Background Laboratory tests during disease modifying antirheumatic drug (DMARD) therapy are necessary to ensure that certain adverse events are not present,1,2 but often are costly. Current guidelines on monitoring DMARD therapy are mostly derived by consensus.3
Objectives To assess the value and costs of routine laboratory tests for the detection of toxicity of DMARD-therapy in rheumatoid arthritis, and to find evidence-guided proposals concerning types and frequencies of such tests.
Methods Data were collected from the outpatient charts of 362 RA-patients during 1386 patient-years (DMARD type, dosage, duration, reason for discontinuation and all details of adverse events). Clinically relevant laboratory abnormalities (mainly ALAT, ASAT, CBC, creatinine, protein excretion) were analysed to assess the effectiveness of laboratory tests in detecting abnormalities induced by DMARDs. On this basis, proposals were derived and then tested using data from a validation cohort of 231 patients (986 patient years) from another rheumatic disease centre. Cost analyses were performed using a cost catalogue.
Results Abnormal results of laboratory examinations accounted for approx. 10% of DMARD discontinuations. All significant abnormalities occurred or were heralded during the first 4 months of therapy. It was concluded that laboratory examinations could be limited to a small number of variables for individual DMARDs and that after the initial 4 months of therapy screening frequencies could be significantly reduced. These conclusions were proved to be correct in 98.3% of the independent second patient cohort. Adhering to such strategy could save up to 86% of costs incurring compared to published recommendations for monitoring DMARD therapies.
Conclusion Only a limited number of laboratory tests are necessary for safety monitoring of patients on DMARDs. These tests need to be performed more frequently (monthly) only in the first four months of therapy, and if not revealing abnormal results, examinations can thereafter be reduced to two to four times per year. Thus, the costs of routine laboratory tests during DMARD therapy can be significantly decreased with no increase in the risk of overseeing adverse events.
Fries JF, Williams CA, Ramey D, Bloch DA. The relative toxicity of disease-modifying antirheumatic drugs. Arthritis Rheum. 1993;36:297–306
Wolfe F. Adverse drug reactions of DMARDs and DC-ARTs in rheumatoid arthritis. Clin Exp Rheumatol. 1997;15(Suppl 17):75–81
American College of Rheumatology Ad Hoc Committee on Clinical Guidelines. Guidelines for monitoring drug therapy in rheumatoid arthritis. Arthritis Rheum. 1996;39:723–31