AB1211 A RETROSPECTIVE ANALYSIS OF LABORATORY ABNORMALITIES FOUND DURING METHOTREXATE MONITORING AND THE COST IMPLICATIONS

Abstract

Background Methotrexate (MTX) remains the first line treatment in majority of cases of inflammatory arthritis. The current British Society of Rheumatology (BSR) Guidelines suggest checking Full blood Count (FBC), ALT/AST, Albumin, Creatinine at 0,2,4,6,10,14, 18 weeks and then 12 weekly. Despite this close monitoring recommendation, MTX is generally considered a safe drug by Rheumatologists and its use has grown significantly over last two decades. Objectives To evaluate the incidence of liver, renal and haematological toxicities during Methotrexate treatment and calculate the cost implications. Methods 101 patients (30 males 71 females) (Age 40-89 year Mean 66.5 year) prescribed MTX were randomly selected and retrospective analysis was performed. 91 Rheumatoid arthritis, 8 Psoriatic arthritis and 2 patients had Undifferentiated Inflammatory Arthritis. 20 patients had Early Inflammatory Arthritis ( 100 U/l; unexplained reduction in albumin 105 fL, Neut 0.5 × 109/l and mild haematological toxicity (HM) was between normal and HS. Severe renal toxicity (RS) was defined as Creatinine increase >30% over 12 months and/or calculated GFR Results Over 1 year, 101 patients had total of 609 blood tests for MTX monitoring (Min 1 Max 17). FBC, Liver Function Test, Urea & Electrolytes, CRP and ESR each cost £8.54. LS was found in 4 patients, LM in 15, HM in 3 and RM in 2 patients. MTX was stopped in all 4 patients with LS. Mild toxicities (LM, HM and RM) recovered after close monitoring or reduction in dose. 5 patients with mild toxicities were on MTX for 1 year. All patients with severe and mild toxicities did not have any significant comorbidities compared to rest of the patients. It was calculated that detecting one LS cost (609x8.54)/4 = £1300.2. Similarly one LM cost £346.7, one HM £1733.6 and one RM £2600.43. These costs does not include travel expenses, parking charges and time off work for appointments in phlebotomy. Conclusion Our cohort shows that mild liver toxicity is the most commonly found abnormality during MTX monitoring and patients on stable doses still need monitoring for liver toxicity. Haematological and renal toxicities are much less common and a more relaxed monitoring schedule may be acceptable for these parameters. Regular monitoring for inflammatory markers (CRP, ESR) causes an extra cost burden. The direct cost for identifying each abnormality is considerable.