Point-of-Care Testing in Patients with Hereditary Disorders of Primary Hemostasis: A Narrative Review

Inherited disorders of primary hemostasis, such as von Willebrand disease and congenital platelet disorders, can cause extensive, typically mucocutaneous bleeding. Assays to diagnose and monitor these disorders, such as von Willebrand factor activity assays and light transmission aggregometry, are performed in specialized hemostasis laboratories but are commonly not available in local hospitals. Due to the complexity and relative scarcity of these conventional assays, point-of-care tests (POCT) might be an attractive alternative in patients with hereditary bleeding disorders. POCTs, such as thromboelastography, are increasingly used to assess hemostasis in patients with acquired hemostatic defects, aiding clinical decision-making in critical situations, such as during surgery or childbirth. In comparison, the use of these assays in patients with hereditary hemostasis defects remains relatively unexplored. This review aims to give an overview of point-of-care hemostasis tests in patients with hereditary disorders of primary hemostasis. A summary of the literature reporting on the performance of currently available and experimental POCTs in these disorders is given, and the potential utility of the assays in various use scenarios is discussed. Altogether, the studies included in this review reveal that several POCTs are capable of identifying and monitoring severe defects in the primary hemostasis, while a POCT that can reliably detect milder defects of primary hemostasis is currently lacking. A better understanding of the strengths and limitations of POCTs in assessing hereditary defects of primary hemostasis is needed, after which these tests may become available for clinical practice, potentially targeting a large group of patients with milder defects of primary hemostasis.

[Clinical observation of desmopressin in the treatment of 15 patients with DDAVP]

Objective: To assess the significance of DDAVP use in the diagnosis and treatment of VWD. Methods: An analysis of 15 VWD cases who referred to Hematology Division of First affiliated Hospital of Soochow University and treated with DDAVP from March 2016 to August 2018 was conducted. Efficacy and treatment response of DDAVP were monitored by observations of changes in factor Ⅷ procoagulant (FⅧ∶C) and von Willebrand Factor (VWF) related indicators before and 2 h after DDAVP injection. Results: Of 15 cases with VWD, 7 males and 8 females with a median age of 23 (6-46) years, 7 of 9 type I VWD patients achieved complete response (CR) , 1 type 2A VWD case CR, 5 type 3 VWD ones no response (NR) . The VWF multimer analysis in 5 patients combined with other plasma VWF values were in accordance with the known diagnosis. Conclusions: DDAVP was effective in most type 1 patients, and ineffective in some type 2 and almost all type 3 cases. It was helpful for diagnosis and subsequent treatment planning.

Evaluation of a modified thromboelastography assay for the screening of von Willebrand disease

Thromboelastography (TEG) has been shown to be a valuable point-of-care device for the rapid diagnosis of various bleeding disorders. However, TEG has thus far not been used for the screening for von Willebrand disease (VWD). We evaluated the performance of a modified TEG assay for the laboratory screening of VWD. Three hundred twenty-eight patients (148 male, 180 female, median age 8.4 years, range 0.1 – 72.7 years) were included in the study. The diagnosis and classification of patients was based on personal and familial case history, von Willebrand factor antigen, ristocetin cofactor levels, collagen binding assay, factor VIII coagulant activity and multimer analysis. The ratio of clot strength after preincubation with ristocetin, and without ristocetin, represents the component of clot strength that is formed by cross-linked fibrin fibres and is dependent on the agglutinated platelet fraction. The decrease of the maximum amplitude is a function of the ristocetin concentration and provides a diagnostic parameter able to differentiate between healthy individuals and patients having VWD. Based on a preliminary cut-off value of 25% for the area under the curve (AUC) ratio, the sensitivity varied from 53% to 100% for the different VWD patient groups. The test is suitable for use as a screening test using whole blood and has the additional benefit of being suitable as a point of care test. It appears also useful for monitoring responses to desmopressin (DDAVP) and infusion therapy.

The use of DDAVP in children with bleeding disorders

Desmopressin (1-deamino-8-D-arginine vasopressin, DDAVP) has been used in children with von Willebrand disease (VWD) and Hemophilia A for almost 35 years. This treatment has substantially lowered the number of children exposed to human plasma derived products, with a good safety profile, and at very low cost. The response to DDAVP has been shown to be associated with age, baseline factor level, and genetic mutations. A DDAVP challenge test is recommended. DDAVP has also been used to prevent and treat bleeding episodes in children with platelet function defects and other disorders associated with bleeding tendency.

Response to low-dose desmopressin by a subcutaneous route in children with type 1 von Willebrand disease

OBJECTIVE

The primary objective of this study was to determine responses to low-dose desmopressin (DDAVP) by a subcutaneous route in children with type 1 VWD.

METHODS

This study analyzed responses to low doses of DDAVP administered by a subcutaneous route to 14 children between the ages of 3 and 16 with type 1 VWD and a personal and familial history of bleeding. At 0 (baseline) and 1 hour (initial response) after the subcutaneous injection of DDAVP, the vital signs were assessed and blood samples were obtained for VWD panel determinations (VWF:Ag, VWF:RCo, FVIII:C levels, and Col/Epi, Col/ADP). At 4 hours (sustained response), only Col/Epi and Col/ADP were assessed.

RESULTS

The DDAVP mean (min-max range, μg/kg) based on the patient's weight was 0.15 (0.12-0.18). Laboratory values mean (min-max range in U/dl) baseline for VWF:RCo, VWF:Ag, and FVIII:C were 28 (20-36), 34 (25-42), and 40 (29-48), respectively. After a subcutaneous administration, the laboratory values mean (min-max range in U/dl(-1)) achieved for 1 hour for VWF:RCo, VWF:Ag, and FVIII:C were 109 (72-144), 132 (88-166), and 151 (96-198), respectively. PFA 100(®) CT (Col/Epi <134 seconds and Col/ADP <110 seconds) returned to normal values at 1 and 4 hours after a subcutaneous administration.

CONCLUSION

Subcutaneous low-dose DDAVP therapy is at least effective as 0.3 µg/kg intravenous therapy for children with type 1 VWD. This study shows that a wider use of DDAVP should be promoted, especially in developing countries.