The -174G/C Interleukin-6 Gene Promoter Polymorphism as a Genetic Marker of Differences in Therapeutic Response to Methotrexate and Leflunomide in Rheumatoid Arthritis
Table 3
Evaluation of -174G/C IL-6 as predictor of therapeutic response to any treatment (MTX or LEF) defining nonresponse, as DAS-28 > 3.2 at 3 or 6 months in rheumatoid arthritis (RA).
Treatment with any treatment MTX or LEF,
Follow-up at 3 months
MTX and LEF nonresponse
MTX and LEF response
RR
95% CI
Genotype
GG (%)
47 (87.0)
7 (13.0)
—
—
0.62
GC (%)
25 (80.6)
6 (19.4)
—
—
CC (%)
10 (91)
1 (9)
—
—
GG versus GC (as referent)
—
—
1.08
0.88 to 1.32
0.20
GG versus CC (as referent)
—
—
0.96
0.77 to 1.18
0.39
GC versus CC (as referent)
—
—
0.88
0.73 to 1.14
0.40
Genetic models
Dominant model (GG versus GC + CC as referent)
—
—
1.04
0.88 to 1.24
0.41
Recessive model (GG + GC versus CC as referent)
—
—
0.93
0.76 to 1.16
0.49
Alleles 2n = 192
2n = 164
2n = 28
G allele, (%)
119 (85.6)
20 (14.4)
1.00
0.88 to 1.15
0.44
C allele, (%)
45 (84.9)
8 (15.1)
Referent
—
Follow-up at 6 months
MTX and LEF nonresponse
MTX and LEF response
RR
95% Cl
Genotype
GG (%)
50 (92.6)
4 (7.4)
—
—
0.13
GC (%)
24 (77.4)
7 (22.6)
—
—
CC (%)
10 (90.9)
1 (9.1)
—
—
GG versus GC (as referent)
—
—
1.19
1.07 to 1.56
0.03
GG versus CC (as referent)
—
—
1.01
0.81 to 1.24
0.61
GC versus CC (as referent)
—
—
0.85
0.65 to 1.11
0.31
Genetic models
Dominant model (GG versus GC + CC as referent)
—
—
1.19
0.96 to 1.35
0.05
Recessive model (GG + GC versus CC as referent)
—
—
0.93
0.78 to 1.17
0.58
Alleles 2n = 192
2n = 168
2n = 24
G allele, (%)
124 (89.2)
15 (10.8)
1.07
0.94 to 1.23
0.13
C allele, (%)
44 (83.0)
9 (17.0)
Referent
—
MTX: methotrexate; LEF: leflunomide; DAS-28: Disease Activity Score for 28 joints; GG: excisable homozygote genotype; GC: heterozygote genotype; CC: homozygote genotype. Qualitative variables were expressed in frequency (%); RR: Relative Risk; 95% CI: 95% Confidence Interval. Therapeutic failure (nonresponse) was defined if patients did not achieve remission or low disease activity (DAS-28 < 3.2).
