Table 2.
Correlations between serum iron, ferritin, and hepcidin levels and other parameters.
| Correlation coefficients | Adjusted correlation coefficients* | |||||
|---|---|---|---|---|---|---|
| Fe | Ferritin | Log(hep + 1) | Fe | Ferritin | Log(hep + 1) | |
| Serum iron | 1.000 | 0.318 | 0.307 | 1.000 | 0.251 | 0.401 |
| (<0.001) | (<0.001) | (<0.001) | (<0.001) | |||
| Serum ferritin | 0.318 | 1.000 | 0.816 | 0.251 | 1.000 | 0.657 |
| (<0.001) | (<0.001) | (<0.001) | (<0.001) | |||
| Log(hep + 1) | 0.307 | 0.816 | 1.000 | 0.401 | 0.657 | 1.000 |
| (<0.001) | (<0.001) | (<0.001) | (<0.001) | |||
| Age | −0.161 | 0.092 | 0.072 | — | — | — |
| (0.009) | (0.137) | (0.249) | ||||
| Body mass index | −0.021 | −0.011 | −0.024 | — | — | — |
| (0.732) | (0.856) | (0.697) | ||||
| Disease duration | −0.050 | −0.042 | −0.023 | 0.044 | 0.047 | 0.057 |
| (0.416) | (0.494) | (0.707) | (0.489) | (0.460) | (0.370) | |
| eGFR | 0.055 | 0.002 | 0.004 | — | — | — |
| (0.378) | (0.980) | (0.946) | ||||
| Red blood cell | 0.024 | −0.121 | −0.123 | −0.006 | −0.139 | −0.101 |
| (0.694) | (0.050) | (0.047) | (0.922) | (0.028) | (0.110) | |
| Hemoglobin | 0.400 | 0.196 | 0.125 | 0.420 | 0.127 | 0.243 |
| (<0.001) | (0.001) | (0.043) | (<0.001) | (0.045) | (<0.001) | |
| Hematocrit | 0.305 | 0.120 | 0.054 | 0.318 | 0.060 | 0.138 |
| (<0.001) | (0.052) | (0.383) | (<0.001) | (0.347) | (0.029) | |
| Platelet | −0.241 | −0.173 | −0.172 | −0.186 | −0.064 | −0.203 |
| (<0.001) | (0.005) | (0.005) | (0.003) | (0.315) | (0.001) | |
| UIBC | −0.517 | −0.707 | −0.708 | −0.646 | −0.499 | −0.669 |
| (<0.001) | (<0.001) | (<0.001) | (<0.001) | (<0.001) | (<0.001) | |
| DAS28-ESR | −0.316 | 0.109 | 0.100 | −0.236 | 0.184 | 0.030 |
| (<0.001) | (0.079) | (0.108) | (<0.001) | (0.003) | (0.633) | |
| DAS28-CRP | −0.223 | 0.151 | 0.133 | −0.100 | 0.140 | 0.091 |
| (<0.001) | (0.014) | (0.032) | (0.114) | (0.026) | (0.152) | |
| SDAI | −0.175 | 0.107 | 0.093 | −0.100 | 0.176 | 0.034 |
| (0.004) | (0.083) | (0.132) | (0.114) | (0.005) | (0.588) | |
| CDAI | −0.148 | 0.094 | 0.068 | −0.095 | 0.172 | 0.034 |
| (0.016) | (0.131) | (0.273) | (0.133) | (0.06) | (0.596) | |
| HAQ-DI | −0.167 | −0.068 | −0.047 | −0.138 | 0.005 | −0.117 |
| (0.007) | (0.281) | (0.451) | (0.031) | (0.933) | (0.068) | |
| Rheumatoid factor | 0.014 | 0.061 | 0.029 | 0.003 | 0.028 | 0.005 |
| (0.823) | (0.324) | (0.636) | (0.960) | (0.665) | (0.940) | |
| ESR | −0.344 | 0.112 | 0.143 | −0.178 | 0.178 | 0.075 |
| (<0.001) | (0.070) | (0.021) | (0.005) | (0.005) | (0.241) | |
| CRP | −0.235 | 0.219 | 0.257 | — | — | — |
| (<0.001) | (<0.001) | (<0.001) | ||||
| MMP-3 | −0.206 | 0.051 | −0.005 | −0.053 | 0.187 | −0.010 |
| (0.001) | (0.412) | (0.930) | (0.402) | (0.003) | (0.874) | |
| Daily PSL dose | −0.197 | −0.049 | −0.163 | −0.320 | 0.052 | −0.115 |
| (0.001) | (0.433) | (0.008) | (0.617) | (0.413) | (0.058) | |
| Weekly MTX dose | 0.004 | 0.028 | −0.056 | −0.043 | 0.120 | −0.0r06 |
| (0.954) | (0.655) | (0.371) | (0.505) | (0.058) | (0.930) | |
| Serum bone Alkaline phosphatase | −0.055 | −0.003 | −0.001 | 0.098 | −0.024 | −0.034 |
| (0.376) | (0.957) | (0.986) | (0.122) | (0.710) | (0.588) | |
| Serum TRACP-5b | −0.130 | −0.008 | −0.018 | −0.0749 | −0.074 | −0.053 |
| (0.035) | (0.894) | (0.777) | (0.227) | (0.244) | (0.405) | |
| Serum adjusted calcium | 0.013 | 0.086 | 0.071 | −0.007 | 0.094 | 0.056 |
| (0.830) | (0.165) | (0.249) | (0.910) | (0.139) | (0.378) | |
| Serum phosphate | 0.000 | −0.021 | 0.063 | −0.043 | 0.011 | 0.083 |
| (0.998) | (0.730) | (0.310) | (0.497) | (0.861) | (0.193) | |
| Serum 25(OH)D | 0.046 | 0.250 | 0.193 | 0.042 | 0.200 | 0.202 |
| (0.461) | (<0.001) | (0.002) | (0.510) | (0.001) | (0.001) | |
| Serum FGF 23 | 0.009 | 0.040 | −0.019 | 0.089 | 0.108 | 0.029 |
| (0.889) | (0.523) | (0.763) | (0.160) | (0.089) | (0.644) | |
| Femoral T score | 0.230 | 0.006 | −0.038 | 0.127 | 0.022 | 0.002 |
| (<0.001) | (0.919) | (0.543) | (0.045) | (0.726) | (0.973) | |
| Femoral Z score | 0.150 | 0.067 | 0.044 | 0.126 | 0.041 | 0.044 |
| (0.015) | (0.279) | (0.479) | (0.048) | (0.516) | (0.487) | |
| Lumbar T score | 0.067 | −0.044 | −0.110 | −0.047 | 0.028 | −0.072 |
| (0.283) | (0.480) | (0.076) | (0.459) | (0.658) | (0.3257) | |
| Lumbar Z score | 0.004 | −0.002 | −0.051 | −0.055 | 0.039 | −0.043 |
| (0.953) | (0.973) | (0.410) | (0.389) | (0.188) | (0.501) | |
| Annual change of femoral T score | 0.071 | −0.104 | −0.031 | 0.001 | −0.132 | −0.021 |
| 0.284 | 0.115 | 0.640 | (0.989) | (0.050) | (0.762) | |
| Annual change of lumbar T score | 0.046 | 0.135 | 0.146 | 0.011 | 0.086 | 0.151 |
| 0.486 | 0.041 | 0.026 | (0.869) | (0.206) | (0.026) | |
*Adjusted for age, sex, BMI, eGFR, CRP, PSL use, bDMARD use, anti-resorption drug use, teriparatide use, and iron agent use.
eGFR, estimated glomerular filtration rate; UIBC, unsaturated iron binding capacity; DAS28, disease activity scores in 28 joints; ESR, erythrocyte sedimentation rate; CRP, C-reactive protein; SDAI, simplified disease activity index; CDAI, clinical disease activity index; HAQ-DI, health assessment questionnaire without disability index; MMP-3, matrix metalloprotease 3; PSL, prednisolone; MTX, methotrexate; TRACP-5b, tartrate-resistant acid phosphatase-5b; 25(OH)D, 25-hydroxy vitamin D; FGF23, fibroblast growth factor 23.
Annual change of T score was evaluated in 231 patients and the mean observational period was 2.0 ± 0.33 years (0.63–3.25).