Table 1.
Baseline characteristics of unmatched and matched new-user cohorts of levothyroxine
| Pre-match |
Post-match |
|||||
|---|---|---|---|---|---|---|
| Characteristics | Generic T4 (N = 157,830) | Brand T4 (N = 37,216) | Standardized mean difference | Generic T4 (N = 35,667) | Brand T4 (N = 35,667) | Standardized mean difference |
|
| ||||||
| Initiating dose, μg/d | ||||||
| Mean (SD) | 61.3 (38.8) | 72.2 (42.8) | 0.27 | 70.4 (43.4) | 70.6 (41.8) | 0.00 |
| Median | 50.0 | 50.0 | 50.0 | 50.0 | ||
| TSH level, mIU/L | ||||||
| <0.3 | 5531 (3.5%) | 2326 (6.3%) | 0.13 | 1972 (5.5%) | 2005 (5.6%) | 0.00 |
| 0.3–4.4 | 55,858 (35.4%) | 17,778 (47.8%) | 0.25 | 16,864 (47.3%) | 16,757 (47.0%) | 0.01 |
| 4.5–9.9 | 77,699 (49.2%) | 13,549 (36.4%) | 0.26 | 13,420 (37.6%) | 13,410 (37.6%) | 0.00 |
| 10–19.9 | 10,811 (6.8%) | 1923 (5.2%) | 0.07 | 1843 (5.2%) | 1902 (5.3%) | 0.01 |
| >19.9 | 7931 (5.0%) | 1640 (4.4%) | 0.03 | 1568 (4.4%) | 1593 (4.5%) | 0.00 |
| Age group, y | ||||||
| <35 | 30,419 (19.3%) | 7477 (20.1%) | 0.02 | 7335 (20.6%) | 7169 (20.1%) | 0.01 |
| 35–44 | 33,649 (21.3%) | 8621 (23.2%) | 0.04 | 8369 (23.5%) | 8199 (23.0%) | 0.01 |
| 45–54 | 44,419 (28.1%) | 10,925 (29.4%) | 0.03 | 10,267 (28.8%) | 10,425 (29.2%) | 0.01 |
| 55–64 | 40,747 (25.8%) | 8857 (23.8%) | 0.05 | 8428 (23.6%) | 8559 (24.0%) | 0.01 |
| 65+ | 8596 (5.4%) | 1336 (3.6%) | 0.09 | 1268 (3.6%) | 1315 (3.7%) | 0.01 |
| Gender | ||||||
| Female | 116,083 (73.5%) | 30,157 (81.0%) | 0.18 | 28,889 (81.0%) | 28,762 (80.6%) | 0.01 |
| Male | 41,747 (26.5%) | 7059 (19.0%) | 0.18 | 6778 (19.0%) | 6905 (19.4%) | 0.01 |
| Race/ethnicity | ||||||
| White | 98,726 (62.6%) | 25,232 (67.8%) | 0.11 | 24,126 (67.6%) | 24,007 (67.3%) | 0.01 |
| Black | 17,710 (11.2%) | 3733 (10.0%) | 0.04 | 3584 (10.0%) | 3633 (10.2%) | 0.01 |
| Hispanic | 23,085 (14.6%) | 4347 (11.7%) | 0.09 | 4202 (11.8%) | 4239 (11.9%) | 0.00 |
| Asian | 12,491 (7.9%) | 2449 (6.6%) | 0.05 | 2447 (6.9%) | 2401 (6.7%) | 0.01 |
| Unknown | 5818 (3.7%) | 1455 (3.9%) | 0.01 | 1308 (3.7%) | 1387 (3.9%) | 0.01 |
| Patients census region | ||||||
| Midwest | 17,463 (11.1%) | 3077 (8.3%) | 0.10 | 2902 (8.1%) | 3025 (8.5%) | 0.01 |
| Northeast | 12,895 (8.2%) | 3325 (8.9%) | 0.03 | 3174 (8.9%) | 3185 (8.9%) | 0.00 |
| South | 93,116 (59.0%) | 24,542 (65.9%) | 0.14 | 23,529 (66.0%) | 23,309 (65.4%) | 0.01 |
| West | 34,162 (21.6%) | 6242 (16.8%) | 0.12 | 6027 (16.9%) | 6118 (17.2%) | 0.01 |
| Unknown | 194 (0.1%) | 30 (0.1%) | 0.01 | 35 (0.1%) | 30 (0.1%) | 0.01 |
| Charlson group | ||||||
| 0 | 127,786 (81.0%) | 30,529 (82.0%) | 0.03 | 29,594 (83.0%) | 29,398 (82.4%) | 0.02 |
| 1 | 18,339 (11.6%) | 3843 (10.3%) | 0.04 | 3591 (10.1%) | 3733 (10.50%) | 0.01 |
| 2 | 6699 (4.2%) | 1910 (5.1%) | 0.04 | 1648 (4.6%) | 1659 (4.7%) | 0.00 |
| 3+ | 5006 (3.2%) | 934 (2.5%) | 0.04 | 834 (2.30%) | 877 (2.50%) | 0.00 |
| Household income | ||||||
| <$40,000 | 22,700 (14.4%) | 3434 (9.2%) | 0.16 | 3339 (9.4%) | 3411 (9.6%) | 0.01 |
| $40,000–$74,999 | 37,782 (23.9%) | 7170 (19.3%) | 0.11 | 7014 (19.7%) | 7043 (19.7%) | 0.00 |
| $75,000–$124,999 | 44,218 (28.0%) | 10,273 (27.6%) | 0.01 | 9999 (28.0%) | 9967 (27.9%) | 0.00 |
| $125,000–$199,999 | 25,064 (15.9%) | 7623 (20.5%) | 0.12 | 7199 (20.2%) | 7200 (20.2%) | 0.00 |
| ≥ $200,000 | 16,263 (10.3%) | 6455 (17.3%) | 0.21 | 5934 (16.6%) | 5851 (16.4%) | 0.01 |
| Unknown | 11,803 (7.5%) | 2261 (6.1%) | 0.06 | 2182 (6.1%) | 2195 (6.2%) | 0.00 |
| Year of index prescription | ||||||
| 2008 | 7999 (5.1%) | 3938 (10.6%) | 0.21 | 3519 (9.9%) | 3480 (9.8%) | 0.00 |
| 2009 | 11,520 (7.3%) | 4591 (12.3%) | 0.17 | 4393 (12.3%) | 4225 (11.8%) | 0.01 |
| 2010 | 13,139 (8.3%) | 4777 (12.8%) | 0.15 | 4435 (12.4%) | 4478 (12.6%) | 0.00 |
| 2011 | 12,090 (7.7%) | 3751 (10.1%) | 0.09 | 3501 (9.8%) | 3565 (10.0%) | 0.01 |
| 2012 | 12,529 (7.9%) | 3189 (8.6%) | 0.02 | 3215 (9.0%) | 3116 (8.7%) | 0.01 |
| 2013 | 15,707 (10.0%) | 3661 (9.8%) | 0.00 | 3595 (10.1%) | 3581 (10.0%) | 0.00 |
| 2014 | 14,988 (9.5%) | 2897 (7.8%) | 0.06 | 2960 (8.3%) | 2856 (8.0%) | 0.01 |
| 2015 | 16,706 (10.6%) | 2859 (7.7%) | 0.10 | 2928 (8.2%) | 2835 (7.9%) | 0.01 |
| 2016 | 21,397 (13.6%) | 3224 (8.7%) | 0.16 | 3313 (9.3%) | 3208 (9.0%) | 0.01 |
| 2017 | 18,707 (11.9%) | 2940 (7.9%) | 0.13 | 2552 (7.2%) | 2934 (8.2%) | 0.04 |
| 2018 | 13,048 (8.3%) | 1389 (3.7%) | 0.19 | 1256 (3.5%) | 1389 (3.9%) | 0.02 |
| Prescriber specialty | ||||||
| Endocrinology | 15,193 (9.6%) | 10,770 (28.9%) | 0.51 | 8983 (25.2%) | 9232 (25.9%) | 0.02 |
| Primary care | 96,776 (61.3%) | 18,179 (48.8%) | 0.25 | 18,315 (51.3%) | 18,173 (51.0%) | 0.01 |
| Other | 33,765 (21.4%) | 5902 (15.9%) | 0.14 | 6028 (16.9%) | 5901 (16.5%) | 0.01 |
| Missing/Unknown | 12,096 (7.7%) | 2365 (6.4%) | 0.05 | 2341 (6.6%) | 2361 (6.6%) | 0.00 |
| Baseline conditions | ||||||
| Myocardial infarction | 482 (0.3%) | 67 (0.2%) | 0.03 | 61 (0.2%) | 66 (0.2%) | 0.00 |
| Congestive heart failure | 2407 (1.5%) | 352 (0.9%) | 0.05 | 330 (0.9%) | 345 (1.0%) | 0.00 |
| Peripheral vascular disease | 1962 (1.2%) | 349 (0.9%) | 0.03 | 321 (0.9%) | 337 (0.9%) | 0.01 |
| Cerebrovascular disease | 2093 (1.3%) | 399 (1.1%) | 0.02 | 364 (1.0%) | 390 (1.1%) | 0.01 |
| Cardiac arrhythmia | 7333 (4.6%) | 1527 (4.1%) | 0.03 | 1448 (4.1%) | 1467 (4.1%) | 0.00 |
| Hypothyroidism | 72,057 (45.7%) | 21,931 (58.9%) | 0.27 | 20,592 (57.7%) | 20,606 (57.8%) | 0.00 |
| Hypertension | 45,598 (28.9%) | 8251 (22.2%) | 0.16 | 7861 (22.0%) | 8072 (22.6%) | 0.01 |
| Anemia | 6716 (4.3%) | 1596 (4.3%) | 0.00 | 1522 (4.3%) | 1554 (4.4%) | 0.00 |
| Diabetes | 11,740 (7.4%) | 2286 (6.1%) | 0.05 | 2067 (5.8%) | 2221 (6.2%) | 0.02 |
| Obesity | 17,365 (11.0%) | 2894 (7.8%) | 0.11 | 2668 (7.5%) | 2861 (8.0%) | 0.02 |
| Weight loss | 2053 (1.3%) | 419 (1.1%) | 0.02 | 414 (1.2%) | 411 (1.2%) | 0.00 |
| Depression | 18510 (11.7%) | 4093 (11.0%) | 0.02 | 3861 (10.8%) | 3979 (11.2%) | 0.01 |
| Psychoses | 728 (0.5%) | 131 (0.4%) | 0.02 | 120 (0.3%) | 129 (0.4%) | 0.00 |
| Thyroid cancer | 2125 (1.3%) | 1406 (3.8%) | 0.15 | 1075 (3.0%) | 1033 (2.9%) | 0.01 |
| Paget’s | * | * | 0.00 | * | * | 0.00 |
| Vitamin D deficiency | 19,785 (12.5%) | 5606 (15.1%) | 0.07 | 5190 (14.6%) | 5267 (14.8%) | 0.01 |
| Osteoporosis | 1583 (1.0%) | 450 (1.2%) | 0.02 | 417 (1.2%) | 424 (1.2%) | 0.00 |
| Osteopenia | 3763 (2.4%) | 1387 (3.7%) | 0.08 | 1249 (3.5%) | 1274 (3.6%) | 0.00 |
| Hyperparathyroidism | 489 (0.3%) | 235 (0.6%) | 0.05 | 210 (0.6%) | 193 (0.5%) | 0.01 |
| Cushing’s syndrome | 39 (0.0%) | 13 (0.0%) | 0.01 | 12 (0.0%) | 13 (0.0%) | 0.00 |
| Cirrhosis | 2733 (1.7%) | 496 (1.3%) | 0.03 | 448 (1.3%) | 484 (1.4%) | 0.01 |
| Hypogonadism | 1321 (0.8%) | 188 (0.5%) | 0.04 | 183 (0.5%) | 187 (0.5%) | 0.00 |
| Rheumatoid arthritis | 4686 (3.0%) | 1103 (3.0%) | 0.00 | 1029 (2.9%) | 1063 (3.0%) | 0.01 |
| Menopause | 8510 (5.4%) | 2973 (8.0%) | 0.10 | 2765 (7.8%) | 2774 (7.8%) | 0.00 |
| Alzheimer’s disease | 99 (0.1%) | * | 0.02 | * | * | 0.00 |
| Dementia | 260 (0.2%) | 48 (0.1%) | 0.01 | 38 (0.1%) | 48 (0.1%) | 0.01 |
| Parkinson’s disease | 63 (0.0%) | * | 0.01 | * | * | 0.00 |
| Bulimia or anorexia | 293 (0.2%) | 86 (0.2%) | 0.01 | 76 (0.2%) | 81 (0.2%) | 0.00 |
| Vertebral | 214 (0.1%) | 47 (0.1%) | 0.00 | 40 (0.1%) | 45 (0.1%) | 0.00 |
| Hip | 65 (0.0%) | 16 (0.0%) | 0.00 | 15 (0.0%) | 14 (0.0%) | 0.00 |
| Fracture | 338 (0.2%) | 63 (0.2%) | 0.01 | 60 (0.2%) | 60 (0.2%) | 0.00 |
| Frailty | 2190 (1.4%) | 381 (1.0%) | 0.03 | 336 (0.9%) | 367 (1.0%) | 0.01 |
| Pacemaker device | 657 (0.4%) | 109 (0.3%) | 0.02 | 100 (0.3%) | 106 (0.3%) | 0.00 |
| COPD | 8048 (5.1%) | 1680 (4.5%) | 0.03 | 1586 (4.4%) | 1613 (4.5%) | 0.00 |
| Pneumonia | 2208 (1.4%) | 377 (1.0%) | 0.04 | 346 (1.0%) | 363 (1.0%) | 0.01 |
| Stroke | 1009 (0.6%) | 147 (0.4%) | 0.03 | 123 (0.3%) | 145 (0.4%) | 0.01 |
| Thyroid surgery | 2783 (1.8%) | 1079 (2.9%) | 0.08 | 997 (2.8%) | 971 (2.7%) | 0.00 |
| Medications (180 days prior) | ||||||
| ACEi | 14,066 (8.9%) | 2186 (5.9%) | 0.12 | 2067 (5.8%) | 2154 (6.0%) | 0.01 |
| ARB | 10,110 (6.4%) | 1943 (5.2%) | 0.05 | 1808 (5.1%) | 1882 (5.3%) | 0.01 |
| β-blockers | 12,652 (8.0%) | 2304 (6.2%) | 0.07 | 2210 (6.2%) | 2237 (6.3%) | 0.00 |
| Loop diuretics | 3300 (2.1%) | 486 (1.3%) | 0.06 | 456 (1.3%) | 481 (1.3%) | 0.01 |
| Aldosterone antagonist | 1776 (1.1%) | 404 (1.1%) | 0.00 | 380 (1.1%) | 388 (1.1%) | 0.00 |
| Digoxin | 328 (0.2%) | 61 (0.2%) | 0.01 | 58 (0.2%) | 59 (0.2%) | 0.00 |
| Statin | 21,987 (13.9%) | 4188 (11.3%) | 0.08 | 4019 (11.3%) | 4073 (11.4%) | 0.01 |
| ACEi/ARB | 23,589 (14.9%) | 4024 (10.8%) | 0.12 | 3769 (10.6%) | 3932 (11.0%) | 0.02 |
| Osteoporosis treatment | 14,865 (9.4%) | 3193 (8.6%) | 0.03 | 2992 (8.4%) | 3073 (8.6%) | 0.01 |
| Estrogen | 7124 (4.5%) | 2074 (5.6%) | 0.05 | 1985 (5.6%) | 1980 (5.6%) | 0.00 |
*
Cannot include N when cell size is <11 to protect patient confidentiality