Table 1. Baseline Characteristics for Adult Patients Who Continued Taking the Same Sourced Generic Levothyroxine Product or Who Switched.
| Characteristic | Unmatched | 1:1 Matched | ||||
|---|---|---|---|---|---|---|
| No. (%) | SMD | No. (%) | SMD | |||
| Nonswitchers (n = 13 049) | Switchers (n = 2780) | Nonswitchers (n = 2780) | Switchers (n = 2780) | |||
| Levothyroxine dose, μg | ||||||
| ≤50 | 7306 (56.0) | 1599 (57.5) | 0.03 | 1601 (57.6) | 1599 (57.5) | 0 |
| 51-100 | 3897 (29.9) | 814 (29.3) | 0.01 | 787 (28.3) | 814 (29.3) | 0.02 |
| 101-200 | >1800a | 367 (13.2) | 0.03 | 392 (14.1) | 367 (13.2) | 0.03 |
| >200 | NRb | 0 | NA | 0 | 0 | NA |
| Length of levothyroxine duration stable dose before index date, d | ||||||
| Mean (SD) | 270.8 (192.7) | 225.5 (148.1) | 0.26 | 227.7 (146.5) | 225.5 (148.1) | 0.02 |
| Median (IQR) | 213.0 (153.0-309.0) | 185.0 (130.0-272.0) | NA | 190.0 (139.0-269.0) | 185.0 (130.0-272.0) | NA |
| TSH baseline, mIU/L | ||||||
| Mean (SD) | 2.2 (1.1) | 2.2 (1.1) | 0.00 | 2.2 (1.1) | 2.2 (1.1) | 0.02 |
| Median (IQR) [range] | 2.2 (1.3-3.0) [0.3-4.4] | 2.2 (1.3-3.0) [0.3-4.4] | NA | 2.2 (1.4-3.0) [0.3-4.4] | 2.2 (1.3-3.0) [0.3-4.4] | NA |
| Age, y | ||||||
| Mean (SD) | 58.9 (14.5) | 58.6 (14.8) | 0.03 | 58.6 (14.5) | 58.6 (14.8) | 0.01 |
| Median (IQR) | 60.0 (49.0-70.0) | 59.0 (48.0-70.0) | NA | 59.0 (49.0-70.0) | 59.0 (48.0-70.0) | NA |
| Sex | ||||||
| Women | 9605 (73.6) | 2019 (72.6) | 0.02 | 2042 (73.4) | 2019 (72.6) | 0.02 |
| Men | 3444 (26.4) | 761 (27.4) | 0.02 | 738 (26.5) | 761 (27.4) | 0.02 |
| Race and ethnicity | ||||||
| Asian | 563 (4.3) | 142 (5.1) | 0.04 | 142 (5.1) | 142 (5.1) | 0.00 |
| Black | 1364 (10.4) | 253 (9.1) | 0.05 | 249 (9.0) | 253 (9.1) | 0.01 |
| Hispanic | 1508 (11.6) | 293 (10.5) | 0.03 | 273 (9.8) | 293 (10.5) | 0.02 |
| White | 9296 (71.2) | 1999 (71.9) | 0.02 | 2014 (72.4) | 1999 (71.9) | 0.01 |
| Unknown | 318 (2.4) | 93 (3.3) | 0.05 | 102 (3.7) | 93 (3.3) | 0.02 |
| Health plan | ||||||
| Commercial | 8084 (62.0) | 1713 (61.6) | 0.01 | 1745 (62.8) | 1713 (61.6) | 0.02 |
| Medicare Advantage | 4965 (38.0) | 1067 (38.4) | 0.01 | 1035 (37.2) | 1067 (38.4) | 0.02 |
| Census region | ||||||
| Midwest | 1456 (11.2) | 322 (11.6) | 0.01 | 336 (12.1) | 322 (11.6) | 0.02 |
| Northeast | 1345 (10.3) | 353 (12.7) | 0.08 | 360 (12.9) | 353 (12.7) | 0.01 |
| South | 8299 (63.6) | 1701 (61.2) | 0.05 | 1664 (59.8) | 1701 (61.2) | 0.03 |
| West | 1949 (14.9) | 404 (14.5) | 0.01 | 420 (15.1) | 404 (14.5) | 0.02 |
| Prescribing practitioner | ||||||
| Endocrinology | 1029 (7.9) | 282 (10.1) | 0.08 | 291 (10.5) | 282 (10.1) | 0.01 |
| Primary care | 9532 (73.0) | 1925 (69.2) | 0.08 | 1900 (68.3) | 1925 (69.2) | 0.02 |
| Other | 1699 (13.0) | 368 (13.2) | 0.01 | 384 (13.8) | 368 (13.2) | 0.02 |
| Missing/unknown | 789 (6.0) | 205 (7.4) | 0.05 | 205 (7.4) | 205 (7.4) | 0.00 |
| Charlson Comorbidity Index score | ||||||
| Mean (SD) | 1.0 (1.6) | 1.0 (1.6) | 0.02 | 1.0 (1.6) | 1.0 (1.6) | 0.01 |
| Median (IQR) | 0.0 (0.0-1.0) | 0.0 (0.0-1.0) | NA | 0.0 (0.0-1.0) | 0.0 (0.0-1.0) | NA |
| Baseline condition (180 d) | ||||||
| Inflammatory bowel disease | 74 (0.6) | 17 (0.6) | 0.01 | 14 (0.5) | 17 (0.6) | 0.01 |
| Anemia | 622 (4.8) | 150 (5.4) | 0.03 | 147 (5.3) | 150 (5.4) | 0.01 |
| Celiac disease | 19 (0.1) | NRb | 0.02 | 12 (0.4) | NRb | 0.03 |
| Thyroid cancer | 78 (0.6) | 32 (1.2) | 0.06 | 31 (1.1) | 32 (1.2) | 0.00 |
| Thyroid surgery (total) | 71 (0.5) | 16 (0.6) | 0.00 | 17 (0.6) | 16 (0.6) | 0.01 |
| Thyroid surgery lobectomy | 17 (0.1) | NRb | 0.01 | NRb | NRb | 0.01 |
| Baseline estrogen (90 d) | 732 (5.6) | 140 (5.0) | 0.03 | 138 (5.0) | 140 (5.0) | 0.00 |
Abbreviations: NA, not applicable; NR, not reported; SMD, standardized mean difference; TSH, thyrotropin.
a
Exact level is not provided to avoid estimating the numbers of patients receiving more than 200 µg daily of levothyroxine to protect their confidentiality.
b
Cannot report characteristics of fewer than 11 patients to protect patient confidentiality.