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Platelet function tests in childhood. Measuring aggregation and release reaction in whole blood
R Knöfler1, G Weissbach, E Kuhlisch
1Department of Pediatrics, Medical Faculty of Technical University, Dresden, Germany.
Insights
Newborns exhibit diminished primary hemostasis, particularly collagen-induced responses, which normalize by childhood. Whole blood assays reveal age-related differences in platelet function and bleeding time, influenced by hematocrit and leukocyte counts.
Area of Science:
- Hematology
- Pediatric Medicine
- Hemostasis Research
Background:
- Primary hemostasis evaluation is crucial for assessing bleeding risk.
- Age-specific reference ranges for hemostatic parameters are not fully established.
- Whole blood assays offer a comprehensive assessment of platelet function.
Purpose of the Study:
- To investigate age-related differences in primary hemostasis parameters.
- To evaluate the influence of blood cell counts on hemostatic function.
- To compare hemostatic function in newborns, children, and adults using whole blood techniques.
Main Methods:
- Whole blood samples from newborns, infants/schoolchildren, and adults were analyzed.
- Agonist-induced platelet aggregation and adenosine triphosphate (ATP) release were measured.
- In vitro bleeding time was assessed using the PFA 100 system.
Main Results:
- Newborns showed diminished aggregation and adenosine triphosphate (ATP) release with collagen, correlated with lower hematocrit and leukocyte counts.
- Platelet count influenced many aggregation phenomena.
- PFA 100 closure time and blood flow velocity were inversely correlated with hematocrit and leukocyte count, notably reduced in newborns.
- Responses to adenosine diphosphate (ADP), arachidonic acid, and ristocetin were similar across age groups.
- Hemostasis parameters normalized during childhood, showing no significant differences from adults.
Conclusions:
- Newborns exhibit transient hypofunction in primary hemostasis, particularly concerning collagen-induced platelet activation.
- Hematocrit and leukocyte counts significantly influence in vitro bleeding time and platelet aggregation.
- Age-specific reference values are essential for accurate interpretation of hemostasis tests in pediatric populations.
Abstract:
Blood samples from 42 newborns, 78 infants and schoolchildren, and 81 healthy adults were tested for the parameters of primary hemostasis. Only whole blood techniques were used. Agonist-induced aggregation and release-reaction studies were performed in a whole blood lumi-aggregometer simultaneously. The release of adenosine triphosphate (ATP) was detected by the luciferin-luciferase method. The in vitro bleeding time was measured by the PFA 100 system. The results of these studies were ostensibly influenced by blood cells. Many aggregation phenomena were correlated with the platelet count. Aggregation and release reaction by collagen were inversely correlated with the hematocrit. In the PFA 100, hematocrit and leukocyte count were also inversely correlated with the closure time and the maximal blood flow velocity. Both parameters were diminished in newborns. The aggregation response to adenosine diphosphate (ADP) was similar in the three groups. The same was true for the aggregation and release reaction by arachidonic acid and for the agglutination by ristocetin. The aggregation and release reaction by collagen were diminished in the specimens from newborns. For the explanation of this transient hypofunction, only theoretical considerations exist. Beyond the postnatal period and during childhood, no remarkable differences from the adult norm were found.
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