Quantra clot stiffness pattern: FCS, PCS, and CS
Quantra reports clot stiffness in three values — FCS, PCS, and CS. The goal is not to read each number in isolation, but to read them together as a pattern and ask which component is limiting clot strength.
Key points
- FCS reflects fibrin contribution to clot stiffness; it is not the same thing as plasma fibrinogen concentration.
- PCS reflects platelet contribution to clot stiffness; it is not the same thing as platelet count.
- CS, FCS, and PCS should be read as a pattern, then reassessed after targeted correction.
When to use this page
During perioperative or post-CPB bleeding, when a Quantra result is available and you are deciding what the CS, FCS, and PCS values mean together — before choosing a replacement strategy.
Why Quantra is useful
Quantra reports clot stiffness as three separate values: FCS, PCS, and CS. This separation matters because low clot strength is not a single diagnosis. The clinical question is not whether clot stiffness is low — it is which component is limiting clot strength, and whether a targeted correction is appropriate.
- Quantra can separate clot stiffness into fibrin contribution (FCS) and platelet contribution (PCS)
- This helps avoid treating low clot strength as one undifferentiated problem
- The goal is to identify whether fibrin contribution, platelet contribution, or both are limiting clot strength
What FCS means
FCS reflects the fibrin contribution to clot stiffness. When FCS is low, it may suggest inadequate fibrinogen contribution to clot strength. However, FCS should not be treated as a direct measurement of plasma fibrinogen concentration — the relationship is not one-to-one, and several factors affect how fibrinogen is reflected in FCS.
FCS is not plasma fibrinogen concentration
FCS reflects fibrin contribution to clot stiffness. Interpret it alongside the bleeding pattern, dilution, CPB timing, temperature, pH, calcium, and product exposure. Do not equate a low FCS value directly with a plasma fibrinogen level.
- Low FCS may suggest inadequate fibrinogen contribution — not a plasma fibrinogen concentration below a threshold
- Hemodilution, CPB, massive bleeding, and consumption can all reduce FCS
- Temperature, pH, calcium, and prior product administration all affect how fibrinogen performs in vivo
What PCS means
PCS reflects the platelet contribution to clot stiffness. When PCS is low, it may suggest inadequate platelet contribution — but this is not the same as a low platelet count. Platelet function is influenced by CPB, antiplatelet drugs, hypothermia, acidosis, and dilution, independent of the platelet count.
PCS is not platelet count
PCS reflects platelet contribution to clot stiffness, which depends on both platelet number and platelet function. A patient can have an acceptable platelet count with a low PCS if platelet function is impaired. Interpret PCS with the bleeding pattern, CPB status, antiplatelet exposure, and physiology.
- Low PCS may suggest inadequate platelet contribution — not simply a low platelet count
- CPB and antiplatelet drugs can impair platelet function even when the count appears acceptable
- Hypothermia, acidosis, and dilution further affect platelet behavior
What CS adds
CS reflects global clot stiffness — the combined result of fibrin and platelet contributions. A low CS alone does not tell you which component is limiting clot strength. That is what FCS and PCS help separate.
- Low CS can reflect low FCS, low PCS, or a mixed pattern
- Read CS alongside FCS and PCS to identify the dominant contributor
- A low CS with preserved FCS points toward the platelet contribution
- A low CS with low FCS and preserved PCS points toward the fibrin contribution
- Low FCS and low PCS together suggest a mixed pattern
CS alone does not guide treatment
A low CS is a signal that clot stiffness is reduced, not a product order. Reading FCS and PCS together tells you which component is contributing to the low CS — and which correction is most likely to help.
An action frame, not an automatic order
These values are pattern signals. They narrow the differential but do not replace clinical judgment, surgical field confirmation, or institutional protocol.
- Confirm clinically significant bleeding before treating a number in isolation
- Compare CS, FCS, and PCS together to identify the dominant pattern
- Check standard laboratory results and physiology — temperature, pH, ionized calcium, dilution
- Consider fibrinogen replacement, platelet therapy, or both only when supported by the pattern and institutional protocol
- Reassess clot stiffness and actual bleeding after treatment
- Re-check the surgical field if bleeding persists after correction
Take-home message
Quantra clot stiffness values are pattern signals, not product orders. FCS, PCS, and CS help separate fibrin contribution, platelet contribution, and mixed clot failure so treatment can be targeted and reassessed.
Clinical content by Kozo Watanabe, MD View profile →
Verify your decision
Low clot stiffness with significant bleeding → use the Quantra trigger guide to read FCS, PCS, and CS as a pattern, then reassess after targeted correction.
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