An interventional study of Blood punction in Platelet Dysfunction, sponsored by University Hospital, Toulouse. Completed at 1 site in France. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2025-12-10.
Sponsored by University Hospital, Toulouse · Not applicable, Interventional, and Diagnostic
The primary purpose of the study is to evaluate a standardized method of screening for platelet signalling defects in patients with constitutional disorders of platelet function of unknown origin. We hypothesize that such defects are under-diagnosed in patients, due to heavy workup and requirement of relatively large blood sample by conventional biochemical methods. We propose to analyse kinase signalling downstream platelet membrane receptors using multiplex flow cytometry quantification and fluorescent platelet barcoding.
Little is known of the molecular basis of disorders of signalling pathways potentially responsible of constitutional defects of platelet functions (adhesion, aggregation or secretion) (1-5). Indeed, in routine practice, this investigation is limited by the complexity of the analyse using biochemical methods (western blotting), and the requirement of large amount of platelets.
We have designed a new approach for the quantification of platelet cytoplasmic phosphoproteins by flow cytometry. Fresh platelets in platelet rich plasma are analysed at baseline or after stimulation by major agonists (ADP, TRAP, thromboxane analogue, or collagen-related peptide), with and without relevant inhibitors of each pathway. Multiplex barcoding is used to identify each condition, allowing a high throughput analysis (6, 7). Platelet signalling profiling of Akt, Slp76, P38 MAPK and LIMK can be obtained from a blood sample of less than 10 ml, and within 6h The main objective of the study is to standardize the method between clinical laboratories with a standard expertise in flow cytometry. The study will be performed in 4 academic hospitals members of the French reference network of rare platelet diseases. Three groups of patients referred for mild or severe bleeding disorders will be included: 1) a control group of patients (30 per centre) with a bleeding disorder definitely other than of platelet origin (e.g. "low" von Willebrand); 2) a group of 10 patients per centre with definite constitutional platelet disorder (e.g. Glanzmann thrombasthenia) and 3) a group of 10 patients per centre with a defect of platelet function of unknown origin, potentially defective in signalling pathway.
The control group will serve to standardize the method between centres and to establish the reference values. A quality control will be set up by using frozen platelet preparations. The patients with definite platelet disorder will be useful for detecting potential signalling defects still not described in these pathologies. Platelet signalling defects which could be evidenced in these groups will be further identified by conventional biochemical and molecular methods after confirmation on a new sample.
If this new approach can be proposed to clinical laboratories working on rare platelet diseases, we expect an advance in our knowledge in the field. In addition the method has a potential in pharmaceutical innovation, for identifying (8) or monitoring new antiplatelet agents (9, 10), or identifying platelet defects induced by new "target therapies" designed for other diseases such as cancer or immune pathologies (10).
University Hospital, Toulouse is the lead sponsor of 794 studies on the registry; 214 are open to participants now.
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Exclusion Criteria:
Blood punction at patients with bleeding disorder definitely other than of platelet origin (e.g. "low" von Willebrand)
Other: Blood punction
Blood punction at patients with constitutional platelet disorder (e.g. Glanzmann thrombasthenia)
Other: Blood punction
Blood punction at patients with defect of platelet function of unknown origin, potentially defective in signalling pathway.
Other: Blood punction
T1 and T2: one blood punction with signalisation test (T1 for each arm, T2 at +6 months only if an anomaly at signalisation test is detected) signalisation test is made by flow cytometry Stage 1: for arm "bleeding disorder" : flow cytometry analysis to establish reference values observed in subjects without thrombopathy for each marker after agonist stimulation and corresponding search of an effect if a center-center effect is observed on the reference values its origin will be sought and corrected. Stage 2: for the two others arms: Several markers will be analyzed, corresponding to routes or levels of different signaling. For each of these markers, the test will evaluate quantitatively the phosphorylation activity of the protein tested.
standardise the method between clinical laboratories
This is a pilot study of a new approach of screening platelet signalling pathways disorders by flow cytometry with methodological primary outcomes (12) as follows: 1)to standardise the method between clinical laboratories, 2)to establish reference values of the method and 3)to design a quality control assessment The primary endpoint will focus on the overall variability of reference values observed in subjects without thrombopathy for each marker after agonist stimulation and corresponding search of an effect if a center-center effect is observed on the reference values its origin will be sought (deviation from the protocol, reagent lot .....) and corrected. The "center effect" will also be analyzed by the quarterly quality control, which will compare the results obtained from the same wafer tests analyzed simultaneously in three sites.
Time frame: 3 years
To describe the signalling pathways in platelet disorders
To describe the signalling pathways in platelet disorders with definite diagnosis To screen putative defects in bleeding patients with disorders of platelet function of unknown origin To identify more deeply the defects found in these groups. Several markers will be analyzed, corresponding to routes or levels of different signaling. For each of these markers, the test will evaluate quantitatively the phosphorylation activity of the protein tested. We can thus determine for each subject and each marker, the response to the test defined by: * The percentage increase in the signal (relative to the rest) after stimulation with a receptor agonist, * The percentage increase in the signal (relative to the rest) in the presence of the agonist to the associated receptor antagonist.
Time frame: 3 years
This study is completed, as verified in Apr 2019. You cannot join it, but the record below documents what was studied.
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University Hospital, Toulouse