Table 1.
Descriptive factors for patients who initiated generic L-thyroxine and continued on the same generic preparation (non-switchers), or switched to another generic L-thyroxine preparation (switchers), including those who subsequently switched once, twice, or more than twice within one year of L-thyroxine initiation
| Non-switcher (N = 385,377) | Switcher |
Total (N = 483,390) | ||||
|---|---|---|---|---|---|---|
| All switchers (N = 98,013) | Switch once (N = 66,161) | Switch twice (N = 23,651) | Switch > 2 (N = 8201) | |||
|
| ||||||
| Age | ||||||
| Mean (SD) | 61.4 (15.2) | 61.7 (15.3) | 62.2 (15.0) | 61.2 (15.6) | 59.0 (16.1) | 61.4 (15.2) |
| Median | 64.0 | 64.0 | 65.0 | 64.0 | 60.0 | 64.0 |
| Q1, Q3 | 51.0, 73.0 | 52.0, 73.0 | 53.0, 73.0 | 51.0, 73.0 | 48.0, 71.0 | 51.0, 73.0 |
| Age group | ||||||
| 18–44 | 59,225 (15.4%) | 14,381 (14.7%) | 9011 (13.6%) | 3789 (16.0%) | 1581 (19.3%) | 73,606 (15.2%) |
| 45–54 | 60,261 (15.6%) | 14,702 (15.0%) | 9693 (14.7%) | 3561 (15.1%) | 1448 (17.7%) | 74,963 (15.5%) |
| 55–64 | 77,145 (20.0%) | 20,454 (20.9%) | 13,718 (20.7%) | 4828 (20.4%) | 1908 (23.3%) | 97,599 (20.2%) |
| 65–74 | 105,499 (27.4%) | 27,078 (27.6%) | 18,948 (28.6%) | 6401 (27.1%) | 1729 (21.1%) | 132,577 (27.4%) |
| 75+ | 83,247 (21.6%) | 21,398 (21.8%) | 14,791 (22.4%) | 5072 (21.4%) | 1535 (18.7%) | 104,645 (21.6%) |
| Gender | ||||||
| Female | 290,254 (75.3%) | 73,256 (74.7%) | 49,518 (74.8%) | 17,725 (74.9%) | 6013 (73.3%) | 363,510 (75.2%) |
| Male | 95,123 (24.7%) | 24,757 (25.3%) | 16,643 (25.2%) | 5926 (25.1%) | 2188 (26.7%) | 119,880 (24.8%) |
| Race | ||||||
| Asian | 12,417 (3.2%) | 3313 (3.4%) | 2265 (3.4%) | 787 (3.3%) | 261 (3.2%) | 15,730 (3.3%) |
| Black | 35,516 (9.2%) | 8696 (8.9%) | 5894 (8.9%) | 2060 (8.7%) | 742 (9.0%) | 44,212 (9.1%) |
| Hispanic | 35,262 (9.2%) | 8363 (8.5%) | 5441 (8.2%) | 2151 (9.1%) | 771 (9.4%) | 43,625 (9.0%) |
| White | 280,604 (72.8%) | 70,301 (71.7%) | 47,939 (72.5%) | 16,588 (70.1%) | 5774 (70.4%) | 350,905 (72.6%) |
| Unknown | 21,578 (5.6%) | 7340 (7.5%) | 4622 (7.0%) | 2065 (8.7%) | 653 (8.0%) | 28,918 (6.0%) |
| L-T4 dose (initial) | ||||||
| ≤50 MCG | 171,081 (44.4%) | 43,341 (44.2%) | 28,772 (43.5%) | 10,468 (44.3%) | 4101 (50.0%) | 214,422 (44.4%) |
| 51–100 MCG | 129,859 (33.7%) | 31,260 (31.9%) | 21,777 (32.9%) | 7281 (30.8%) | 2202 (26.9%) | 161,119 (33.3%) |
| 101–200 MCG | 84,002 (21.8%) | 23,294 (23.8%) | 15,538 (23.5%) | 5876 (24.8%) | 1880 (22.9%) | 107,296 (22.2%) |
| >200 MCG | 435 (0.1%) | 118 (0.1%) | 74 (0.1%) | 26 (0.1%) | 18 (0.2%) | 553 (0.1%) |
| Length of L-T4 before index date | ||||||
| Mean (SD) | 215.1 (97.6) | 204.4 (96.2) | 221.1 (97.1) | 182.4 (82.4) | 133.0 (79.2) | 212.9 (97.4) |
| Median | 224.0 | 207.0 | 231.0 | 188.0 | 128.0 | 219.0 |
| Q1, Q3 | 160.0, 291.0 | 129.0, 281.0 | 156.0, 301.0 | 118.0, 248.0 | 62.0, 192.0 | 155.0, 289.0 |
| No. of T4 fills within 1 year | ||||||
| Mean (SD) | 8.9 (3.8) | 8.9 (3.7) | 8.6 (3.7) | 9.3 (3.7) | 10.7 (3.7) | 8.9 (3.8) |
| Median | 10.0 | 9.0 | 8.0 | 10.0 | 11.0 | 10.0 |
| Q1, Q3 | 5.0, 12.0 | 5.0, 12.0 | 5.0, 12.0 | 6.0, 12.0 | 8.0, 13.0 | 5.0, 12.0 |
| No. of T4 fills within 1 year | ||||||
| 1–5 times | 127,920 (33.2%) | 26,897 (27.4%) | 20,776 (31.4%) | 5545 (23.4%) | 576 (7.0%) | 154,817 (32.0%) |
| 6–10 times | 82,100 (21.3%) | 31,759 (32.4%) | 21,475 (32.5%) | 7276 (30.8%) | 3008 (36.7%) | 113,859 (23.6%) |
| ≥11 times | 175,357 (45.5%) | 39,357 (40.2%) | 23,910 (36.1%) | 10,830 (45.8%) | 4617 (56.3%) | 214,714 (44.4%) |
| No. of pharmacies visited to fill L-T4 | ||||||
| Mean (SD) | 1.3 (0.6) | 1.8 (0.8) | 1.8 (0.8) | 1.7 (0.8) | 1.9 (1.0) | 1.4 (0.7) |
| Median | 1.0 | 2.0 | 2.0 | 1.0 | 2.0 | 1.0 |
| Q1, Q3 | 1.0, 1.0 | 1.0, 2.0 | 1.0, 2.0 | 1.0, 2.0 | 1.0, 2.0 | 1.0, 2.0 |
| Health plan | ||||||
| Commercial | 182,001 (47.2%) | 43,968 (44.9%) | 28,741 (43.4%) | 10817 (45.7%) | 4410 (53.8%) | 225,969 (46.7%) |
| Medicare advantage | 203,376 (52.8%) | 54,045 (55.1%) | 37,420 (56.6%) | 12834 (54.3%) | 3791 (46.2%) | 257,421 (53.3%) |
| Census region | ||||||
| Midwest | 106,697 (27.7%) | 28,188 (28.8%) | 18,818 (28.4%) | 6987 (29.5%) | 2383 (29.1%) | 134,885 (27.9%) |
| Northeast | 53,699 (13.9%) | 13,190 (13.5%) | 9018 (13.6%) | 3074 (13.0%) | 1098 (13.4%) | 66,889 (13.8%) |
| South | 168,652 (43.8%) | 41,976 (42.8%) | 28,595 (43.2%) | 9977 (42.2%) | 3404 (41.5%) | 210,628 (43.6%) |
| West | > 56,320 (>14%)a | >14,650 (>14%)a | >9720 (>14%)a | 3613 (15.3%) | 1316 (16.0%) | >70,980 (>14%)a |
| Other | <11a | <11a | <11a | 0 | 0 | <11a |
| Prescribing provider | ||||||
| Endocrinology | 24,771 (6.4%) | 6018 (6.1%) | 3850 (5.8%) | 1589 (6.7%) | 579 (7.1%) | 30,789 (6.4%) |
| Primary care | 280,750 (72.9%) | 68,189 (69.6%) | 46,664 (70.5%) | 16,200 (68.5%) | 5325 (64.9%) | 348,939 (72.2%) |
| Other | 44,435 (11.5%) | 12,467 (12.7%) | 8048 (12.2%) | 3062 (12.9%) | 1357 (16.5%) | 56,902 (11.8%) |
| Missing/Unknown | 35,421 (9.2%) | 11,339 (11.6%) | 7599 (11.5%) | 2800 (11.8%) | 940 (11.5%) | 46,760 (9.7%) |
| Charlson comorbidity index | ||||||
| Mean (SD) | 1.1 (1.7) | 1.2 (1.9) | 1.2 (1.8) | 1.2 (1.9) | 1.3 (2.1) | 1.1 (1.7) |
| Median | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Q1, Q3 | 0.0, 1.0 | 0.0, 2.0 | 0.0, 2.0 | 0.0, 2.0 | 0.0, 2.0 | 0.0, 2.0 |
| Baseline comorbidities (within 6 months before index date) | ||||||
| Atrial fibrillation | 20,046 (5.2%) | 5765 (5.9%) | 3882 (5.9%) | 1412 (6.0%) | 471 (5.7%) | 25,811 (5.3%) |
| Myocardial infarction | 4551 (1.2%) | 1481 (1.5%) | 976 (1.5%) | 362 (1.5%) | 143 (1.7%) | 6032 (1.2%) |
| Congestive heart failure | 19,160 (5.0%) | 5778 (5.9%) | 3825 (5.8%) | 1447 (6.1%) | 506 (6.2%) | 24,938 (5.2%) |
| Stroke | 6620 (1.7%) | 2147 (2.2%) | 1447 (2.2%) | 512 (2.2%) | 188 (2.3%) | 8767 (1.8%) |
| Thyroid cancer | 4480 (1.2%) | 1622 (1.7%) | 953 (1.4%) | 431 (1.8%) | 238 (2.9%) | 6102 (1.3%) |
| Thyroid surgery (total) | 3149 (0.8%) | 1585 (1.6%) | 798 (1.2%) | 449 (1.9%) | 338 (4.1%) | 4734 (1.0%) |
| Year of index prescription | ||||||
| 2008 | 12,183 (3.2%) | 1952 (2.0%) | 1353 (2.0%) | 430 (1.8%) | 169 (2.1%) | 14,135 (2.9%) |
| 2009 | 23,692 (6.1%) | 3456 (3.5%) | 2582 (3.9%) | 633 (2.7%) | 241 (2.9%) | 27,148 (5.6%) |
| 2010 | 28,538 (7.4%) | 3938 (4.0%) | 2809 (4.2%) | 872 (3.7%) | 257 (3.1%) | 32,476 (6.7%) |
| 2011 | 31,235 (8.1%) | 5069 (5.2%) | 3451 (5.2%) | 1256 (5.3%) | 362 (4.4%) | 36,304 (7.5%) |
| 2012 | 32,710 (8.5%) | 5628 (5.7%) | 3923 (5.9%) | 1321 (5.6%) | 384 (4.7%) | 38,338 (7.9%) |
| 2013 | 31,294 (8.1%) | 7630 (7.8%) | 5381 (8.1%) | 1661 (7.0%) | 588 (7.2%) | 38,924 (8.1%) |
| 2014 | 35,529 (9.2%) | 13,076 (13.3%) | 9436 (14.3%) | 2699 (11.4%) | 941 (11.5%) | 48,605 (10.1%) |
| 2015 | 40,061 (10.4%) | 8381 (8.6%) | 5961 (9.0%) | 1762 (7.5%) | 658 (8.0%) | 48,442 (10.0%) |
| 2016 | 52,235 (13.6%) | 12,913 (13.2%) | 9182 (13.9%) | 2730 (11.5%) | 1001 (12.2%) | 65,148 (13.5%) |
| 2017 | 59,006 (15.3%) | 18,353 (18.7%) | 11,499 (17.4%) | 5075 (21.5%) | 1779 (21.7%) | 77,359 (16.0%) |
| 2018 | 38,894 (10.1%) | 17,617 (18.0%) | 10,584 (16.0%) | 5212 (22.0%) | 1821 (22.2%) | 56,511 (11.7%) |
a
N < 11 cannot be shared to protect patient confidentiality