Platelet Transfusion — Dose & CCI
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とは何か Platelet Transfusion Calculator?
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Platelet transfusion is the administration of donor platelets to patients with thrombocytopenia or platelet dysfunction to prevent or treat bleeding. Platelets are small anucleate cell fragments critical to primary haemostasis — they adhere to damaged vascular endothelium, activate, and aggregate to form a platelet plug before the coagulation cascade consolidates this into a fibrin clot. The standard adult therapeutic dose (ATD) consists of either 4–6 units of pooled buffy-coat-derived platelets or a single apheresis platelet unit, both providing approximately 250–350 × 10^9 platelets and raising the platelet count by 20,000–40,000/mcL in a 70 kg adult without refractoriness. Platelet transfusion thresholds depend on the clinical setting: prophylactic transfusion is given at counts <10,000/mcL in stable haematology patients and <20,000/mcL in those with fever or minor procedures; higher thresholds (50,000–100,000/mcL) are used for invasive procedures or surgery. The Corrected Count Increment (CCI) is the key metric for assessing transfusion efficacy: CCI = (Post-transfusion count − Pre-transfusion count) × BSA (m²) / (Platelets transfused × 10^11). A CCI greater than 7,500 at 1 hour post-transfusion indicates an adequate response. A CCI below 7,500 on two consecutive transfusions suggests platelet refractoriness, most commonly from HLA alloimmunisation, which requires HLA-matched or crossmatch-compatible platelets. Other causes of poor platelet increment include sepsis, splenomegaly, DIC, and fever. Understanding the CCI is essential for efficiently managing haemato-oncology patients on chronic platelet support.
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公式
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Dose: 1 Adult Therapeutic Dose (ATD) = 4–6 pooled units or 1 apheresis unit
CCI = (Post-platelet count − Pre-platelet count [/mcL]) × BSA (m²) / (Platelets transfused × 10^11)
CCI >7500 at 1 hour = adequate response
CCI <7500 on 2 consecutive occasions = platelet refractoriness変数の説明
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| 記号 | 名前 | 単位 | 説明 |
|---|---|---|---|
| CCI | Corrected Count Increment | dimensionless | Standardised measure of platelet transfusion efficacy; >7,500 at 1h = adequate |
| PLT_transfused | Platelets Transfused | x10^11 | Total platelet content of the unit(s) given; typically 3–4 × 10^11 per ATD |
方法 Platelet Transfusion Calculator
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- 1Confirm indication: thrombocytopenia with active bleeding, prophylactic threshold (<10,000/mcL stable, <20,000/mcL fever/procedure), or platelet dysfunction.
- 2Record pre-transfusion platelet count, patient weight, and body surface area (BSA) for CCI calculation.
- 3Order 1 ATD (4–6 pooled donor units or 1 apheresis unit). Request ABO-compatible platelets; Rh-negative platelets for Rh-negative females of childbearing age.
- 4Administer platelets over 15–30 minutes. Observe for transfusion reactions during and after infusion.
- 5Check post-transfusion platelet count at 1 hour and 24 hours to assess increment.
- 6Calculate CCI using the formula. CCI >7,500 at 1 hour = adequate response; CCI <7,500 = investigate refractoriness.
- 7If refractory: check for HLA antibodies, request HLA-matched or crossmatch-compatible platelets from the blood bank, and investigate for non-immune causes (DIC, sepsis, splenomegaly).
解いた例
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CCI >7,500 — excellent response; no refractoriness
The platelet count rose by 34,000/mcL and the CCI is well above the 7,500 threshold. This indicates normal platelet survival and no immune-mediated destruction. Standard dosing interval can be maintained.
CCI <7,500 — poor increment; refractoriness suspected
The minimal rise in platelet count despite a full ATD, with a CCI of only 1,943, is consistent with immune-mediated platelet destruction from HLA antibodies. HLA antibody screen should be requested and HLA-matched platelets sourced from the national blood service.
Transfuse shortly before surgery; recheck count immediately pre-operatively
For major surgery, a platelet count of at least 80,000/mcL is generally required. Each ATD raises count by approximately 20,000–40,000/mcL. Two ATDs given 30 minutes before surgery with immediate pre-operative count verification is the standard approach.
Low CCI without HLA antibodies — non-immune cause; treat underlying sepsis
Sepsis causes platelet consumption and splenomegaly traps transfused platelets, reducing the increment. As HLA antibodies are absent, immune refractoriness is excluded. Treating the infection is the priority; higher transfusion thresholds and more frequent transfusions may be temporarily needed.
実際の応用
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Haemato-oncology wards managing chemotherapy-induced thrombocytopenia with twice-weekly prophylactic platelet counts and transfusion thresholds., representing an important application area for the Platelet Transfusion in professional and analytical contexts where accurate platelet transfusion calculations directly support informed decision-making, strategic planning, and performance optimization
Intensive care units monitoring platelet consumption in DIC complicating sepsis, trauma, or obstetric emergencies., representing an important application area for the Platelet Transfusion in professional and analytical contexts where accurate platelet transfusion calculations directly support informed decision-making, strategic planning, and performance optimization
Cardiac surgical units transfusing platelets post-cardiopulmonary bypass to reverse bypass-induced platelet dysfunction and prevent re-operation for bleeding., representing an important application area for the Platelet Transfusion in professional and analytical contexts where accurate platelet transfusion calculations directly support informed decision-making, strategic planning, and performance optimization
Neonatal ICUs managing NAIT with HPA-matched platelets to prevent intracranial haemorrhage in affected neonates., representing an important application area for the Platelet Transfusion in professional and analytical contexts where accurate platelet transfusion calculations directly support informed decision-making, strategic planning, and performance optimization
Blood banks using CCI data to identify HLA-alloimmunised patients and coordinate procurement of compatible donor platelets for refractory cases., representing an important application area for the Platelet Transfusion in professional and analytical contexts where accurate platelet transfusion calculations directly support informed decision-making, strategic planning, and performance optimization
特殊なケース
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Immune Thrombocytopenic Purpura (ITP)
{'title': 'Immune Thrombocytopenic Purpura (ITP)', 'body': 'In ITP, platelet transfusion is generally ineffective because transfused platelets are rapidly destroyed by anti-platelet antibodies. Transfusion is reserved for life-threatening bleeding and given at high doses (2 ATDs) as a temporary measure. Specific treatments (IVIG, corticosteroids, thrombopoietin receptor agonists) are the mainstay of management.'}
Dengue Fever
{'title': 'Dengue Fever', 'body': 'Dengue causes a self-limiting thrombocytopenia rarely requiring transfusion unless the count falls below 10,000/mcL with active bleeding. Over-transfusion with platelets is associated with worse outcomes in dengue due to increased intravascular volume and potential immune activation. WHO guidelines advise against prophylactic platelet transfusion in dengue without clinical bleeding.'}
When platelet transfusion input values approach zero or become negative in the
When platelet transfusion input values approach zero or become negative in the Platelet Transfusion, mathematical behavior changes significantly. Zero values may cause division-by-zero errors or trivially zero results, while negative inputs may yield mathematically valid but practically meaningless outputs in platelet transfusion contexts. Professional users should validate that all inputs fall within physically or financially meaningful ranges before interpreting results. Negative or zero values often indicate data entry errors or exceptional platelet transfusion circumstances requiring separate analytical treatment.
Post-Cardiopulmonary Bypass
In the Platelet Transfusion, this scenario requires additional caution when interpreting platelet transfusion results. The standard formula may not fully account for all factors present in this edge case, and supplementary analysis or expert consultation may be warranted. Professional best practice involves documenting assumptions, running sensitivity analyses, and cross-referencing results with alternative methods when platelet transfusion calculations fall into non-standard territory.
Thrombotic Microangiopathy (TMA)
In the Platelet Transfusion, this scenario requires additional caution when interpreting platelet transfusion results. The standard formula may not fully account for all factors present in this edge case, and supplementary analysis or expert consultation may be warranted. Professional best practice involves documenting assumptions, running sensitivity analyses, and cross-referencing results with alternative methods when platelet transfusion calculations fall into non-standard territory.
Platelet Transfusion reference data
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| Clinical Setting | Platelet Threshold | Target Count | Notes |
|---|---|---|---|
| Stable haematology patient (prophylactic) | <10,000/mcL | >10,000/mcL | Single ATD; restrict to once daily |
| Fever or minor bleeding | <20,000/mcL | >20,000/mcL | More frequent monitoring |
| Central line insertion / minor procedure | <50,000/mcL | >50,000/mcL | Give shortly before procedure |
| Major surgery / epidural | <80,000/mcL | >80,000/mcL | Recheck immediately pre-operatively |
| Neurosurgery / intracranial procedure | <100,000/mcL | >100,000/mcL | Consider continuous monitoring |
| Active major bleeding | Any count | >50,000–100,000/mcL | Give empirically in massive haemorrhage protocol |
よくある質問
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What is the difference between pooled and apheresis platelets?
Pooled platelets are made by combining buffy coats from 4–6 whole blood donations. Apheresis (single-donor) platelets are collected from one donor using a cell separator. Both provide a similar platelet dose per ATD. Apheresis units reduce donor exposure (lower alloimmunisation risk), are preferred for HLA-matched products, and are the format of choice for neonatal or immunocompromised patients.
What is the 24-hour CCI used for?
The 24-hour CCI reflects platelet survival rather than the initial distribution. A low 1-hour CCI with a reasonable 24-hour CCI suggests immune destruction occurring rapidly post-transfusion. A low 24-hour CCI with a normal 1-hour CCI is more consistent with non-immune consumption (sepsis, DIC). Both time points together provide a more complete picture.
What platelet count thresholds typically trigger a transfusion?
Platelet transfusion thresholds vary based on the patient's clinical situation and risk of bleeding. For prophylactic transfusions in stable, non-bleeding patients, a common threshold is <10,000/µL. In patients undergoing invasive procedures or with active bleeding, higher thresholds like <20,000/µL or <50,000/µL, respectively, are often targeted to ensure adequate hemostasis.
How much does a standard platelet transfusion typically increase the patient's platelet count?
A standard adult dose of apheresis platelets (typically 3.0-4.0 x 10^11 platelets) is expected to increase the recipient's platelet count by approximately 20,000-40,000/µL (20-40 x 10^9/L) one hour post-transfusion. This increment can be lower in patients with factors like fever, sepsis, splenomegaly, or ongoing bleeding. The actual response is often evaluated using the Corrected Count Increment (CCI).
What defines platelet refractoriness in patients receiving transfusions?
Platelet refractoriness is characterized by a suboptimal post-transfusion platelet count increment, despite transfusing an adequate dose of viable platelets. It is commonly defined by a 1-hour or 24-hour Corrected Count Increment (CCI) of less than 7,500 (or sometimes <5,000) on two separate occasions. This condition can be due to immune causes, such as HLA alloimmunization, or non-immune factors like sepsis, disseminated intravascular coagulation, or splenomegaly.
避けるべきよくある間違い
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- !Transfusing platelets in HIT or TTP where platelet transfusion is contraindicated and may cause life-threatening thrombosis.
- !Using a platelet count alone to assess response without calculating the CCI — a low absolute increment in a large patient may still represent a clinically adequate response.
- !Not timing the post-transfusion count correctly — the 1-hour count must be taken exactly at 1 hour post-completion for a valid CCI.
- !Failing to investigate non-immune causes of low CCI (fever, sepsis, DIC, splenomegaly) before committing to expensive HLA-matched platelets.
- !Giving platelets prophylactically above the evidence-based threshold in stable patients — most guidelines do not recommend prophylaxis above 10,000/mcL in uncomplicated thrombocytopenia.
- !Ignoring Rh status in females of childbearing age — failure to give anti-D after Rh-incompatible platelet transfusion can cause haemolytic disease of the foetus/newborn in future pregnancies.
プロのヒント
When platelet refractoriness is suspected, always calculate the CCI from the 1-hour post-transfusion count and look for both immune and non-immune causes before ordering expensive HLA-matched products. Correcting reversible non-immune factors (treating sepsis, reviewing potentially causative drugs, addressing DIC) is cost-effective and may restore adequate increments without specialist products.
ご存知でしたか？
Platelets were only recognised as distinct cellular elements of blood in the 1880s by Giulio Bizzozero, who coined the term 'blood platelets'. Before this discovery, the clotting mechanism was attributed entirely to red blood cells. The first platelet transfusion was not performed until 1910, and platelet concentrates as a routine blood product only became available in the 1950s.
参考文献
- ›BCSH Guidelines for the use of platelet transfusions. Br J Haematol. 2003;122(1):10-23.
- ›Kaufman RM et al. Platelet Transfusion: A Clinical Practice Guideline from the AABB. Ann Intern Med. 2015;162(3):205-213.
- ›Slichter SJ. Platelet refractoriness and alloimmunization. Leukemia. 1998;12(Suppl 1):S51-55.
- ›NHS Blood and Transplant. Platelet transfusion — clinical and laboratory guidance. 2021.
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