Platelet transfusion refractoriness

• Sepsis
• Fever
• Disseminated intravascular coagulation
• Splenomegaly
• Treatment of infection, antibiotics (vancomycin), antifungals (amphotericin B)
• Graft-versus-host disease
• Hepatic veno-occlusive disease
• Bleeding

• Age of platelet component[6][7]
• ABO mismatch between platelet component and recipient[6][7]
• Number of platelets within the component if platelet increment (PI) is used to calculate platelet refractoriness[6]
• Pathogen-reduced platelet component[8]

• Alloantibodies to platelet antigens
  • Human leucocyte antigen (HLA) antibodies
  • Human platelet antigen (HPA) antibodies
• Immune complexes
• Other antibodies
  • Drug-related antibodies

This is the simplest method, and only requires data on the platelet count before and after the transfusion.[9] The platelet increment is also known as the absolute count increment and count increment.[5][10]

PI = post-transfusion platelet count - pre-transfusion platelet count

However, it is affected by the number of platelets given in the transfusion (platelet dose) and the patient's blood volume. Larger patients and smaller platelet doses decrease the platelet increment.[2][9] These factors are adjusted for in the other methods of defining platelet refractoriness.[2][3][9]

A 1-hour post-transfusion PI of less than 5 to 10 x 10⁹/l is considered evidence of platelet refractoriness.[5][10] Due to lack of data on platelet dose this is often the only measure of platelet refractoriness that can be performed in routine clinical practice.[5]

Requires data on the platelet increment (PI), the patient's total blood volume (TBV) - estimated using the patient's weight multiplied by 0.075, and the number of platelets transfused (platelet dose)[10][11]

PPR = ((PI x TBV)/PD) x 100

At 1 hour post-transfusion, a PPR < 20% is considered evidence of platelet refractoriness.[5][10] At 16 hours post-transfusion a PPR < 10% is considered evidence of platelet refractoriness.[10]

PPI is very similar to the percentage platelet recovery (PPR) but there has been an additional adjustment for splenic pooling of platelets (PPR multiplied by 2/3)[5][11]

PPI = PPR/0.67 = ((PI / 0.67) x TBV)/PD x 100

This requires data on the platelet increment (PI, in platelets/µl), the patient's Body surface area (BSA, in m²), and the number of platelets transfused (PD, in 10¹¹).[5][10][11]

${\displaystyle {CCI}=PI*{\frac {BSA}{PD}}}$

For example, a PI of 25,000 platelets/µl, a BSA of 1.8m² and a PD of 4x10¹¹ gives a CCI of 11,250 platelets*m²/10¹¹µl

At 1 hour post-transfusion a CCI greater than 7500 indicates a sufficient post-transfusion increment, whereas a CCI less than 7500 is considered diagnostic of platelet refractoriness.[10] At 24 hours post transfusion a CCI less than 5000 suggests platelet refractoriness.[10]

Some blood banks maintain records of the estimated number of platelets in each unit.[5] Current requirements in the US stipulate that a unit of apheresis platelets must contain at least 3.0 x10¹¹ platelets.[12] In England only 1% of adult platelet components are tested to check the number of platelets meet the minimum required standard of 2.4 x 10¹¹ platelets.[13][14] Only components that contain fewer than 1.6 x 10¹¹ platelets are discarded.[13][14] This means that there can be a lot of variability in the number of platelets contained within each transfusion.[5]