosis or NeP-related drug within 12 months following first SCI diagnosis (NeP index event)a	1,603	3.4
Continuous medical and pharmacy benefit enrollment 6 months prior to NeP index event	1,542	3.3
Continuous medical and pharmacy benefit enrollment 12 months following NeP index event	1,116	2.4
No evidence of seizure disorders, multiple sclerosis, amyotrophic lateral sclerosis, diabetic peripheral neuropathy, postherpetic neuralgia, or related medications during pre or postindex periods	708	1.5
Age ≥18 years of age at date of first found SCI event	581	1.2
Patients included in final SCI-NeP cohort after propensity score matching processa	546	1.2

Note:

a Matched patients had no evidence of NeP diagnosis or NeP-related drugs between January 1, 2005 and June 30, 2012, but otherwise the same selection criteria as the matched SCI-NeP patients.

Table 2 Patient demographic characteristics at index date

Variable	SCI-NeP n=546	SCI only n=546	P
Age, years, mean (SD)	40.1 (13.8)	41.5 (16.0)	0.142
Age groups, years, n (%)			0.0004
18–24	103 (18.9)	101 (18.5)
25–34	124 (22.7)	120 (22.0)
35–44	104 (19.0)	76 (13.9)
45–54	128 (23.4)	105 (19.2)
≥55	87 (15.9)	144 (26.4)
Male, n (%)	240 (44.0)	247 (45.2)	0.670
Race, n (%)			0.817
White	320 (58.6)	320 (58.6)
Black	149 (27.3)	158 (28.9)
Other	77 (14.1)	68 (12.5)
Population density, n (%)			0.137
Urban	384 (70.3)	406 (74.4)
Rural	162 (29.7)	140 (25.6)
Insurance plan, n (%)			0.005
Comprehensive	310 (56.8)	305 (55.9)
Health maintenance organization	141 (25.8)	157 (28.8)
Point-of-service	83 (15.2)	84 (15.4)
Other	12 (2.2)	0
Total health care expenditures, mean (SD)a	$48,311 ($108,389)	$38,162 ($89,022)	0.091

Notes:

a For a preindex period of 6 months. The currency used is 2012 US dollars.

Abbreviations: NeP, neuropathic pain; SCI, spinal cord injury; SD, standard deviation.

Table 3 Baseline (preindex) clinical characteristics of the study cohorts

Variable	SCI-NeP n=546	SCI only n=546	P
Type of SCI, %a
Quadriplegia/quadriparesis	20.3	23.8	0.166
Paraplegia	31.1	35.0	0.177
Cauda equina syndrome	10.6	11.5	0.630
Vertebral column fracture	17.0	19.6	0.273
SCI without spinal bone injury	29.1	32.4	0.238
Trauma-related SCIb	30.4	22.3	0.003
Comorbidity indexes, mean (SD)
Deyo-Charlson Comorbidity Index	1.7 (2.0)	1.8 (2.2)	0.420
ICD-9-CM diagnosesc	18.0 (10.7)	17.6 (10.4)	0.466
Outpatient medicationsd	10.2 (8.8)	10.6 (8.4)	0.553
Comorbid conditions, %
Musculoskeletal pain	49.8	50.0	0.952
Gastrointestinal conditionse	36.3	35.5	0.801
Hypertension	32.2	34.1	0.520
Substance abuse	28.2	26.7	0.588
Respiratory conditionsf	22.3	20.9	0.556
Renal/bladder conditionsg	21.4	20.1	0.602
Anxiety	17.4	15.0	0.286
Diabetes	14.3	16.8	0.243
Arthritis (osteoarthritis and rheumatoid arthritis)	12.6	13.6	0.654
Depression	10.8	8.2	0.149
Insomnia/sleep disorders	7.9	7.5	0.820
Atherosclerosis	6.4	6.4	1.000
Deep-vein thrombosis	5.7	4.8	0.496
Medications, %
Opioid analgesics – short-acting	68.5	70.1	0.555
Muscle relaxants	35.9	34.4	0.612
Anxiolytics	34.8	32.4	0.405
NSAIDs	32.6	33.2	0.847
Non-NeP antidepressants	23.8	23.8	1.000
Steroids (systemic)	15.9	15.9	1.000
Sedative/hypnotics	15.8	13.7	0.348
Opioid analgesics – long-acting	11.4	7.7	0.039
Non-NeP antiepileptics	9.5	7.9	0.334
Topical analgesics	4.0	3.8	0.876
SCI- and pain-related procedures, %
Spinal cord surgery	4.6	6.8	0.117
Spine decompression	12.8	7.0	0.001
Stabilization of the spine	10.4	6.2	0.012
Pain intervention procedure	23.8	24.9	0.672

Notes:

a Total proportion exceeds 100% since there is some overlap among the SCI types

b traumatic-SCI was defined as an ICD-9-CM diagnosis code of 806.xx or 907.2x at any time on or after the initial SCI diagnosis

c count of unique three-digit ICD-9-CM codes on medical claims

d count of unique outpatient medications

e gastrointestinal conditions include irritable bowel syndrome, abdominal pain, gastroesophageal reflux disease, ulcers, neurogenic bowel, and constipation

f respiratory conditions include respiratory failure, pulmonary embolism, pneumonia, and chronic obstructive pulmonary disease

g renal/bladder conditions include neurogenic bladder, urinary tract infection, and urinary calculi.

Abbreviations: ICD-9-CM, International Classification of Diseases, Ninth Revision, Clinical Modification; NeP, neuropathic pain; NSAIDs, nonsteroidal anti-inflammatory drugs; SCI, spinal cord injury; SD, standard deviation.

Figure 1 Medication utilization during the 12-month postindex follow-up period.

Note: *P≤0.001 and **P<0.01 versus SCI only.
Abbreviations: NeP, neuropathic pain; NSAIDs, nonsteroidal anti-inflammatory drugs; SCI, spinal cord injury; SD, standard deviation.

Table 4 All-cause, postindex health care resource utilization

Resource type	SCI-NeP n=546	SCI only n=546	P
Inpatient admissions
Patients with any admission, %	34.6	30.6	0.156
Mean (SD) admissions per patient admitted	2.1 (1.8)	2.1 (2.6)	0.989
Mean (SD) length of stay per admission	7.5 (28.7)	4.7 (16.1)	0.050
Emergency department visits
Patients with any visit, %	62.6	56.4	0.036
Mean (SD) visits per patient with visit	4.0 (5.9)	3.6 (4.1)	0.257
Physician office visits
Patients with any visit, %	93.4	87.7	0.001
Mean (SD) visits per patient with visit	11.3 (8.7)	8.3 (7.8)	<0.001
SCI and pain-related procedures
Patients with any visit, %	60.8	47.4	<0.001
Mean (SD) visits per patient with visit	33.9 (59.8)	22.2 (35.9)	0.006
Outpatient drug claims
Patients with any drug claim, %	100	93.0	<0.001
Mean (SD) claims per patient with claim	67.6 (54.2)	50.1 (51.5)	<0.001

Abbreviations: NeP, neuropathic pain; SCI, spinal cord injury; SD, standard deviation.

Table 5 All-cause, postindex health care expenditures

Resource type	SCI-NeP (n=546)		SCI only (n=546)		Pa
	Mean (SD)	Median	Mean (SD)	Median
Inpatient admissions, all patients	$18,122 ($55,828)	$0	$13,691 ($42,384)	$0	0.140
Emergency department, all patients	$788 ($2,320)	$201	$598 ($1,217)	$78	0.091
Physician office visits	$643 ($692)	$506	$444 ($513)	$276	<0.001
SCI- and pain-related outpatient services	$3,543 ($9,829)	$129	$1,702 ($5,703)	$0	<0.001
Total outpatient medical expendituresb	$14,777 ($18,856)	$7,706	$14,218 ($22,424)	$5,000	0.656
Outpatient prescriptions	$4,433 ($6,248)	$2,292	$3,276 ($6,357)	$938	0.002
Total health care expendituresc	$37,333 ($64,334)	$15,411	$31,186 ($52,252)	$11,477	0.083

Notes:

a P-value is for difference in means between SCI-NeP and SCI only

b includes emergency department visits, physician office visits, diagnostic testing, outpatient surgical procedures, and all other outpatient services

c total of inpatient admissions, outpatient medical expenditures, and outpatient prescriptions. The currency used is 2012 US dollars.

Abbreviations: NeP, neuropathic pain; SCI, spinal cord injury; SD, standard deviation.