Table 2.
Baseline determinants of the pharmacokinetics of rituximab
| miRAMM W2 | miRAMM AUC | ELISA W2 | ELISA AUC | |||||
|---|---|---|---|---|---|---|---|---|
| Baseline determinants | Median (IQR) | P-valuea | Median (IQR) | P-value | Median (IQR) | P-value | Median (IQR) | P-value |
| Sex | ||||||||
| Male | 113 (92–144) | 0.001 | 6707 (5702–9738) | 0.008 | 103 (88–118) | <0.001 | 5792 (4613–7052) | <0.001 |
| Female | 145 (128–174) | 8918 (7132–11315) | 129 (114–145) | 7545 (6415–9254) | ||||
| ANCA | ||||||||
| PR3 | 138 (102–172) | 0.48 | 8511 (5984–10210) | 0.62 | 114 (96–135) | 0.68 | 6735 (5350–8472) | 0.59 |
| MPO | 133 (96–151) | 8322 (5680–10828) | 121(96–142) | 7313 (4989–9647) | ||||
| Disease status | ||||||||
| New diagnosis | 113 (90–141) | 0.001 | 6955 (5432–8717) | <0.001 | 101 (84–121) | <0.001 | 5637 (4474–7523) | <0.001 |
| Relapsing | 147 (130–173) | 9658 (6846–11311) | 129 (113–145) | 7434 (6166–9100) | ||||
| Diagnosis | ||||||||
| MPA | 132 (96–154) | 0.48 | 8202 (5558–9486) | 0.39 | 118 (94–131) | 0.54 | 7297 (5120–7921) | 0.82 |
| GPA | 137 (103–167) | 8535 (6005–10467) | 118 (101–141) | 6735 (5452–8715) | ||||
| Renal involvement | ||||||||
| Yes | 133 (102–159) | 0.66 | 8134 (5716–10113) | 0.39 | 119 (96–142) | 0.53 | 6888 (5089–8268) | 0.55 |
| No | 140 (102–175) | 8702 (6606–10362) | 114 (98–130) | 6792 (5861–8826) | ||||
| Correlation coefficientb | P- value | Correlation coefficient | P-value | Correlation coefficient | P-value | Correlation coefficient | P-value | |
| Age | −0.072 | 0.51 | 0.042 | 0.70 | −0.088 | 0.42 | 0.057 | 0.60 |
| BMI | 0.155 | 0.15 | 0.079 | 0.46 | 0.164 | 0.13 | 0.045 | 0.68 |
| BSA | −0.105 | 0.34 | −0.162 | 0.13 | −0.158 | 0.15 | −0.243 | 0.02 |
| BVAS/WG | −0.263 | 0.01 | −0.223 | 0.04 | −0.246 | 0.02 | −0.194 | 0.07 |
| B cells | −0.206 | 0.07 | −0.254 | 0.02 | −0.193 | 0.09 | −0.140 | 0.21 |
| Creatinine Clearance | −0.040 | 0.72 | −0.052 | 0.63 | −0.017 | 0.88 | −0.154 | 0.15 |
| Baseline IgG level | −0.227 | 0.035 | −0.122 | 0.258 | −0.233 | 0.032 | −0.153 | 0.157 |
a
Rituximab levels were compared between groups using Wilcoxon’s rank sum test. Rituximab levels are in μg/ml.
b
Correlations between rituximab level and continuous variables were assessed using Spearman’s test. AUC: area under the curve; BVAS/WG: Birmingham Vasculitis activity score for granulomatosis with polyangiitis (Wegener’s granulomatosis); GPA: granulomatosis with polyangiitis; MPA: microscopic polyangiitis; miRAMM: monoclonal immunoglobulin Rapid Accurate Mass Measurement; W2: week 2.