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during widespread intravascular coagulation. This depletion contributes to hypocoagulability and bleeding risk, with fibrinolysis variably contributing, depending on the stage of the sepsis.21 In suspected DIC, the plasma-to-
serum viscosity (PV:SV) ratio will reflect the consumption of cloting proteins, particularly fibrinogen. A changing PV:SV ratio will indicate evolving coagulopathy and support early recognition of DIC with standard laboratory tests.
Understanding PV:SV Plasma and serum viscosity ratio refers to the relationship between the viscosity of plasma and that of serum from the same patient.22
Category Formula
Measurement conditions Units
Normal Normal
Calculation Final reference
Parameter PV:SV ratio Temperature Viscosity units
Plasma viscosity Serum viscosity PV:SV ratio
Normal PV:SV ratio Normal plasma : serum viscosity ratio. Stage The normal PV is slightly
higher than SV. This reflects the fact that plasma contains fibrinogen and other clotting factors, while serum does not. Therefore, serum viscosity is primarily influenced by the concentration and size of circulating proteins, particularly immunoglobulins and paraproteins, in a patient sample. The PV:SV ratio indicates which protein components are elevated and contribute to abnormal viscosity in a patient sample. Early sepsis is characterised by a
marked increase in plasma viscosity, largely atributable to elevated acute- phase reactants such as fibrinogen and other plasma proteins produced during the systemic inflammatory response to infection.23
In contrast, serum viscosity
may remain within normal limits or show only a modest increase in earlier stages. In more advanced or severe cases, both plasma and serum viscosity become elevated, indicating a wider
of sepsis Early
(hyperinflammatory) Established sepsis
Late / septic shock Plasma Serum ↑ PV:SV
viscosity viscosity ratio ↑↑↑
High ↑↑ ↑↑ ↓ / → ↑ Moderate Rationale
Surge in fibrinogen and acute-phase proteins (plasma viscosity rises more)
Persistent inflammation rises both fibrinogen and immunoglobulins, increasing plasma and serum viscosity
Low-Normal Fibrinogen consumption, possible DIC Illustration of plasma : serum viscosity ratio across stages of sepsis.
rise in circulating proteins, including immunoglobulins, driven by immune activation and dysregulated inflammation. This hyperviscosity state will impair microcirculatory flow and will contribute to organ dysfunction.
Phase-dependent dynamics of the PV:SV ratio The PV:SV ratio exhibits a dynamic, phase-dependent pattern during the progression of sepsis, reflecting
underlying changes in coagulation and inflammatory protein composition. Serial monitoring of the PV:SV ratio
will provide a real-time biomarker indicator of the evolving balance between inflammatory and consumptive processes. When, interpreted with other clinical markers, this ratio has the potential to help identify critical transition points and guide phase-specific therapeutic interventions.
Details/Values/Calculation PV / SV
Measured at 37°C, reported at 25°C
mPa.s or cP, numerically equivalent and interchangeable
1.60 mPa.s (mean PV value) 1.50 mPa.s (mean SV value) 1.60 / 1.50 = 1.06 1.06
June 2026
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