How much does a single adult apheresis platelet unit increase the recipient's platelet count?

Platelet Increment from Single Apheresis Unit

A single adult apheresis platelet unit increases the recipient's platelet count by approximately 30,000–50,000/µL (or 30–50 × 10⁹/L) in a standard 70-kg adult. 1, 2

Expected Increment Details

Standard Response

• One apheresis unit contains 3–4 × 10¹¹ platelets suspended in 150–450 mL of plasma 3, 2, 4
• The expected increment is approximately 10,000/µL per apheresis unit when using simplified calculations 1
• More precisely, the increment should be >30 × 10⁹/L per apheresis unit in adults without complicating factors 1, 2

Calculating Expected Response

• The Corrected Count Increment (CCI) provides the most accurate assessment of transfusion adequacy 1, 2
• CCI formula: (post-transfusion platelet increment × body surface area in m²) / (number of platelets transfused × 10¹¹) 1
• A CCI ≥ 5,000 defines a satisfactory response to platelet transfusion 1, 2, 4

Timing of Post-Transfusion Count

• Obtain platelet count 10–60 minutes after transfusion ends to assess response 1
• A 10-minute draw is logistically convenient and yields equivalent results to a 1-hour measurement 1
• Always check the count before any invasive procedure to confirm hemostatic platelet levels have been achieved 1

Clinical Factors That Reduce Expected Increment

Common Causes of Poor Response

• Sepsis and active infection significantly diminish the expected platelet increment 1, 2
• Splenomegaly reduces increment by approximately 33% (normal splenic pooling) 1
• Disseminated intravascular coagulation (DIC) and massive hemorrhage consume transfused platelets rapidly 1, 2
• ABO incompatibility (e.g., A-type platelets to O-type recipient) markedly reduces recovery 1, 2
• Alloimmunization (HLA antibodies) accounts for ~90% of refractory cases 1

Trauma and Critical Illness

• In trauma with massive transfusion, one standard adult platelet dose may increase count by only 5–10 × 10⁹/L 1
• In cirrhosis patients, transfusion produces only a small increase in platelet count 1

Defining Inadequate Response and Refractoriness

When to Suspect Refractoriness

• Platelet refractoriness should only be diagnosed after ≥2 consecutive ABO-compatible transfusions (stored <72 hours) that fail to achieve adequate increments 1, 2
• Failure is defined as CCI <5,000 or absolute increment <2,000/µL per unit on both occasions 1
• If post-transfusion platelet count remains at or below the trigger level that prompted transfusion, administer additional platelet units 1

Investigation of Poor Response

• Upon confirmation of refractoriness, investigate underlying causes and coordinate with blood bank for targeted transfusion strategy 1
• Ensure ABO compatibility when evaluating for refractoriness, as incompatibility alone can diminish increments 1, 2
• Confirm platelet units were stored <72 hours before attributing poor response to true refractoriness 1

Critical Pitfalls to Avoid

• Never proceed with invasive procedures without laboratory confirmation that a hemostatic platelet count has been achieved 1
• Do not label a patient refractory after a single poor increment; require at least two consecutive inadequate responses 1
• Platelet count alone should not dictate transfusion decisions when platelet function is impaired—bleeding can occur despite normal counts 4
• Doubling the standard dose does not reduce bleeding risk compared to standard dose but increases costs and donor exposure 2, 4