therapy. Data were collected using the IBM Watson Health MarketScan® Commercial Claims and Encounters (contains healthcare experiences of privately insured individuals), Medicare Supplemental and Coordination of Benefits (contains same information as commercial claims and encounters for individuals with Medicare Supplemental insurance paid by employers), and Early View Databases (captures same components of Commercial and Medicare Databases for services incurred as late as approximately 45 days before data release). The datasets comply with Health Insurance Portability and Accountability Act (HIPAA), 1996. This study did not involve the collection, use, or transmittal of individually identifiable data; therefore, Institutional Review Board (IRB) approval was not required.
Selection Criteria and Study Time Period
Adult patients were included if they had at least one inpatient claim or two non-diagnostic outpatient claims (at least 30 days apart) with psoriasis diagnosis between March 1, 2015 and October 31, 2019. International Classification of Diseases (ICD), 9th and 10th Revision, Clinical Modification (ICD-9-CM diagnosis code 696.1x or ICD-10-CM diagnosis codes L40.0–L40.4 or L40.8-L40.9) were used to identify records of patients with psoriasis. Patients were required to have ≥1 claim for the index drug of interest IXE or ADA between March 1, 2016 and October 31, 2019 with a psoriasis diagnosis on or before the date of the first claim of interest. The date of the first index drug claim set the index date and assigned patients to the IXE or ADA cohort. Patients were required to be ≥18 years of age at index date and continuously enrolled with medical and pharmacy benefits for at least 6 months before (pre-period) and 24 months after (postperiod) the index date. Patients with index drug indications other than psoriasis (such as psoriatic arthritis for both IXE and ADA and ankylosing spondylitis, juvenile idiopathic arthritis, rheumatoid arthritis, Crohn’s disease, ulcerative colitis, hidradenitis suppurativa, and uveitis for ADA) in the 6-month pre-period were excluded. Patients with index medications (ADA / IXE) within 90 days before the index date were also excluded. Patients were followed for 24 months starting from the index date. '
Study Outcomes Definitions
Treatment adherence, persistence, discontinuation, reinitiation, dosing, and switching were assessed during a 24-month followup period. Adherence was measured by proportion of days covered (PDC) defined as the number of days with medication on hand during the follow-up period divided by the total number of days in the follow-up period. Mean PDC was reported, and high adherence was defined as PDC ≥80%. Patients were considered on persistent treatment if they had a <60-day gap between the end-of-day supply of the prior script to the next refill. The proportion of patients who stayed on persistent treatment during a 24-month follow-up period and time to non-persistence were captured and reported. Discontinuation was defined as having a gap of 90 days without any refill of the index drug after the days’ supply of the previous script was exhausted. The proportion of patients who reached discontinuation during a 24-month followup period and time to discontinuation were reported. Among those who discontinued the index therapy, reinitiation was captured when the patients had ≤1 claim of index drug after the discontinuation date. The proportion of patients who reinitiated and time from discontinuation to reinitiation were reported. Switching was defined by starting a new biologic for psoriasis after discontinuing the index biologic. The proportion of patients who switched and time to switching were captured.
The average daily dose was reported for patients who had no index drug in the pre-period and had both the induction and maintenance period. Daily dosage was calculated as quantity multiplied by strength divided by days of supply. Quantity, strength, and days of supply were available in pharmacy claims billed by the National Drug Codes. When ADA was administered in doctor’s office and billed by Healthcare Common Procedure Coding System codes, quantity was estimated based on the unit field recorded on the claim. If it was either missing or outside of the expected range (≤0 or >4), the paid amount on the claim divided by the wholesale acquisition cost was used as a proxy for quantity. A 14-day supply was assigned for each injection based on the recommended injection schedule for ADA.18 The maintenance period started with the first claim after the induction period. The average daily dose for the induction and maintenance period for IXE and ADA were reported and compared to the expected daily dose based on dosing information in drug package inserts.18,19
Covariates
Baseline demographic and clinical variables (including age, gender, primary payer, health plan type, geographic region) were measured at the index date. Clinical variables Deyo Charlson Comorbidity Index (DCCI), Comorbid conditions (anxiety, coronary heart disease, depression, diabetes, hyperlipidemia, hypertension, obesity, other autoimmune disorders, osteoarthritis, peripheral vascular disease, and sleep apnea) were also included and measured at 6-months pre-index period. Pre-period use of biologics (ADA, brodalumab, certolizumab pegol, etanercept, guselkumab, infliximab, IXE, secukinumab, and ustekinumab), systemic drugs (apremilast, acitretin, systemic corticosteroids, cyclosporine, and methotrexate), topical drugs (coal tar, ketoconazole topical, and topical steroids), and non-pharmacologic treatments (phototherapy or laser treatments) were collected during the pre-index period. In addition, pre-period all-cause and psoriasis-related healthcare costs and comorbidity-related costs were collected.
Statistical Analysis
Categorical variables were presented as the count and proportion of patients in each category. Continuous variables were summarized by mean and standard deviation (SD).
Selection Criteria and Study Time Period
Adult patients were included if they had at least one inpatient claim or two non-diagnostic outpatient claims (at least 30 days apart) with psoriasis diagnosis between March 1, 2015 and October 31, 2019. International Classification of Diseases (ICD), 9th and 10th Revision, Clinical Modification (ICD-9-CM diagnosis code 696.1x or ICD-10-CM diagnosis codes L40.0–L40.4 or L40.8-L40.9) were used to identify records of patients with psoriasis. Patients were required to have ≥1 claim for the index drug of interest IXE or ADA between March 1, 2016 and October 31, 2019 with a psoriasis diagnosis on or before the date of the first claim of interest. The date of the first index drug claim set the index date and assigned patients to the IXE or ADA cohort. Patients were required to be ≥18 years of age at index date and continuously enrolled with medical and pharmacy benefits for at least 6 months before (pre-period) and 24 months after (postperiod) the index date. Patients with index drug indications other than psoriasis (such as psoriatic arthritis for both IXE and ADA and ankylosing spondylitis, juvenile idiopathic arthritis, rheumatoid arthritis, Crohn’s disease, ulcerative colitis, hidradenitis suppurativa, and uveitis for ADA) in the 6-month pre-period were excluded. Patients with index medications (ADA / IXE) within 90 days before the index date were also excluded. Patients were followed for 24 months starting from the index date. '
Study Outcomes Definitions
Treatment adherence, persistence, discontinuation, reinitiation, dosing, and switching were assessed during a 24-month followup period. Adherence was measured by proportion of days covered (PDC) defined as the number of days with medication on hand during the follow-up period divided by the total number of days in the follow-up period. Mean PDC was reported, and high adherence was defined as PDC ≥80%. Patients were considered on persistent treatment if they had a <60-day gap between the end-of-day supply of the prior script to the next refill. The proportion of patients who stayed on persistent treatment during a 24-month follow-up period and time to non-persistence were captured and reported. Discontinuation was defined as having a gap of 90 days without any refill of the index drug after the days’ supply of the previous script was exhausted. The proportion of patients who reached discontinuation during a 24-month followup period and time to discontinuation were reported. Among those who discontinued the index therapy, reinitiation was captured when the patients had ≤1 claim of index drug after the discontinuation date. The proportion of patients who reinitiated and time from discontinuation to reinitiation were reported. Switching was defined by starting a new biologic for psoriasis after discontinuing the index biologic. The proportion of patients who switched and time to switching were captured.
The average daily dose was reported for patients who had no index drug in the pre-period and had both the induction and maintenance period. Daily dosage was calculated as quantity multiplied by strength divided by days of supply. Quantity, strength, and days of supply were available in pharmacy claims billed by the National Drug Codes. When ADA was administered in doctor’s office and billed by Healthcare Common Procedure Coding System codes, quantity was estimated based on the unit field recorded on the claim. If it was either missing or outside of the expected range (≤0 or >4), the paid amount on the claim divided by the wholesale acquisition cost was used as a proxy for quantity. A 14-day supply was assigned for each injection based on the recommended injection schedule for ADA.18 The maintenance period started with the first claim after the induction period. The average daily dose for the induction and maintenance period for IXE and ADA were reported and compared to the expected daily dose based on dosing information in drug package inserts.18,19
Covariates
Baseline demographic and clinical variables (including age, gender, primary payer, health plan type, geographic region) were measured at the index date. Clinical variables Deyo Charlson Comorbidity Index (DCCI), Comorbid conditions (anxiety, coronary heart disease, depression, diabetes, hyperlipidemia, hypertension, obesity, other autoimmune disorders, osteoarthritis, peripheral vascular disease, and sleep apnea) were also included and measured at 6-months pre-index period. Pre-period use of biologics (ADA, brodalumab, certolizumab pegol, etanercept, guselkumab, infliximab, IXE, secukinumab, and ustekinumab), systemic drugs (apremilast, acitretin, systemic corticosteroids, cyclosporine, and methotrexate), topical drugs (coal tar, ketoconazole topical, and topical steroids), and non-pharmacologic treatments (phototherapy or laser treatments) were collected during the pre-index period. In addition, pre-period all-cause and psoriasis-related healthcare costs and comorbidity-related costs were collected.
Statistical Analysis
Categorical variables were presented as the count and proportion of patients in each category. Continuous variables were summarized by mean and standard deviation (SD).
