Treatment: leflunomide, sulfasalazine, azathioprine, mycophenolate (tests before treatment and monitoring)

Laboratory tests

• FBC with platelets
• Serum creatinine with eGFR
• AST
• ALT
• Serum albumin
• Hepatitis B serology (HBsAg, anti-HBc, anti-HBs)
• Hepatitis C serology
• TPMT phenotyping or genotyping (azathioprine)if neededBefore any azathioprine: recommended by the SmPC ^[2] and by the BSR ^[3]. Outside the French fee schedule (no NABM code) ^[4].
• EBV serology (azathioprine, especially in inflammatory bowel disease)if needednon-French guidelineBefore a thiopurine: ECCO suggests looking for past EBV infection; in a seronegative patient, consider avoiding the thiopurine (risk of severe primary infection and lymphoproliferation); no comparative data prove the benefit of this screening ^[5].
• G6PD (sulfasalazine)if neededBefore sulfasalazine: G6PD deficiency is a contraindication (risk of haemolysis) ^[6]. None of the sources cited requires routine testing: to be done at least if origin or history is suggestive.
• Proteinuria: urine dipstick (sulfasalazine)if neededOn sulfasalazine, renal function is monitored by creatinine and proteinuria ^[6]: a baseline value is useful.
• Serum β-hCG (leflunomide; woman of childbearing potential)if neededLeflunomide: pregnancy must be excluded before treatment ^[7].
• Serum β-hCG, two tests 8-10 days apart (mycophenolate; woman of childbearing potential)if neededMycophenolate: two negative pregnancy tests (sensitivity ≥ 25 mIU/mL), the second 8 to 10 days after the first ^[8].
• HIV serology (with the patient's consent)if needednon-French guidelineThe BSR (2025) screens for HIV in every adult starting a disease-modifying treatment, except on hydroxychloroquine ^[3]. EULAR suggests considering this screening before conventional disease-modifying treatments and immunosuppressants ^[9].
• IGRA (QuantiFERON), or tuberculin skin testif neededLeflunomide: the SmPC requires a search for latent tuberculosis in all patients ^[7]. For other conventional disease-modifying treatments, the BSR looks for it if the risk is increased ^[3] and EULAR suggests considering it ^[9]. Not reimbursed in France for this indication ^[4].
• Varicella serology (anti-VZV IgG), if no history of varicellaif neededNo history of chickenpox or doubtful history: vaccinate if serology is negative, at least 6 weeks before treatment ^[10]. Reimbursed in France before long-term immunosuppressive treatment ^[4].
• Leflunomide: blood pressure (and weight) before treatment.

Every week for the first 8 weeks

• FBC with platelets

Every month for 3 months

• AST
• ALT
• Serum creatinine with eGFRif neededThe BSR includes creatinine in the monitoring of all disease-modifying treatments ^[3]; the SmPC does not ask for it routinely ^[2].

Then every 1 to 3 months

• FBC with platelets
• AST
• ALT
• Serum creatinine with eGFRif needednon-French guidelineBSR “standard” monitoring, every 3 months after initiation ^[3].

Every 2 weeks for 6 months

• FBC (with platelets and differential)
• ALT

Then every 8 weeks

• FBC (with platelets and differential)
• ALT
• Serum creatinine with eGFRif neededBSR “standard” monitoring (FBC, GFR, transaminases, albumin) ^[3]; the SmPC asks only for FBC and ALT ^[7].
• Serum albuminif neededBSR “standard” monitoring (FBC, GFR, transaminases, albumin) ^[3]; the SmPC asks only for FBC and ALT ^[7].
• Blood pressure and weight at every check.

Every 2 weeks for 3 months

• FBC with platelets
• AST
• ALT

Every month from the 4th to the 6th month

• FBC with platelets
• AST
• ALT

Then every 3 months

• FBC with platelets
• AST
• ALT
• Serum creatinine with eGFR
• Proteinuria: urine dipstick

Every week in the 1st month

• FBC with platelets

Twice a month in the 2nd and 3rd months

• FBC with platelets

Then every month until 1 year

• FBC with platelets
• Serum creatinine with eGFRif neededBSR “standard” monitoring for all disease-modifying treatments ^[3]; the SmPC details only FBC ^[8].
• ASTif neededBSR “standard” monitoring for all disease-modifying treatments ^[3]; the SmPC details only FBC ^[8].
• ALTif neededBSR “standard” monitoring for all disease-modifying treatments ^[3]; the SmPC details only FBC ^[8].
• Serum albuminif neededBSR “standard” monitoring for all disease-modifying treatments ^[3]; the SmPC details only FBC ^[8].
• Serum immunoglobulins (if recurrent infections)if neededRecurrent infections on mycophenolate: immunoglobulin measurement recommended (hypogammaglobulinaemia reported) ^[8].