Screen before you prescribe — immunosuppressive and biologic therapy

Station status

This is one MedVellum formative structured clinical encounter. The scoring, prompts and performance descriptions are educational feedback tools. They are not an official college station, timing, mark allocation, pass score or reproduced examination format. The encounter assesses the safe initiation of methotrexate in juvenile idiopathic arthritis, the pre-biologic screen before a tumour necrosis factor inhibitor, the weekly-versus-daily distinction, folic acid, monitoring, the live-vaccine rule, and family communication. [5] [9]

Candidate instructions

You are the paediatric registrar in a rheumatology joint clinic with a child about to start methotrexate for juvenile idiopathic arthritis. Establish the dose schedule, the folic acid plan, and the monitoring. Then address the family's questions, the live-vaccine timing, and the plan for escalation to a biologic if the methotrexate does not control the disease. Speak directly to the child and parent. State what you would assess or prescribe; do not perform painful manoeuvres on the actor. [1] [5]

Room setup and observable starting state

The encounter. Maya is six and sits with her mother in the rheumatology clinic. The consultant has just confirmed that methotrexate will be started for polyarticular juvenile idiopathic arthritis not controlled by an intra-articular corticosteroid and a non-steroidal agent. The candidate is asked to set out the regimen and the safeguards. The candidate should state the once-weekly schedule, the folic acid on the non-methotrexate days, the baseline and on-treatment bloods, and the family advice on the methotrexate day and missed doses. [1] [5]

Simulation safety. Maya remains seated throughout and is never examined painfully. Cards or the assessor supply the blood results and the immunisation record. The parent does not obstruct the consultation. [5]

Actor cues

Parent actor

• Begin with, "We've heard a lot about methotrexate and we're nervous." If asked what worries her, answer: "Is it chemotherapy? Will she lose her hair? Do we give it every day?"
• On the methotrexate day, ask: "What if she's sick on the methotrexate day — do we give two the next day?"
• On vaccines, ask: "She's due for her preschool boosters. Can she still have them?"
• On escalation, ask: "What happens if the methotrexate doesn't work?" [5]

Child actor

• Responds shyly to questions about stiffness: "It's hard to get moving in the morning, especially my knees." [1]

Assessor cues and clinical data

Release findings as the candidate reaches each step. Reward the weekly schedule, the folic acid, the monitoring plan, and the safeguard against daily dosing. [5]

Step 1 — The methotrexate regimen

Expected strong behaviour: state methotrexate once weekly at about 10 to 15 mg/m², by mouth initially, subcutaneous once the oral dose rises above about 12 to 15 mg/m² or for nausea; prescribe folic acid on the non-methotrexate days; explain that this is a low anti-inflammatory dose, not cancer chemotherapy, so hair loss is not expected; teach a single marked methotrexate day and never double up a missed dose. [1] [5]

Step 2 — Baseline and on-treatment bloods

Baseline full blood count, liver enzymes and creatinine, repeated soon after starting and then roughly every four to twelve weeks. Expected strong behaviour: name the panel and the interval, and state the reasons to hold the next dose — falling neutrophils, rising alanine aminotransferase, or new mouth ulceration. [5]

Step 3 — The live-vaccine rule

Immunisation record shows the second measles-mumps-rubella dose is overdue and varicella immunity is uncertain. Expected strong behaviour: complete the live vaccines before any biologic is started, because live vaccines are contraindicated on biologic therapy; inactivated influenza can be given on methotrexate. [11]

Step 4 — Escalation to a tumour necrosis factor inhibitor

Six months later the arthritis is still active, and a biologic is planned. Expected strong behaviour: state the pre-biologic screen — latent tuberculosis with both a tuberculin skin test and an interferon-gamma release assay, plus chest X-ray if positive or risk present, hepatitis B (surface antigen, core and surface antibody), hepatitis C, HIV, and varicella immunity; treat any latent tuberculosis with chemoprophylaxis before the first dose. [9] [10]

Step 5 — The sick-day advice

Expected strong behaviour: give the family clear advice — if Maya is febrile or unwell, seek urgent review; hold the next methotrexate or biologic dose during significant intercurrent illness; and recheck the bloods if there is mouth ulceration, a sore throat, or unexpected bruising. [10]

Marking domains

Debrief prompts

• What is the single most important prescribing safeguard on methotrexate, and how did you teach it to the family?
• Which pre-biologic test is non-negotiable, and why is it dual rather than single?
• How did you balance reassurance about methotrexate with the real need for monitoring and sick-day vigilance?
• If the family refused the biologic screen, how would you handle the conflict between safety and disease control? [5] [9]