Corrected Count Increment Calculator

Timing	CCI range	Classification
1 hour	≥ 7,500	Adequate response
1 hour	5,000 – 7,499	Borderline — repeat before diagnosing refractoriness
1 hour	< 5,000	Poor response — possible refractoriness
18–24 hour	≥ 4,400	Adequate response
18–24 hour	2,500 – 4,399	Borderline
18–24 hour	< 2,500	Poor response — possible refractoriness

Category	Common causes
Non-immune (more common)	Fever, sepsis, DIC, splenomegaly, active bleeding, graft-versus-host disease
Immune	HLA or platelet-specific alloimmunization from prior transfusion or pregnancy

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Walk-through

How to Use This Calculator

4 steps

1

Enter the platelet counts and dose

Type the pre-transfusion and post-transfusion platelet counts in ×10³/µL, the patient's body surface area in m², and the platelets transfused in ×10¹¹ (one apheresis unit ≈ 3.0×10¹¹; one pooled unit ≈ 0.55×10¹¹).

2

Pick the sample timing

Select whether the post-transfusion count was drawn at 1 hour or at 18-24 hours. The adequate-response threshold is different for each window, so this choice determines which cutoff the classification uses.

3

Read the CCI and classification

The hero shows the CCI and whether it is an adequate, borderline, or poor response for the selected timing. Open the Interpretation tab for the full reference table and the refractoriness workup.

4

Need a BSA? Estimate it

If you don't have a measured BSA, switch to the BSA Estimate tab, enter height and weight, and click "Use this BSA" to copy the Mosteller estimate straight into the CCI tab.

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Reference

Formula & Methodology

1 formula

Corrected count increment (CCI)

CCI = [(post - pre platelet count, /µL) x BSA (m^2)] / platelets transfused (x10^11)

Pre and post platelet counts are entered in x10^3/µL and scaled to cells/µL before the increment is taken. BSA is in m^2. Platelets transfused is in x10^11 — a standard apheresis unit contains roughly 3.0x10^11 platelets, a pooled/random-donor unit roughly 0.55x10^11. Multiplying the raw increment by BSA and dividing by the dose transfused standardizes the response so it can be compared across patients and transfusions of different size.

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High YMYL

Trust, Methodology & Sources

Reviewed by Calculover Editorial Review · Updated 2026-07-23 · 3 sources

Editorial accountability

Author: Quinn Sumner - Editor

Owner: Quinn Sumner - Editorial owner

Reviewer: Calculover Editorial Review - Clinical-source review

Last reviewed: 2026-07-23

Last verified: 2026-07-23

Data effective: 2026-07-23

Methodology

The calculator implements CCI = [(post-transfusion platelet count − pre-transfusion platelet count, cells/µL) × BSA (m²)] / (platelets transfused, ×10¹¹). Platelet counts are entered in ×10³/µL and scaled internally to cells/µL. BSA can be entered directly or estimated with the Mosteller formula (BSA = sqrt(height_cm × weight_kg / 3600)). The result is classified against commonly cited response thresholds for the 1-hour window (adequate ≥7,500; poor <5,000) and the 18-24 hour window (adequate ≥4,400; poor <2,500), based on MDCalc's CCI calculator and standard blood-bank reference tables.

Assumption: Platelet counts are entered in ×10³/µL (thousands per microliter), matching standard US lab reporting, and platelets transfused is entered in ×10¹¹.

Assumption: The post-transfusion count was drawn at the timing selected (1 hour or 18-24 hours); mixing up the timing window changes which threshold applies.

Assumption: The transfused platelets are assumed ABO-compatible and fresh (<72 hours old) for the refractoriness-workup guidance to apply as described.

Limitations & guidance

Exact adequate-response and refractory cutoffs vary somewhat between sources (MDCalc, blood-bank reference tables, and the original clinical literature); this tool uses commonly cited values, not a single universally agreed number.

A single low CCI does not diagnose platelet refractoriness — that requires ≥2 consecutive inadequate responses to ABO-compatible, fresh platelets, with non-immune causes (fever, sepsis, DIC, splenomegaly, bleeding) excluded first.

This calculator screens for an inadequate response; it does not identify the underlying cause. Platelet antibody testing (HLA and platelet-specific) is required to confirm alloimmunization.

Professional guidance: This calculator is for education only and is not medical advice, diagnosis, or treatment. A CCI result is a screening estimate, not a diagnosis, and does not replace the judgment of a licensed clinician evaluating the full clinical picture.

Primary sources

MDCalc — Corrected Count Increment (CCI) for Platelet Transfusion

Bishop JF, Matthews JP, McGrath K, et al. Factors influencing 20-hour increments after platelet transfusion. Transfusion. 1991;31(5):392-396.

Nahirniak S, Slichter SJ, Tanael S, et al. Platelet transfusion refractoriness: how do I diagnose and manage? Hematology Am Soc Hematol Educ Program. 2020;2020(1):527-533.

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Glossary

Key Terms Explained

7 terms

CCI Corrected count increment — the standard measure of how well a platelet transfusion raised the platelet count, adjusted for the patient's body surface area and the dose of platelets transfused.

Corrected count increment The full name for CCI: [(post-transfusion count − pre-transfusion count) × BSA] / platelets transfused. It removes the effect of patient size and transfusion dose so responses can be compared consistently.

Platelet refractoriness A pattern of consistently inadequate platelet increments after transfusion — formally, ≥2 consecutive low CCI values (or low percent platelet recovery) with ABO-compatible, fresh platelets, after non-immune causes have been excluded.

BSA Body surface area, in m². Used to scale the raw platelet increment because a fixed platelet dose raises the count less in a larger patient. Can be measured directly or estimated from height and weight (e.g., the Mosteller formula).

Platelet transfusion Infusion of donor platelets, most often as an apheresis unit (~3.0×10¹¹ platelets from a single donor) or a pooled/random-donor unit (~0.55×10¹¹ platelets, usually pooled from multiple donors).

Alloimmunization Development of antibodies against HLA or platelet-specific antigens on donor platelets, usually from prior transfusions, pregnancy, or transplantation. The immune cause of platelet refractoriness, confirmed by platelet antibody testing once non-immune causes are ruled out.

1-hour vs 18-24-hour CCI The two conventional post-transfusion sampling windows. The 1-hour CCI reflects the immediate increment; the 18-24 hour (sometimes reported as 20-hour) CCI reflects how well that increment held and is more sensitive to non-immune platelet consumption such as fever, bleeding, or splenomegaly.

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Scenarios

Real-World Examples

3 worked examples

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Adequate response to an apheresis unit

Pre 15, post 45, BSA 1.8, 1 apheresis unit — 1 hour

Pre-transfusion platelet count 15 x10^3/µL Post-transfusion platelet count 45 x10^3/µL Body surface area 1.8 m^2 Platelets transfused 3.0 x10^11

The count rose by 30 x10^3/µL (30,000/µL). CCI = 30,000 x 1.8 / 3.0 = 18,000 at 1 hour — well above the 7,500 adequate-response threshold, showing the transfusion produced a strong platelet increment.

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Poor response suggesting refractoriness

Pre 15, post 18, BSA 1.8, 1 apheresis unit — 1 hour

Pre-transfusion platelet count 15 x10^3/µL Post-transfusion platelet count 18 x10^3/µL Body surface area 1.8 m^2 Platelets transfused 3.0 x10^11

The same-size apheresis unit only raised the count by 3 x10^3/µL. CCI = 3,000 x 1.8 / 3.0 = 1,800 at 1 hour — well below the 5,000 cutoff. One low value is not a diagnosis; if a second ABO-compatible, fresh-platelet transfusion also responds poorly with non-immune causes excluded, refractoriness workup (platelet antibody testing) is indicated.

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Estimating BSA from height and weight

Height 170 cm, weight 70 kg -> BSA 1.82 m^2

Height 170 cm Weight 70 kg

Mosteller BSA = sqrt(170 x 70 / 3600) ≈ 1.82 m². Using this BSA with a pre count of 20, post count of 50, and 1 apheresis unit (3.0x10^11) gives CCI = 30,000 x 1.82 / 3.0 ≈ 18,182 at 1 hour — an adequate response, matching the standalone BSA Calculator's result for the same inputs.

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Deep Dive

Understanding the Corrected Count Increment Calculator

3 chapters · 4 min read

After a platelet transfusion, the raw rise in platelet count depends heavily on the patient's size and how many platelets were transfused — so a bigger patient given a smaller dose can look like a 'poor responder' even with a completely normal transfusion response. The corrected count increment (CCI) standardizes the increment for both factors, making it the standard tool for judging whether a platelet transfusion worked and for screening for platelet refractoriness.

How the CCI formula works

CCI = [(post-transfusion platelet count − pre-transfusion platelet count) × body surface area] / platelets transfused. The platelet counts are entered in ×10³/µL, matching standard lab reporting, and are converted to an absolute cells-per-microliter increment before the formula is applied. Platelets transfused is expressed in ×10¹¹ — a standard single-donor apheresis unit contains roughly 3.0×10¹¹ platelets, while a pooled or random-donor unit contains roughly 0.55×10¹¹.

Dividing by the dose transfused and multiplying by BSA means the same absolute rise in platelet count produces a very different CCI depending on how large the patient is and how many platelets were given — which is exactly the point: it lets clinicians compare the quality of the response, not just the raw number.

Reading the result: adequate, borderline, or poor response

This calculator classifies the CCI against commonly cited cutoffs for each of the two conventional sampling windows. At 1 hour, a CCI of 7,500 or higher is generally considered an adequate response, and below 5,000 is considered a poor response; the range in between is borderline. At 18-24 hours (sometimes reported as 20 hours), the bar is lower — roughly 4,400 or higher is adequate and below 2,500 is poor — because some decline in the increment over a day is expected even in a good responder.

Exact cutoffs vary somewhat between sources (MDCalc, blood-bank reference tables, and the original clinical literature do not all use identical numbers), so treat these as commonly used reference points rather than a single universal law.

From a poor response to a refractoriness diagnosis

A single low CCI does not mean a patient is refractory. Platelet transfusion refractoriness is formally diagnosed only after at least two consecutive inadequate responses to ABO-compatible, fresh (less than 72 hours old) platelet units. The workup starts by ruling out the common non-immune causes of poor platelet survival — fever, sepsis, disseminated intravascular coagulation (DIC), splenomegaly, active bleeding, and graft-versus-host disease — since these are far more frequent than immune causes. If no non-immune cause explains the pattern, platelet antibody testing (HLA and platelet-specific) is used to confirm alloimmunization, which then guides whether HLA-matched or crossmatched platelets are needed for future transfusions.

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Questions

Frequently Asked Questions

6 questions

What is the formula for the corrected count increment (CCI)?+

CCI = [(post-transfusion platelet count − pre-transfusion platelet count) × body surface area (m²)] / (platelets transfused, ×10¹¹). Platelet counts are entered in ×10³/µL and converted internally to cells/µL before the increment is taken.

When should the post-transfusion platelet count be checked?+

Typically at two windows: 1 hour after the transfusion finishes, and again at 18-24 hours (sometimes reported as 20 hours). The 1-hour value assesses whether the transfusion produced an immediate increment; the 18-24 hour value assesses how well the increment held, which is more sensitive to non-immune consumption (fever, bleeding, splenomegaly).

What causes a low CCI?+

Non-immune causes include fever, sepsis, disseminated intravascular coagulation (DIC), splenomegaly, active bleeding, and graft-versus-host disease. Immune causes include HLA or platelet-specific alloimmunization from prior transfusions or pregnancy, which is confirmed with platelet antibody testing after non-immune causes are excluded.

What CCI counts as an adequate response?+

Commonly cited cutoffs are a CCI of at least 7,500 at 1 hour or at least 4,400 at 18-24 hours. Refractoriness is defined as two or more consecutive inadequate responses (commonly below 5,000 at 1 hour or below 2,500 at 18-24 hours) to ABO-compatible, fresh platelets, with non-immune causes ruled out. Exact cutoffs vary by source — see the Interpretation tab for the full reference table.

What units does this calculator use?+

Pre- and post-transfusion platelet counts are entered in ×10³/µL (e.g., 20 means 20,000/µL), BSA in m², and platelets transfused in ×10¹¹ — a typical apheresis unit contains about 3.0×10¹¹ platelets and a pooled/random-donor unit about 0.55×10¹¹.

What is the CCI used for?+

It standardizes the platelet increment for body size and dose transfused, so responses can be compared across patients and transfusions. It is the primary tool used in the workup of platelet transfusion refractoriness — distinguishing an inadequate response caused by non-immune consumption from one caused by alloimmunization.

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Platelet Counts & Dose