Table 3.
Probit Models of Biologic Initiation and Continuation
| Use Biologic Conditional on Not Having Used It before |
Use Biologic Conditional on Initiation |
|||||
|---|---|---|---|---|---|---|
| All Newly Diagnosed | Newly Diagnosed with Other Family | Newly Diagnosed with Other Family | All Biologic Initiators | Biologic Initiators with Other Family | Biologic Initiators with Other Family | |
| (1) | (2) | (3) | (4) | (5) | (6) | |
| Probit | Probit | IV Probit | Probit | Probit | IV Probit | |
| Average plan biologic OOP costs under medical benefits (in U.S.$100) | 0.0017 | 0.0017 | 0.0010 | −3.5e-05 | −4e-04 | −2.5e-04 |
| (0.0012) | (0.0014) | (0.0010) | (0.001) | (0.002) | (0.002) | |
| Average plan biologic OOP costs under pharmacy benefits (in U.S.$100) | −0.012*** | 0.010** | −0.011** | −0.01* | −0.02*** | −0.02*** |
| (0.004) | (0.005) | (0.005) | (0.006) | (0.006) | (0.006) | |
| Other family OOP in top quartile within the plan | 0.047 | −0.494*** | −0.070 | 0.045 | ||
| (0.047) | (0.178) | (0.067) | (0.299) | |||
| Used an analgesic or NSAID previous year | 0.070* | 0.051 | 0.075 | 0.056 | 0.100 | 0.099 |
| (0.041) | (0.047) | (0.046) | (0.058) | (0.069) | (0.069) | |
| Used a corticosteroid previous year | 0.217*** | 0.221*** | 0.212*** | −0.099* | −0.091 | −0.095 |
| (0.041) | (0.047) | (0.046) | (0.055) | (0.066) | (0.067) | |
| Used a nonbiologic DMARD previous year | 0.622*** | 0.618*** | 0.607*** | 0.018 | 0.024 | 0.024 |
| (0.044) | (0.052) | (0.052) | (0.058) | (0.069) | (0.069) | |
| No. of years from first RA diagnosis | −0.157*** | −0.159*** | −0.144*** | |||
| (0.020) | (0.024) | (0.023) | ||||
| No. of years from first biologic | −0.131*** | −0.117*** | −0.116*** | |||
| (0.022) | (0.027) | (0.027) | ||||
| Age 25–44 | 0.145 | 0.130 | −0.057 | 0.260 | 0.352 | 0.404 |
| (0.167) | (0.214) | (0.216) | (0.265) | (0.353) | (0.374) | |
| Age 45–64 | 0.177 | 0.186 | −0.021 | 0.446* | 0.579 | 0.633* |
| (0.159) | (0.209) | (0.215) | (0.259) | (0.354) | (0.376) | |
| Age 65+ | −0.063 | −0.027 | −0.174 | 0.257 | 0.467 | 0.511 |
| (0.165) | (0.217) | (0.215) | (0.266) | (0.364) | (0.377) | |
| Currently working | 0.024 | 0.030 | −0.009 | 0.109 | 0.195** | 0.205** |
| (0.055) | (0.063) | (0.062) | (0.086) | (0.098) | (0.101) | |
| Median HH income (in U.S.$1,000) | 1.786 | 1.482 | 2.050 | 2.030 | 1.885 | 2.016 |
| (1.840) | (2.066) | (2.025) | (3.163) | (3.578) | (3.583) | |
| Married | 0.058 | 0.021 | 0.114 | 0.056 | −0.089 | −0.112 |
| (0.056) | (0.152) | (0.149) | (0.083) | (0.249) | (0.256) | |
| Male | 0.048 | −0.026 | −0.008 | 0.100 | 0.090 | 0.081 |
| (0.047) | (0.056) | (0.055) | (0.080) | (0.091) | (0.093) | |
| Urban | 0.107 | 0.359 | 0.369 | −0.178 | −0.231 | −0.231 |
| (0.214) | (0.284) | (0.277) | (0.430) | (0.420) | (0.423) | |
| Primary beneficiary | −0.043 | −0.001 | −0.030 | 0.032 | 0.002 | 0.011 |
| (0.051) | (0.052) | (0.052) | (0.080) | (0.083) | (0.084) | |
| Asthma | −0.066 | −0.064 | −0.033 | −0.270* | −0.278 | −0.278 |
| (0.096) | (0.112) | (0.110) | (0.142) | (0.172) | (0.171) | |
| Hypertension | −0.126*** | −0.077 | −0.060 | −0.100 | −0.134 | −0.134 |
| (0.047) | (0.056) | (0.055) | (0.073) | (0.088) | (0.088) | |
| Diabetes | −0.099 | −0.118 | −0.113 | −0.132 | −0.135 | −0.136 |
| (0.071) | (0.087) | (0.085) | (0.107) | (0.130) | (0.130) | |
| Hyperlipidemia | −0.155** | −0.208** | −0.194** | 0.003 | 0.097 | 0.098 |
| (0.069) | (0.085) | (0.083) | (0.112) | (0.138) | (0.139) | |
| Heart disease | −0.090 | −0.032 | −0.020 | −0.168** | −0.072 | −0.079 |
| (0.061) | (0.074) | (0.071) | (0.085) | (0.106) | (0.107) | |
| Depression | −0.026 | −0.061 | −0.049 | 0.068 | −0.070 | −0.075 |
| (0.081) | (0.100) | (0.098) | (0.135) | (0.170) | (0.170) | |
| Osteoarthritis | −0.113** | −0.051 | −0.029 | −0.263*** | −0.214** | −0.214** |
| (0.053) | (0.063) | (0.061) | (0.084) | (0.104) | (0.104) | |
| Year fixed effects | Included | Included | Included | Included | Included | Included |
| Observations | 18,697 | 12,183 | 12,183 | 4,608 | 3,207 | 3,207 |
Notes. Standard errors (clustered at the individual level) in parentheses.
*
Significant at 10%;
**
Significant at 5%;
***
Significant at 1%.
BRM, biologic response modifiers; DMARDS, disease-modifying antirheumatic drugs; HH, household; IV, instrumental variables; NSAID, nonsteroidal antiinflammatory drugs; RA, rheumatoid arthritis.