An interventional study of Research samples blood viscosity and viscoelasticity: in Polycythemia and Polycythemia Vera (PV), sponsored by Hospices Civils de Lyon. Not yet recruiting at 1 site in France. Open to participants aged 18 Years to 70 Years. Per ClinicalTrials.gov, last updated 2026-01-15.
Sponsored by Hospices Civils de Lyon · Not applicable, Interventional, and Basic science
Polycythemia vera (PV) is a rare haematological disorder characterized by an excessive production of red blood cells, associated with the somatic JAK2 V617F mutation. Clinical manifestations are varied and often include exercise intolerance but the underlying mechanisms remain poorly understood.
Physical activity is recommended in the management of chronic diseases, but it must be tailored to the physiological profile of the patient. A cardiopulmonary exercise test (CPET) is essential to ensure safety, detect possible contraindications, and assess maximal oxygen uptake (VO₂max), a key indicator of aerobic performance.
This prospective, experimental, non-randomized study will include patients with PV followed at Lyon Sud University Hospital and for which a CPET is scheduled in their routine clinical follow-up. The primary objective is to compare VO₂max between two groups of patients: moderate (\<10%) versus marked (≥10%) extent of blood viscosity increase after the completion of the CPET. The main hypothesis is that a significant increase in blood viscosity during exercise (≥10%) is a major limiting factor in oxygen transport and leads to a reduced VO₂max, reflecting impaired exercise tolerance.
Secondary analyses will focus on hemorheological parameters, tissue oxygenation, and cardiorespiratory and metabolic responses. The study aims to better understand the biological and physiological determinants of exercise intolerance in this population.
32 studies on the registry are indexed under Polycythemia; 12 are open to participants now.
This study's planned enrollment of 54 is below the median of 67 across 22 interventional studies indexed under Polycythemia.
Browse Polycythemia studies →Hospices Civils de Lyon is the lead sponsor of 1,866 studies on the registry; 448 are open to participants now.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Patients diagnosed with polycythemia vera, with confirmed presence of the JAK2 V617F mutation, who wish to resume regular daily physical activity and have been prescribed an exercise test for this purpose as part of their follow-up at Lyon Sud Hospital
Biological: Research samples blood viscosity and viscoelasticity:
Research samples: Blood rheology: hematocrit, blood viscosity, deformability and erythrocyte aggregation, viscoelasticity
Also known as: the level of tissue oxygenation and hemoglobin oxygenation that will be measured by near-infrared spectroscopy (NIRS).
Blood viscosity (Centipoise) at 6 shear rates.
Blood viscosity will be measured using a cone-plate viscometer (Brookfield, model LVDVII+ PRO, cone CPE 40) on native hematocrit blood, at 7 different shear rates: 2.25, 4.5, 11.5, 22.5, 45, 90, and 225 s-¹, using an ascending ramp shear protocol.
Time frame: Measurements will be performed at baseline (pre-test), at 3 minutes post-CPET, and at 60 minutes post-CPET
Rheological properties of blood: deformability and aggregation of erythrocytes
Analyses will be performed on EDTA tubes. Erythrocyte deformability will be measured by ektacytometry at 9 shear stresses (0.3-30 Pa) under isotonic conditions. Maximal elongation index (EImax) and shear stress for 50% deformation (SS₁/₂) will be recorded. Aggregation/disaggregation will be assessed by syllectometry at 40% hematocrit. Parameters include aggregation index (AI) and minimal shear rate (γmin) for full disaggregation
Time frame: Measurements will be performed at baseline (pre-test), at 3 minutes post-CPET, and at 60 minutes post-CPET.
Viscoelasticity of blood
Viscoelastic properties of blood will be assessed using rotational thromboelastometry (ROTEM delta) on citrated blood tubes. The following tests will be performed: NATEM, TEMACT, FIBTEM, and EXTEM. For each test, the following parameters will be measured: clotting time (CT, in seconds), clot amplitude at 5, 10, 20, and 30 minutes (A5, A10, A20, A30, in mm), alpha angle (indicating clot formation velocity, in degrees), maximum clot firmness (in mm), percentage of clot lysis at 30 minutes (LI30), as well as lysis onset time (LOT) and total lysis time (LT), both expressed in seconds
Time frame: Measurements will be performed at baseline (pre-test), at 3 minutes post-CPET, and at 60 minutes post-CPET
Tissue and haemoglobin oxygenation with near-infrared spectroscopy (NIRS)
Near-infrared spectroscopy (NIRS) will be performed using the Portamon MKIII system (Artinis) with a sampling rate of 100 Hz. This non-invasive technique involves placing surface electrodes on the skin over the vastus lateralis muscle, halfway between the anterior superior iliac spine and the patella. NIRS enables continuous monitoring of changes in oxyhemoglobin (HbO₂) and deoxyhemoglobin (HHb) concentrations, allowing for the calculation of the tissue oxygenation index (TOI)
Time frame: Measurement will be performed during the CPET.
Plan to share: No
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