Daily practices regarding safety monitoring of low-dose methotrexate and comparison to guidelines: A population-based cohort study

Purpose. - To describe daily practices regarding safety monitoring of methotrexate prescribed at low-(i.e. <= 30mg/week). To identify determinants of these practices. To assess association between monitoring and early methotrexate discontinuation. Methods. - Population-based cohort study using the French claims database echantillon generaliste de beneficiair (EGB) over the period 2009-2015. Incident methotrexate users were included. The pre-treatment and post-treatment monitoring prescribed to these patients was analyzed. Determinants of monitoring were identified using a logistic regression model. Association between monitoring and early methotrexate discontinuation was assessed using Cox proportional-hazards model. Results. - During the study period, 615924 individuals had data in the EGB and 2472 (0.40%) were incident methotrexate users (63.3% women; mean age: 54.7 +/- 17.8 years; mean weekly dosage: 13.0 +/- 5.3mg). Among these incident users, only 50-70% had an albumin testing (67.0%); HIV (49.7%), hepatitis B (54.8%) or C (55.0%) serology; or chest X-ray (57.4%) within the year before initiating methotrexate. Only 65.7% had a least one CBC, transaminase and urea-creatinine testing combined within the three months before initiation. During the first three months of exposure, the median number of CBC, transaminase and urea-creatinine testing was 2 [1-4], 2 [1-4], and 2 [1-3], respectively. The monitoring modalities depend more on prescriber characteristics than on patient or treatment characteristics. There was a significant positive association between frequency of monitoring during exposure and early methotrexate discontinuation. Conclusion. - Monitoring of patients prescribed low-dose methotrexate is much less frequent than recommended. Frequent monitoring is associated with early methotrexate discontinuation. (C) 2019 Published by Elsevier Masson SAS on behalf of Societe francaise de pharmacologie et de therapeutique.