Anticoagulation Counselling OSCE — Warfarin vs DOACs, INR Monitoring, and Sick Day Rules

Why Anticoagulation Counselling Is Examined

Anticoagulants are among the highest-risk medications in clinical practice and a leading cause of preventable hospital admissions due to bleeding. OSCEs examine anticoagulation counselling in communication stations — counselling a patient newly started on warfarin or a DOAC, explaining a change from warfarin to a DOAC, or advising on anticoagulation around a procedure. Examiners mark patient-centred explanations, safety-netting, and completeness of counselling content.

Overview — Warfarin vs DOACs

Warfarin Counselling — Key Points

INR and Monitoring

Explain INR:

"Warfarin thins the blood by blocking the formation of certain clotting proteins. We measure the INR — International Normalised Ratio — to check how well it is working. A normal INR is around 1. When you are taking warfarin for [atrial fibrillation / a blood clot / your heart valve], we want your INR to be between [target range]."

Target INR ranges:

Dose Adjustments

• Start at a low dose; INR checked frequently until stable (anticoagulation clinic)
• Increase dose if INR below target; decrease if above
• Never stop warfarin abruptly without medical advice

Food Interactions

Drug Interactions

• NSAIDs (including ibuprofen) — raise INR and increase bleeding risk — avoid; use paracetamol for pain
• Aspirin — additive bleeding risk; only take if prescribed
• Antibiotics — many raise INR (metronidazole, fluconazole, macrolides, ciprofloxacin)
• St John's Wort — lowers INR (enzyme inducer)
• Alcohol — raises INR; avoid excess; consistent moderate intake is acceptable

Sick Day Rules for Warfarin

• Continue warfarin during illness unless told otherwise
• Vomiting/diarrhoea reduces absorption — check INR sooner
• Fever increases warfarin sensitivity — check INR
• Contact clinic or anticoagulation service if unwell for more than 48 hours

DOAC Counselling — Key Points

Explaining DOACs

"These are newer blood thinners. Unlike warfarin, they work at a fixed dose and do not require regular blood test monitoring. They are at least as effective as warfarin for [your indication] and are easier to manage day-to-day."

Missed Doses

DOAC-Specific Counselling

• Rivaroxaban: must be taken with food (the evening meal) — absorption is significantly reduced without food
• Dabigatran: do not crush or open capsule (coating protects stomach); store in original blister pack (moisture-sensitive)
• Apixaban: can be crushed and mixed with water or apple juice (useful for patients with swallowing difficulty)

Signs of Bleeding — Safety Netting

Provide clear safety-netting for all anticoagulated patients:

Procedures and Anticoagulation

Before procedures, patients need guidance on interruption:

Frequently Asked Questions

"What is the reversal agent for warfarin?"

For non-urgent reversal: vitamin K (phytomenadione) 1-5 mg orally; takes 6-12 hours to work. For urgent reversal (major bleeding or emergency surgery): 4-factor prothrombin complex concentrate (PCC — Beriplex, Octaplex) 25-50 units/kg IV, which works within minutes, plus vitamin K 5-10 mg IV. Fresh frozen plasma (FFP) is less preferred due to volume load, slower effect, and risk of transfusion reactions.

"Which DOAC is safest in renal impairment?"

Apixaban has the least renal clearance (27%) and is generally preferred in moderate-to-severe renal impairment. Rivaroxaban requires dose reduction (15 mg OD instead of 20 mg OD if eGFR 15-49). Edoxaban requires dose reduction to 30 mg OD if weight below 60 kg, or eGFR 15-50. Dabigatran is predominantly renally excreted (80%) and should be avoided if eGFR below 30. All DOACs should be avoided if eGFR below 15.

"What should an anticoagulated patient do before a dental procedure?"

For simple extractions and most minor dental procedures: warfarin can usually be continued (discuss with dentist — local haemostatic measures are generally sufficient). NICE and the British Dental Association advise continuing warfarin for simple extractions if INR is within therapeutic range. For oral surgery under general anaesthetic or multiple extractions: temporary warfarin interruption may be needed — contact the anticoagulation clinic. For most DOACs: continue for minor procedures; pause 24-48 hours before more invasive procedures.

"How do you explain the difference between warfarin and a DOAC to a patient?"

"Both thin the blood to prevent clots, but they work differently. Warfarin has been used for decades, needs regular blood tests to check the dose, and is affected by what you eat and other medicines. The newer tablets — called DOACs — work in a more direct way, need a fixed dose, and don't require regular monitoring. They are at least as effective and some studies show they have a lower risk of certain types of bleeding — especially in the brain. If you have a mechanical heart valve, warfarin is still required. For most other reasons, either can be used and your doctor can help you decide which suits you best."

"What is time in therapeutic range (TTR) and why does it matter?"

TTR is the percentage of INR measurements that fall within the therapeutic range (typically 2.0-3.0) over a given period. A TTR above 70% is considered adequate anticoagulation control with warfarin. Below 65% indicates poor control — associated with increased stroke risk (when below range) and bleeding risk (when above range). Poor TTR is one of the indications for switching from warfarin to a DOAC. Anticoagulation clinics calculate TTR and use it to guide patient management.

Related Posts

• Atrial Fibrillation Management OSCE — CHA2DS2-VASc scoring and anticoagulation decisions in AF
• Pulmonary Embolism OSCE — anticoagulation duration and choice in PE
• Medication Review OSCE — reviewing anticoagulation as part of a comprehensive medication review