Table 2.

Demographic and clinical characteristics by biologic treatment pattern. The baseline period is the 6-month continuous timespan preceding the index event of initiation of TNF-α antagonist. TNF-α antagonists are adalimumab, etanercept, and infliximab.

Baseline Characteristics	Single TNF-α Antagonist, N = 2277	Multiple TNF-α Antagonists, N = 231	Non-TNF Biologic DMARD, N = 37
Demographics
Age, yrs, mean (SD)	50.2 (9.1)	50.1 (9.3)	46.9 (11.3)
Female, %	74.1	80.1^**	81.1
Comorbidities
Charlson Comorbidity Index, mean (SD)^{^†}	0.4 (0.8)	0.4 (0.8)	0.8 (1.2)^**
Cancer, %
Lung cancer	0.1	0.0	0.0
Hodgkin’s or non-Hodgkin’s lymphoma	0.2	0.0	2.7^*
Leukemia	0.0	0.0	0.0
Gastrointestinal disease, %
Ulcer	0.6	0.4	2.7
Digestive system disease excluding ulcers and Crohn’s disease	9.7	13.9^**	16.2
Infections, %
Upper respiratory infections	15.2	21.6^***	21.6
Bacterial intestinal infections, bacterial	0.1	1.3^**	2.7^*
Other bacterial infections	1.1	1.7	2.7
Other diseases, %
Diabetes	6.4	6.9	5.4
Fatigue	7.3	10.4^*	13.5
Fibromyalgia	5.7	9.1^**	10.8
Genitourinary disease	22.0	26.8^*	27.0
Major depression	2.6	2.6	5.4
Osteoporosis	11.6	12.6	18.9
Systemic lupus erythematosus	2.8	2.6	13.5^***
Medical services and procedures
Medical services, %
hospital inpatient	7.8	13.0^***	13.5
Rheumatologist office visits	52.3	58.0^*	67.6^*
Bone and joint procedures, %
Arthrocentesis	18.3	22.9^*	16.2
Arthrodesis ever	13.0	16.5	13.5
Arthroplasty	0.8	1.3	2.7
Arthroscopy	1.2	1.3	0.0
Joint aspiration or injection procedures	18.3	22.9^*	16.2
Synovectomy	0.4	0.9	0.0
Joint imaging procedures, %
Bone/joint imaging	1.4	3.9^**	2.7
Hand and wrist radiograph	21.9	28.1^**	29.7
Hip radiograph	3.6	6.1^*	5.4
Other procedures, %
Chest radiograph	25.4	36.4^***	29.7
Prescription drug use, %
≥ 1 outpatient prescription fills for NSAID^††	34.4	38.5	45.9
≥ 1 outpatient prescription fills for opioid analgesic	40.6	51.1^***	62.2^***
Conventional DMARD use, %
≥ 1 prescription fills/administrations of methotrexate	57.8	63.2	56.8
≥ 1 prescription fills/administrations of leflunomide	15.7	22.9^***	27.0^*
Medical service costs in 6-month baseline period, $ mean (SD)
Inpatient	645 (4,596)	1,366 (6,721)^*	3,315 (13,589)
Outpatient, facility	1,169 (3,097)	1,337 (2,666)	1,168 (2,419)
Outpatient, office	1,189 (2,633)	1,366 (2,124)	1,320 (1,668)
Emergency	40 (326)	26 (212)	120 (529)
Other	337 (1,725)	245 (1,133)	912 (4,309)
Total medical service costs	3,380 (7,146)	4,339 (8,417)^**	6,836 (17,188)
Prescription drug costs in 6-month baseline period, $ mean (SD)	1,196 (1,703)	1,392 (1,507)^**	1,519 (1,611)^*

↵† Romano method¹⁴, excluding diagnoses of rheumatoid arthritis.
↵†† Excluding cyclooxygenase-2 inhibitors. Statistical significance at classical thresholds:
↵* 10%;
↵** 5%;
↵*** 1%. TNF-α: tumor necrosis factor-α; DMARD: disease-modifying antirheumatic drug.