[Patient safety in the treatment of rheumatic diseases : Laboratory monitoring in methotrexate treatment]. / Patientensicherheit in der Rheumatherapie : Labormonitoring bei Methotrexat.

BACKGROUND: Methotrexate (MTX) is the most commonly prescribed disease-modifying drug in the treatment of rheumatic diseases. Regular laboratory testing is recommended to recognize side effects, such as hepatotoxicity and myelotoxicity as well as decreases in renal function that may cause toxic MTX accumulation. Additionally, folic acid is recommended as prophylaxis against specific side effects. In this study we investigated whether laboratory monitoring and prescription of folic acid took place according to published recommendations. MATERIAL AND METHODS: Claims data from the statutory health insurance from 1 January 2009 to 31 December 2013 were retrospectively analyzed. A total of 40,087 adults with a rheumatic diagnosis (ICD10 codes M05-M18), no malignant disease and no previous MTX prescription within 12 months were extracted from the InGef (Institute for Applied Health Research in Berlin, formerly Health Risk Institute) research database. The frequency of recommended laboratory testing, appointments with rheumatologists and the prescription of folic acid prophylaxis were investigated. RESULTS: Of the patients 12,451 began treatment with MTX in the observation period. Between 42% and 46% of recommended blood counts, liver values and kidney function tests and 14% of urinalyses were performed according to recommendations. Of the patients 84% were seen regularly by a rheumatologist and 74% received a prescription for prophylactic folic acid. Serious conditions potentially resulting from MTX treatment were observed in 0.7-3.5 cases/1000 person years. DISCUSSION: Laboratory monitoring in the context of MTX treatment is carried out less frequently than recommended in the literature. Potential MTX-associated serious complications are rare from a practice perspective. On the one hand solutions are needed for a better coordination of laboratory monitoring. On the other hand more empirical evidence is needed regarding the benefits of laboratory monitoring and the appropriate intervals thereof.