This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.
Checking that a platelet transfusion worked
Patients with very low platelet counts, from chemotherapy, leukemia, bone marrow failure or major surgery, often receive platelet transfusions to prevent or stop bleeding. Some of them stop responding: the platelet count barely rises after each transfusion. This platelet refractoriness is common in patients who receive many transfusions and needs to be recognized early.
A simple rise in the count is hard to interpret because it depends on the patient’s size and the number of platelets in the bag. The corrected count increment adjusts for both.
The formulas
CCI = (post-transfusion count − pre-transfusion count) × body surface area ÷ platelets transfused
with counts per µL, body surface area in m² and the dose in units of 10¹¹ platelets.
Percent platelet recovery = increment × blood volume ÷ platelets transfused × 100
using a blood volume of about 70 mL per kg.
Example
A patient 5 ft 9 in tall and 180 lb (body surface area 1.99 m²) has 10,000 platelets/µL before and 30,000/µL one hour after a transfusion of 3.0 × 10¹¹ platelets:
- Increment: 20,000/µL
- CCI = 20,000 × 1.99 ÷ 3.0 ≈ 13,300
- Percent recovery ≈ 38%
Both values show an adequate response.
Interpretation
| Timing | Poor response |
|---|---|
| 10 to 60 minutes after | CCI below 7,500 or recovery below 30% |
| 18 to 24 hours after | CCI below 5,000 or recovery below 20% |
Refractoriness is usually defined as two consecutive transfusions with a poor 1-hour response, ideally using fresh ABO-compatible platelets.
Finding the cause
- Poor 1-hour response: suggests an immune cause, mainly antibodies against HLA class I antigens, more rarely against platelet-specific antigens. Testing for these antibodies guides the choice of HLA-matched or crossmatched platelets.
- Good 1-hour response but poor 24-hour count: suggests faster consumption from fever, infection, bleeding, disseminated intravascular coagulation, an enlarged spleen or certain drugs.
Limits
Platelet counts at very low levels are less precise, and the dose in each product is an estimate unless measured. Results should always be read together with bleeding signs and the clinical situation, under the guidance of the hematology and transfusion teams.