Monitoring Drug and Antidrug Levels: A Rational Approach in Rheumatoid Arthritis Patients Treated with Biologic Agents Who Experience Inadequate Response While Being on a Stable Biologic Treatment

Table 1

Patient's characteristics at the moment of dosing biologic drug level.

Biologic agent	Current biologic treatment, duration, and mean	DAS28 baseline, mean	SDAI baseline, mean	csDMARD associated, no (%)	ACPA positive, no (%)	RF positive, no (%)
RTX
Group A	48.8±53.4	3.65±1.12	20.0±15.7	15 (60%)	14 (56%)	16 (64%)
Group B	27.7±13.7	3.45±1.19	21.7±29.6	8 (32%)	4 (16%)	7 (28%)
𝑃	0.294	0.678	0.845	0.667	0.021	0.049
IFX
Group A	40.6±39.9	3.57±1.25	15.2±19.7	6 (30%)	4 (20%)	7 (35%)
Group B	29.3±17.5	5.42±1.19	43.2±29.6	6 (30%)	3 (15%)	4 (20%)
𝑃	0.379	0.003	0.026	0.582	0.515	0.064
ETN
Group A	47.8±38.5	4.14±1.44	31.6±31.3	10 (55.55%)	11 (61.11%)	12 (66.67%)
Group B	57.6±23.7	5.25±1.79	41.5±40.3	3 (16.67%)	2 (11.11%)	2 (11.11%)
𝑃	0.679	0.259	0.639	0.239	0.814	0.612
ADL
Group A	46.7±25.2	3.39±1.04	10.1±6.05	7 (77.78%)	4 (44.44%)	6 (66.67%)
Group B	36	3.54	32.9	1 (11.11%)	1 (11.11%)	1 (11.11%)
𝑃	0.700	0.902	0.009	0.708	0.495	0.571

Differences between patient's baseline characteristics were tested by Student’s 𝑡-test or chi-square test.
RTX: rituximab; IFX: infliximab; ETN: etanercept; ADL: adalimumab.
Group A: detectable drug level; Group B: undetectable drug level.
csDMARD: conventional synthetic disease modifying antirheumatic drug; ACPA: anticitrullinated peptides antibodies status; RF: rheumatoid factor status.