Erythrocyte-methotrexate and disease activity in children treated with oral methotrexate for juvenile chronic arthritis

The concentration of methotrexate (MTX) in erythrocytes (E-MTX) was measure d twice with three months interval in 21 children suffering from juvenile c hronic arthritis (JCA). At the same time joint score, visual analogue scale NAS), and laboratory parameters (CRP. WBC, PMNs. and ALAT) were obtained. There was only a weak insignificant correlation between the dose of MTX/m(2 ) and E-MTX (r = 0.24, p=0.11). No significant relations between the clinic al or laboratory parameters and E-MTX was found. However, ALAT above normal range was associated with a lower dose of MTX (p = 0.02) and lower VAS (p = 0.02), indicating that toxicity may be associated with less articular dis comfort. At present we consider routine determination of E-MTX in children with JCA of limited value.