Reference Range of Platelet Delta Granules in the Pediatric Age Group: An Ultrastructural Study of Platelet Whole Mount Preparations from Healthy Volunteers

Abstract

This study sought to determine delta granule normal ranges for children and to validate methodology for the appropriate diagnosis of delta granule deficiency (storage pool disease) by using the whole-mount technique in electron microscopy. Specimens obtained from 40 healthy volunteers (2 months of age through 21 years old, 21 females and 19 males) were tested. Results showed dense granules/platelet (DG/Plt) ranged from 1.78 to 5.25. The 5th percentile was 1.96 DG/Plt with an overall mean ± SEM 3.07 ± 0.12 DG/Plt. In comparison, a previously published lower cutoff value, 3.68 DG/Plt, was significantly higher than the mean from our volunteers (P < 0.0001). We found no variability in dense granules/platelet based on race or sex and no significant variation by age subgroup. Pending wider studies, the value of 2 DG/Plt is a more appropriate lower limit of normal. In the absence of wider studies (in healthy volunteers and patients), laboratories should consider establishing their own reference ranges.

Weak correlation of bleeding scores to platelet electron microscopy: A retrospective chart review of pediatric patients with delta‐storage pool disorder

“…Using PEM alone to establish the diagnosis has recently become controversial, and the average granules per platelet in our cohort is near the observed average in healthy pediatric patients . Sorokin et al concluded a new diagnostic threshold of 2 dg/pl would in fact be more specific, but guaranteed to be less sensitive, proven by our study population as this value would have diagnosed merely 31% of our study population.…”

“…Therefore, PEM results are difficult to interpret irrespective of the use of a more theoretically specific cutoff such as <2 dg/pl or the more sensitive cutoff of <3.68 dg/pl. In our population, PEM did not show any correlation to the patient's age, which has yet to be observed in the pediatric population . Given a lack of consensus regarding the reference range for PEM in pediatric patients, clinical research consideration should be given to flow cytometry in either establishing or confirming a δ‐SPD diagnosis since our current strategies inadequately classify patients .…”

“…The traditional, whole‐mount technique of electron microscopy evaluates the dense granule contents of 100 to 300 platelets to determine the mean dense granule per platelet (dg/pl) value . A diagnostic threshold of <2 dg/pl has been proposed in the pediatric population, making the test character more specific, yet a consensus has yet to be agreed upon in children . Although the utilization of flow cytometry is not widely accepted or used in routine clinical practice for δ‐SPD, CD‐63 has been proposed and utilized in determining the severity of dense granule deficiency …”

Utility of a screening tool for haemostatic defects in a multicentre cohort of adolescents with heavy menstrual bleeding

“…Qualitative platelet dysfunction was diagnosed when there was impaired aggregation to one or more agonists (except isolated epinephrine defects) or impaired ATP secretion with reproducible findings on ≥2 occasions . A cut‐off of 2 or fewer dense granules/platelets was used as a diagnostic cut‐off to diagnose platelet storage pool disorders . Clotting factor deficiency was defined when a clotting factor level was below the age‐based reference range.…”

“…19 A cut-off of 2 or fewer dense granules/platelets was used as a diagnostic cut-off to diagnose platelet storage pool disorders. 20 Clotting factor deficiency was defined when a clotting factor level was below the agebased reference range. Thrombocytopenia was defined as platelet count <150/cumm.…”