Corrected Count Increment (CCI) Calculator
Corrected Count Increment (CCI) Calculator
Work out whether a platelet transfusion actually worked. Enter counts in the unit your laboratory reports — the ×10⁹/L to /µL conversion the formula needs is done inside the calculator.
Corrected Count Increment (CCI)
Increment × BSA ÷ dosePre 12, post 32 ×10⁹/L; BSA 1.8 m²; 3 × 10¹¹ platelets transfused
Formula
Platelet increment (/µL) = (post-transfusion count − pre-transfusion count, in ×10⁹/L) × 1,000
- increment in /µL
- the formula is defined against a count per microlitre. A count of 20 × 10⁹/L is 20 × 10³/µL, which is 20,000/µL — the same number multiplied by a thousand. This calculator takes ×10⁹/L and converts internally
- body surface area
- corrects for the size of the recipient, because the same dose spreads through a larger blood volume in a larger patient
- dose in ×10¹¹
- the platelet content of the component, printed on the label — not the number of packs. Dividing by packs instead of by 10¹¹ inflates the CCI roughly threefold
- 7,500
- the threshold for a successful increment at 10–60 minutes, the version applied here. At 18–24 hours the corresponding figure is 4,500, and the two answer different questions
Worked example
Pre 12, post 32 ×10⁹/L; BSA 1.8 m²; 3 × 10¹¹ platelets transfused
Increment = 32 − 12 = 20 × 10⁹/L, which is 20 × 10³/µL, so 20,000/µL
20,000 × 1.8 = 36,000
36,000 ÷ 3 = 12,000
Above 7,500 on a count taken 10–60 minutes after transfusion — a successful increment
Had the increment been entered as 20 rather than converted, the CCI would have read 12 and every transfusion would look refractory
Which threshold, and what a failure tells you
| Sample timing | Successful CCI | A poor result points at |
|---|---|---|
| 10–60 minutes (the 1-hour CCI) | Above 7,500 | Immune destruction — HLA class I, or less often HPA, alloantibodies |
| 18–24 hours | Above 4,500 | Consumption: sepsis, splenomegaly, active bleeding, DIC, amphotericin B |
| Good at 1 hour, poor at 18–24 hours | — | Shortened survival rather than failed recovery, which is a non-immune picture |
| At or below 7,500 at 1 hour, on two consecutive ABO-compatible transfusions | — | Platelet transfusion refractoriness — send an HLA antibody screen |
The three quantities, and how each is reported
| Quantity | How it arrives | What the formula needs |
|---|---|---|
| Platelet increment | ×10⁹/L in the UK, ×10³/µL in the US — the same number | /µL: multiply the ×10⁹/L figure by 1,000 |
| Body surface area | m², from height and weight | m² — no conversion |
| Platelet dose | ×10¹¹ per component, on the label | ×10¹¹ — the platelet content, not the number of packs |
A number that separates destruction from consumption
A platelet transfusion that fails to raise the count is common, and the corrected count increment exists to say whether it genuinely failed or whether the patient was simply large and the dose small. It divides the rise in platelets by the number of platelets given and multiplies by body surface area, so a small increment after a small dose in a big adult is no longer confused with a real failure. Above 7,500 on a count taken 10 to 60 minutes after the transfusion, the increment is successful.
The units are where this calculation goes wrong. The equation is written for a platelet increment per microlitre, and a United Kingdom laboratory reports platelets in ×10⁹/L. Those are the same number in ×10³/µL, so an increment of 20 × 10⁹/L is 20,000/µL and must be multiplied by a thousand before it enters the formula. Skipping that step turns a perfectly good CCI of 12,000 into 12, and every transfusion on the ward looks refractory. This page takes counts in ×10⁹/L and does the conversion itself.
Timing is the second decision, and it is not a detail. A count at 10 to 60 minutes measures recovery: how many of the transfused platelets survived the first hour. A count at 18 to 24 hours measures survival, and has its own threshold of 4,500. Read together they separate the two families of cause. A poor one-hour CCI points at immune destruction, usually HLA class I alloimmunisation in a multiply transfused patient. A good one-hour CCI followed by a poor 24-hour one points at consumption — sepsis, splenomegaly, active bleeding, disseminated intravascular coagulation, or amphotericin B.
Refractoriness is a definition, not a single result. It requires a CCI at or below 7,500 one hour after two consecutive transfusions of ABO-compatible, fresh platelets, and the qualifiers matter: ABO-incompatible platelets and older components both give poorer increments in patients who are not alloimmunised at all. Only once those are excluded is an HLA antibody screen worth sending, and only then does HLA-selected or crossmatch-compatible product have anything to offer. Non-immune causes are far commoner, and no amount of HLA matching corrects them.
Frequently asked questions
What is a normal corrected count increment?
Above 7,500 on a count taken 10 to 60 minutes after the transfusion counts as a successful increment. At 18 to 24 hours the equivalent threshold is 4,500. Below those figures the transfusion has not achieved what it should, though a single poor result is not enough to diagnose refractoriness.
Do I enter the platelet count in ×10⁹/L or per microlitre?
Enter it in ×10⁹/L, the unit UK laboratories report. The formula needs the increment per microlitre, which is the same number multiplied by 1,000, and this calculator applies that conversion internally so you do not have to.
How is platelet transfusion refractoriness defined?
A corrected count increment at or below 7,500 one hour after each of two consecutive transfusions of ABO-compatible platelets. The ABO qualifier matters: incompatible or older components give poor increments in patients with no alloantibodies at all.
What does a good 1-hour CCI but a poor 24-hour CCI mean?
Consumption rather than immune destruction. The platelets circulated normally at first and were then used up — sepsis, splenomegaly, active bleeding, DIC or amphotericin B. HLA-selected platelets will not fix it; the underlying cause has to be treated.
Where do I find the platelet dose in ×10¹¹?
On the component label, which states the platelet content of the pack. Use that number, not the number of packs given. Dividing by packs instead of by the content in ×10¹¹ inflates the result roughly threefold for a standard adult dose.
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References
- Estcourt LJ, Birchall J, Allard S, et al. Guidelines for the use of platelet transfusions. Br J Haematol. 2017;176(3):365–394.
- Hod E, Schwartz J. Platelet transfusion refractoriness. Br J Haematol. 2008;142(3):348–360.
- Slichter SJ, Kaufman RM, Assmann SF, et al. Dose of prophylactic platelet transfusions and prevention of hemorrhage. N Engl J Med. 2010;362(7):600–613.