Drug Concentration, Immunogenicity, and Efficacy Study in Patients With Rheumatoid Arthritis Currently Treated With Etanercept, Adalimumab, or Infliximab

Percentage of participants positive for antidrug antibodies among those treated with etanercept versus those treated with monoclonal antibodies (adalimumab or infliximab) was determined.

Percentage of participants with Low Disease Activity (LDA) (Disease Activity Score based on a 28-joint count [DAS28] Erythrocyte sedimentation rate [ESR] score ≤3.2) among those who are antidrug antibody positive versus negative (all participants receiving etanercept, adalimumab, or infliximab combined).

Serum trough drug concentrations for etanercept, adalimumab, and infliximab compared between participants who are antidrug antibody positive versus negative. Units of measurement for Serum trough drug concentration is µg/mL.

Percentage of participants positive for antidrug antibodies among those treated with etanercept, adalimumab, or infliximab were determined.

The CDAI total scores for etanercept, adalimumab, or infliximab compared between participants who are antidrug antibody positive versus negative. CDAI = Disease activity score (DAS) 28 prorated Swollen Joint Count (0-28) + DAS 28 prorated Tender Joint Count (0-28) + Physician's Global Assessment (0-10) + Subject's Global Assessment (0-10). The total score range is 0-76. Score interpretation: Remission ≤ 2.8; Low Disease Activity CDAI > 2.8 and ≤ 10; Moderate Disease Activity CDAI > 10 and ≤ 22; High Disease Activity CDAI > 22.

The SDAI Total Scores for etanercept, adalimumab, or infliximab compared between participants who are antidrug antibody positive versus negative. SDAI = DAS 28 prorated Swollen Joint Count (0-28) + DAS 28 prorated Tender Joint Count (0-28) + Physician's Global Assessment (0-10) + Subject's Global Assessment (0-10) + C-reactive protein (CRP) (in mg/dL). The total score range is 0-86. Score interpretation: Remission SDAI ≤ 3.3; Low Disease Activity SDAI > 3.3 and ≤ 11; Moderate Disease Activity SDAI > 11 and ≤ 26; High Disease Activity SDAI > 26.

The DAS28 assessment is a derived measurement with differential weight given to each component. DAS28 will be calculated twice, utilizing first ESR, and then CRP as the acute phase reactant: 1) DAS28-ESR = 0.56 sqrt (28 painful/tender joint count) + 0.28 sqrt (28 swollen joint count) + 0.70 (ln ESR) + 0.014 GH, where GH=subject general health VAS (0-100 mm). 2) DAS28-4 CRP = 0.56 sqrt (28 painful/tender joint count) + 0.28 sqrt (28 swollen count) + 0.36 (ln CRP+1) + 0.014 GH + 0.96, where GH=subject general health VAS (0- 100 mm), higher scores were indicative of a worse outcome. The specific components of the DAS28 assessment that were used in this study are: Tender/Painful Joint Count (28), Swollen Joint Count (28), ESR/CRP, and Subject's General Health VAS assessment.

The DAS28 assessment is a derived measurement with differential weight given to each component. DAS28 will be calculated twice, utilizing first ESR, and then CRP as the acute phase reactant: 1) DAS28-ESR = 0.56 sqrt (28 painful/tender joint count) + 0.28 sqrt (28 swollen joint count) + 0.70 (ln ESR) + 0.014 GH, where GH=subject general health VAS (0 100 mm). 2) DAS28-4 CRP = 0.56 sqrt (28 painful/tender joint count) + 0.28 sqrt (28 swollen count) + 0.36 (ln CRP+1) + 0.014 GH + 0.96, where GH=subject general health VAS (0-100 mm), higher scores were indicative of a worse outcome. The specific components of the DAS28 assessment that were used in this study are: Tender/Painful Joint Count (28), Swollen Joint Count (28), ESR/CRP, and Subject's General Health VAS assessment.

The HAQ-DI assesses the degree of difficulty a participant has experienced during the past week in 8 domains of daily living activities: dressing and grooming, arising, eating, walking, hygiene, reach, grip, and other activities. Each activity category consists of 2-3 items. For each question in the questionnaire, the level of difficulty is scored from 0 to 3 with 0 representing "no difficulty," 1 as "some difficulty," 2 as "much difficulty," and 3 as "unable to do." Any activity that requires assistance from another individual or requires the use of an assistive device adjusts to a minimum score of 2 to represent a more limited functional status. The total score range for the HAQ-DI scale, minimum score was 0 (best), maximum score was 3 (worst).

HAQ DI (<=0.5) scores for etanercept, adalimumab, or infliximab compared between participants who are antidrug antibody positive versus negative.

Correlation of antidrug antibody titers with efficacy measures analysed using Spearman correlation coefficient.

Correlation of antidrug antibody titers with trough drug concentration analysed using Spearman correlation coefficient.