Anti-drug antibodies in Colombian patients with rheumatoid arthritis treated with Enbrel vs Etanar – Preliminary report

Figures & data

Table 1. Clinical, laboratory and treatment characteristics.

Variable	% (n/N)
Gender (woman)	87.5 (28/32)
FAI	15.6 (5/32)
CVD	31.5 (10/32)
Dyslipidemia	12.5 (4/32)
DM2	6.5 (2/32)
Osteoporosis	12.5 (4/32)
Hypothyroidism	21.9 (7/32)
EAM	6.25 (2/32)
Erosiveness	68 (17/25)
RF (+)	83.9 (26/31)
Anti-CCP (+)	90.9 (20/22)
ANA (+)	68.8 (11/16)
ENA (+)	25 (3/12)
RF (+) and anti-CCP (+)	90 (18/20)
RF (–) and anti-CCP (–)	5 (1/20)
Positive CRP	18.8 (6/32)
ESR >20 mm/h	21.9 (7/32)
Prednisolone	50.0 (16/32)
Deflazacort	9.4 (3/32)
DMARDc	81.2 (26/32)
Methotrexate	56.2 (18/32)
Prednisolone	50.0 (16/32)
Leflunomide	9.4 (3/32)
Chloroquine	15.6 (5/32)
DMARDb	25.0 (8/32)

FAI: family autoimmunity; CVD: cardiovascular disease; DM2: diabetes mellitus type 2; EAM: extra-articular manifestations; RF: rheumatoid factor; anti-CCP: anti-cyclic-citrullinated peptide antibodies; ANA: anti-nuclear antibodies; ENA: extractable nucleus antibodies; CRP: C-reactive protein; ESR: erythrocyte sedimentation rate. DMARD: disease-modifying anti-rheumatic drugs; DMARDc: conventional DMARD; DMARDb: biological DMARD.

Figure 1. Reactogenicity in ELISA (i.e. ADAb-positive outcomes) among samples from patients in the Enbrel^® (N = 16) and in the Etanar^® (N = 16) groups.

Figure 2. Distribution of DAS28-PCR (disease activity score by C-reactive protein) values based on positive or negative reactogenicity in ELISA. Dark line shows mean for each group of values and box shows values between first and third quartiles. Upper and lower value limits for each group are likewise shown. pos: positive. neg: negative.

Figure 3. Effect plot of DAS28-CRP on ELISA seropositivity. Gray area correspond to 95% prediction interval. DAS28-CRP was a variable preserved from the logistic regression analysis build to explain the variation in seropositivity of the ELISA test with respect to other variables, after applying the stepwise algorithm based on the Akaike information criterion (Venables & Ripley 2002).

Table 2. ELISA absorbance and DAS-28 scores for all patients organized by time of treatment with Enbrel^® or Etanar^®.

Drug	Months of treatment	ELISA	DAS28-ESR	DAS28-CRP
Enbrel	1	0.104	3.65	2.92
Etanar	4	0.044	2.23	3.05
Etanar	4	0.058	4.51	5.33
Etanar	5	0.043	3.23	2.11
Enbrel	6	0.042	2.33	2.32
Etanar	7	0.042	4.52	3.37
Etanar	8	0.039	1.32	1.56
Enbrel	8	0.040	3.43	2.48
Etanar	12	0.046	3.21	4.18
Etanar	12	0.051	3.25	2.27
Etanar	18	0.043	3.25	3.97
Enbrel	18	0.046	2.11	1.10
Etanar	18	0.048	2.88	1.65
Enbrel	23	0.064	2.09	1.55
Etanar	24	0.043	0.56	1.43
Enbrel	24	0.074	3.17	3.16
Etanar	32	0.046	2.84	1.71
Enbrel	36	0.041	1.09	1.57
Etanar	36	0.042	0.70	1.17
Etanar	36	0.049	1.13	1.54
Etanar	36	0.050	2.48	1.66
Enbrel	36	0.054	1.03	1.02
Enbrel	36	0.057	1.89	1.64
Enbrel	48	0.046	4.01	3.57
Enbrel	48	0.048	1.61	1.03
Enbrel	48	0.965	2.76	2.60
Etanar	59	0.042	1.74	1.24
Etanar	72	0.042	4.01	3.44
Enbrel	72	0.051	3.45	2.92
Enbrel	84	0.047	1.07	1.64
Enbrel	100	0.044	2.72	2.11
Enbrel	144	0.052	0.70	1.67
Average	34.8	0.051	2.47	2.28

Cases that were positive based on ELISA are in bold (ELISA cutoff ≥0.056).

Table 3. Average of DAS28 scores for each sub-group of patients according to drug.

DAS-28	Total	Enbrel^®	Etanar^®	p value
DAS28-ESR	2.47	2.32	2.62	0.472
DAS28-CRP	2.28	2.08	2.48	0.291

DAS28-ESR: disease activity score calculated with erythrocyte sedimentation rate value; DAS28-CRP: disease activity score calculated with C-reactive protein value.

Table 4. Average of DAS28 scores for patients negative or positive in the ELISA test.

DAS-28	Total	Negative	Positive	p value
DAS28-ESR	2.47	2.34	3.01	0.201
DAS28-CRP	2.28	2.15	2.87	0.132

DAS: disease activity score; ESR: erythrocyte sedimentation rate; CRP: C-reactive protein; ELISA: enzyme-linked immunosorbent assay.

Venables W, Ripley B, editors. 2002. Modern applied statistics with issues of accuracy and scale. New York: Springer.

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