METHOTREXATE INTOLERANCE IN CHILDREN WITH JUVENILE IDIOPATHIC ARTHRITIS ACCORDING TO THE METHOTREXATE INTOLERANCE SEVERITY SCORE (MISS) QUESTIONNAIRE: A SINGLE-STAGE STUDY

Juvenile idiopathic arthritis (JIA) is the most common rheumatic disease in childhood. First-line therapy is the prescription of Methotrexate (MTX) though this drug can cause undesirable effects which in its turn dictates the need for the use of diagnostic techniques that would allow early detection of intolerance to MTX. One of such diagnostic approaches is the Methotrexate Intolerance Severity Score (MISS) questionnaire. The purpose of this research was to evaluate the frequency of MTX intolerance in children with JIA using the Russian-language adaptation of the MISS questionnaire. Materials and methods used: a single-center, single-stage study of children aged 3 to 17 y/o with a non-systemic variant of JIA who were prescribed MTX was conducted using the 2011 MISS questionnaire in Russian. The MTX intolerance was determined if the patient scored 6 points and above. Results: 250 patients (78 boys and 172 girls) were included in the study. MTX intolerance using the MISS questionnaire was identified in 30% of patients; the most common complaint was MTX-associated nausea. The cut-off point for the questionnaire was estimated using the ROC analysis. The area under the ROC curve was 0.945. Patients scoring 6 points with a sensitivity of 94% (95% CI 78-97) and specificity of 100% (95% CI 80-100) were intolerant to MTX. The validity of using the questionnaire to identify individuals with MTX intolerance has been demonstrated therefore the questionnaire can be recommended for wider use. Conclusion: MTX intolerance, which was determined by the total score (6 points and above) was identified in 75 patients on MTX therapy.