What are the implications of a high basophil percentage but normal basophil count in an older adult patient with a history of atrial fibrillation, currently on Eliquis (apixaban) anticoagulation therapy, who has recently experienced a fall?

High Basophil Percentage with Normal Absolute Basophil Count

A high basophil percentage with normal absolute basophil count is a relative basophilia caused by decreased numbers of other white blood cell types (relative shift), not a true increase in basophils, and requires no change to your current Eliquis anticoagulation regimen for atrial fibrillation.

Understanding the Laboratory Finding

• Relative basophilia occurs when the absolute basophil count remains within normal range (typically 0-200 cells/μL) but the percentage appears elevated due to reduction in other white cell populations, most commonly neutropenia or lymphopenia
• This is a mathematical artifact of calculating percentages from a reduced total white blood cell count, not a pathological increase in basophil production
• In the context of recent fall and possible infection/inflammation, this likely represents a transient reactive change in white cell distribution

Critical Management Priority: Continue Anticoagulation

Your Eliquis (apixaban) should be continued without interruption for atrial fibrillation stroke prevention. 1

• The FDA label explicitly warns that stopping apixaban increases stroke risk, and discontinuation should only occur after discussion with the prescribing physician 1
• Elderly patients (≥75 years) with atrial fibrillation have approximately 23.5% of ischemic strokes attributable to AF, making anticoagulation critically important 2
• Apixaban reduces stroke risk by 64-68% compared to aspirin or no treatment in atrial fibrillation patients 3

Post-Fall Bleeding Risk Assessment

Age alone does not contraindicate anticoagulation, even after a fall. 2

• The American College of Cardiology states that age per se is not a contraindication to anticoagulation in high-risk atrial fibrillation patients, as stroke prevention benefit exceeds bleeding risk in the vast majority of cases 2, 4
• The European Heart Rhythm Association emphasizes that a Markov decision model demonstrates patients would need to fall 295 times per year before the risk of subdural hemorrhage from falls outweighs the stroke prevention benefit of anticoagulation 2
• Elderly patients (≥75 years) have approximately twice the bleeding risk during anticoagulation compared to younger patients, but anticoagulation remains warranted when ischemic stroke risk exceeds bleeding risk 2

Verify Appropriate Apixaban Dosing

Standard dose is 5 mg twice daily; reduce to 2.5 mg twice daily only if ≥2 of the following criteria are met: 3

• Age ≥80 years
• Weight ≤60 kg
• Serum creatinine ≥1.5 mg/dL

Calculate creatinine clearance using Cockcroft-Gault formula to ensure appropriate dosing, as apixaban is partially renally cleared. 3, 5

Optimize Modifiable Bleeding Risk Factors

Blood pressure control is critically important to reduce both ischemic stroke risk and intracranial hemorrhage risk during anticoagulation: 3, 5

• Target blood pressure <140/90 mmHg, ideally <130/80 mmHg
• Poorly controlled hypertension is the most important modifiable risk factor for bleeding complications during anticoagulation 2

Avoid concomitant medications that increase bleeding risk: 3, 5, 1

• Do not add aspirin to apixaban—this doubles bleeding risk without providing additional stroke protection 3
• Completely avoid NSAIDs (ibuprofen, naproxen, etc.) 3, 5
• Review all medications for drug interactions, particularly verapamil, amiodarone, clarithromycin, and erythromycin 5

What to Monitor

The basophil finding itself requires no specific intervention but warrants investigation of the underlying cause:

• Review complete blood count with differential to identify which cell line is reduced (causing the relative basophil elevation)
• Assess for infection, particularly urinary or respiratory, which is common in elderly patients after falls 6
• Monitor for signs of bleeding as outlined in the apixaban medication guide: unusual bruising, prolonged bleeding, blood in urine or stool, severe headache, or dizziness 1

Calculate creatinine clearance at least annually (or more frequently after acute illness) to ensure appropriate apixaban dosing. 4, 5

Common Pitfalls to Avoid

• Do not discontinue apixaban due to fall risk—the stroke prevention benefit far outweighs subdural hemorrhage risk unless falls are occurring multiple times weekly 2, 4
• Do not add aspirin thinking it provides additional protection—it only increases bleeding without additional stroke benefit 3, 5
• Do not assume the basophil percentage elevation is clinically significant when the absolute count is normal—this is a relative change only
• Do not use age as a reason to withhold or stop anticoagulation—elderly patients derive the greatest absolute benefit from stroke prevention 2, 4