Table 1.

Baseline characteristics of levetiracetam users versus nonusers before and post propensity score matching

CharacteristicaBefore MatchingPost Matching
Levetiracetam UsersLevetiracetam NonusersStandardized Differenceb (%)Levetiracetam UsersLevetiracetam NonusersStandardized Differenceb (%)
Total patients, N49801,413,13939807960
Demographics
 Mean age±SD, yr54±2169±167655±2155±210
  ≤65 yr3092 (62)395,028 (28)732403 (60)4878 (61)2
 Women2549 (51)837,046 (59)162048 (52)4013 (50)2
 Long-term care352 (7)52,086 (4)15273 (7)522 (7)1
 Rural residence496 (10)167,640 (12)6409 (10)829 (10)0
 Income quintilec
  1 (lowest)1149 (23)335,883 (24)2958 (24)2009 (25)3
  3 (middle)1002 (20)267,725 (19)3808 (20)1584 (20)1
  5 (highest)897 (18)246,083 (17)2696 (18)1375 (17)1
Comorbiditiesd
 Johns Hopkins ACG System Aggregated Diagnosis Groups, mean±SDe10.0±4.38.2±3.8459.7±4.39.8±4.24
 AKI16 (0.3)2517 (0.2)213 (0.3)21 (0.3)1
 Anxiety disorder and depression881 (18)186,741 (13)12699 (18)1495 (19)4
 Benign brain tumor11 (0.2)219 (0.0)66 (0.2)22 (0.3)3
 Bipolar disorder344 (7)76,931 (5)6280 (7)624 (8)4
 Brain injury220 (4)7274 (0.5)25153 (4)287 (4)2
 Brain cancer329 (7)726 (0.1)37142 (4)167 (2)11
 Cancerf1804 (36)441,339 (31)111333 (34)2621 (33)1
 CKD549 (11)134,314 (10)5432 (11)830 (10)2
 Chronic liver disease361 (7)68,436 (5)10273 (7)598 (8)3
 Coronary artery disease, including anginag1026 (21)382,315 (27)15824 (21)1668 (21)1
 Congestive heart failure451 (9)134,949 (10)1362 (9)774 (10)3
 Diabetes127 (3)49,027 (4)5103 (3)190 (2)2
 Epilepsy/seizureh3481 (70)25,154 (2)2022482 (62)5019 (63)1
  Previous 90 d1087 (22)2772 (0.2)74460 (12)920 (12)0
  Previous 90–365 d1583 (32)6731 (0.5)941091 (27)1984 (25)6
 Hypertension1322 (27)706,449 (50)501095 (28)2148 (27)1
 Migraine618 (12)85,403 (6)22485 (12)987 (12)1
 Mood disorder236 (5)27,938 (2)15174 (4)413 (5)5
 Multiple sclerosis28 (0.6)2612 (0.2)615 (0.4)92 (1)11
 Neuropathic pain67 (1)19,639 (1)147 (1)141 (2)6
 Parkinson disease42 (0.8)6712 (0.5)436 (0.9)136 (2)9
 Peripheral vascular disease54 (1)16,050 (1)045 (1)109 (1)3
 Stroke, including TIA660 (13)36,398 (3)40481 (12)966 (12)0
 Trigeminal neuralgia80 (2)20,422 (1)259 (2)172 (2)6
Concurrent medication usei
 ACE inhibitors or ARBs851 (17)460,963 (33)36706 (18)1362 (17)2
 Antidepressants239 (5)80,146 (6)4199 (5)405 (5)0
 Antiepileptics942 (19)74,430 (5)43703 (18)1562 (20)6
 Antineoplastics176 (4)37,894 (3)5129 (3)234 (3)2
 Antipsychotics190 (4)49,287 (4)2165 (4)332 (4)0
β blockers642 (13)304,371 (22)23518 (13)1046 (13)0
 Benzodiazepines413 (8)149,512 (11)8309 (8)653 (8)2
 Calcium channel blockers556 (11)285,732 (20)25456 (12)899 (11)1
 Glucocorticoids263 (5)51,529 (4)8176 (4)338 (4)1
 Diuretics—potassium sparing58 (1)40,865 (3)1251 (1)98 (1)1
 Diuretics—thiazides225 (5)156,167 (11)25187 (5)318 (4)4
 Diuretics—loop228 (5)102,693 (7)11185 (5)388 (5)1
 Methotrexate20 (0.4)10,269 (0.7)415 (0.4)44 (0.6)3
 NSAIDs (excluding ASA)141 (3)128,727 (9)27117 (3)219 (3)1
 Statins1052 (21)533,226 (38)37886 (22)1757 (22)1
 Number of unique medications, mean±SD3.4±5.04.9±4.6313.4±4.93.4±5.10
Antiepileptic use (in prior 120 d)i
 Carbamazepine162 (3)7476 (0.5)20125 (3)275 (4)2
 Clobazam146 (3)1079 (0.1)2485 (2)159 (2)1
 Divalproex sodium96 (2)5104 (0.4)1567 (2)162 (2)3
 Gabapentin120 (2)26,704 (2)489 (2)267 (3)8
 Lacosamide56 (1)178 (0.0)1537 (0.9)52 (0.7)4
 Lamotrigine115 (2)2248 (0.2)2085 (2)168 (2)0
 Phenytoin426 (9)11,026 (0.8)37291 (7)677 (9)5
 Pregabalin50 (1)21,028 (2)444 (1)105 (1)2
 Primidone27 (0.5)2215 (0.2)722 (0.6)33 (0.4)2
 Topiramate43 (0.9)1887 (0.1)1031 (0.8)62 (0.8)0
 Valproic acid63 (1)2104 (0.1)1346 (1)90 (1)0
Antiepileptic use (prescribed on index date)
 Carbamazepine39 (0.8)355 (0.0)1223 (0.6)34 (0.4)3
 Clobazam43 (0.9)37 (0.0)1313 (0.3)10 (0.1)5
 Divalproex sodium31 (0.6)316 (0.0)1114 (0.4)21 (0.3)2
 Gabapentin41 (0.8)1139 (0.1)1124 (0.6)49 (0.6)0
 Lamotrigine32 (0.6)113 (0.0)1118 (0.5)18 (0.2)5
 Phenytoin108 (2)551 (0.0)2048 (1)76 (1)3
Healthcare contacts, mean±SDj
 Number of primary care physician visits14.9±19.09.7±10.63313.7±17.413.7±16.20
 Number of internal medicine visits3.1±8.50.8±3.0352.4±6.92.3±6.81
 Number of nephrology visits0.2±1.30.1±0.8100.2±1.10.2±1.30
 Number of neurology visits3.8±5.70.2±0.9882.8±4.22.5±3.88
 Number of psychiatry visits0.9±5.60.6±4.171.0±6.11.0±4.91
 Number of hospitalizations1.1±1.60.4±1.0490.9±1.40.9±1.41
 Number of ED visits2.2±3.10.8±1.9541.9±2.81.9±3.22
Healthcare usagek
 Serum creatinine tests3283 (66)1,017,278 (72)132617 (66)5275 (66)1
 CT head2362 (47)143,204 (10)901620 (41)3315 (42)2
 MRI head1781 (36)50,669 (4)891164 (29)2185 (27)5
 Electroencephalography1702 (34)12,678 (0.9)971113 (28)2061 (26)6
 Chest x-ray2413 (49)445,900 (32)351767 (44)3579 (45)1
 Echocardiography1044 (21)240,986 (17)10770 (19)1601 (20)2
 Epilepsy surgery27 (0.5)29 (0.0)1013 (0.3)12 (0.2)4
 Video EEG monitoring365 (7)1578 (0.1)39209 (5)336 (4)6
 Urinalysis1554 (31)555,062 (39)171263 (32)2493 (31)1
Levetiracetam prescriber
 Primary care physician1749 (35)1435 (36)
 Internal medicine74 (2)49 (1)
 Neurology2176 (44)1754 (44)
 Neurosurgery19 (0.4)11 (0.3)
 Psychiatry17 (0.3)15 (0.4)
 Other/missing945 (19)716 (18)
Laboratory data (in subpopulation)
 ≥1 serum creatinine measurement619202,714509 (13)1018 (13)
 Mean serum creatinine level, mg/dl±SD0.83±0.290.93±0.36310.82±0.270.84±0.268
 Median serum creatinine level mg/dl (IQR)0.77 (0.66–0.94)0.86 (0.72–1.04)0.77 (0.66–0.93)0.79 (0.67–0.96)
 Median eGFR, ml/min per 1.73 m2 (IQR)90 (73–105)77 (61–89)91 (74–108)91 (75–105)
 eGFR Category, ml/min per 1.73 m2
  ≥60528 of 619 (85)153,348 of 202,714 (76)1442 of 509 (87)884 of 1018 (87)0
  45–6056 of 619 (9)29,952 of 202,714 (15)842 of 509 (8)84 of 1018 (8)0
  15–4535 of 619 (6)18,907 of 202,714 (9)625 of 509 (5)50 of 1018 (5)0
  <150 of 619 (0)507 of 202,714 (0.3)00 of 509 (0)0 of 1018 (0)0
 Random urine albumin creatinine ratio, mg/g
  <3051 of 75 (68)36,665 of 51,154 (72)1243 of 58 (74)90 of 118 (76)0
  ≥3024 of 75 (32)14,489 of 51,154 (28)815 of 58 (26)28 of 118 (24)0
  • ACG, Adjusted Clinical Group; TIA, transient ischemic attack; ACE inhibitor, angiotensin-converting enzyme inhibitor; ARB, angiotensin II receptor blocker; NSAID, nonsteroidal anti-inflammatory drug; ASA, acetylsalicylic acid; ER, emergency department; CT, computed tomography; MRI, magnetic resonance imaging; EEG, electroencephalogram; —, not applicable; IQR, interquartile range.

  • a Data are presented as the number (percentage) of patients, unless otherwise reported.

  • b Standardized differences are less sensitive to sample size than traditional hypothesis tests are. They provide a measure of the difference between groups with respect to the pooled SD; a standardized difference >10% was considered a meaningful difference between the groups.

  • c Income was categorized into fifths of average neighborhood income on the index date.

  • d Comorbid conditions in the 5 yr preceding the index date were considered.

  • e We used the ACG scoring system to score comorbidity. The ACG is a population/patient case-mix adjustment system that provides a relative measure of the individual’s expected consumption of health services. ICD-9/ICD-9-CM codes are categorized into 32 groups, called Ambulatory Diagnostic Groups, on the basis of clinical similarity, chronicity, likelihood of requiring specialty care, and disability. These groups are further reduced to 12 “Collapsed Ambulatory Diagnostic Groups.”

  • f Cancers include lung/bronchi, colon/rectum, breast, pancreas, prostate, leukemia, non-Hodgkin lymphoma, liver, ovarian, and esophageal.

  • g Coronary artery disease includes receipt of coronary artery bypass graft surgery, and percutaneous coronary intervention.

  • h Epilepsy/seizure codes are hospital diagnosis codes and do not capture those patients who do not present to hospital, which underestimates the prevalence of the condition.

  • i Dispensed medications in the 120 d preceding the index date were considered.

  • j Health care contacts in the year preceding the index date were considered.

  • k Health care use in the year preceding the index date was considered.