Background: PTEM whole mount (WM) is a standard method for evaluating platelet dense granules (pDG). However, a pediatric/adolescent pDG reference range (RR) and prevalence of pDG deficiency in symptomatic patients has not been well-established.

Aims: This study aimed to establish a pediatric/adolescent RR for mean pDG and determine the prevalence of pDG deficiency in a cohort of patients who had clinical suspicion for platelet disorders (PD).

Methods: First, WM-PTEM was performed on healthy donors. A mean pDG RR was calculated by averaging DG of 100 plt per patient as previously described (PMID: 29863946). Next, patients undergoing laboratory evaluation of suspected PD were recruited to this study. In addition to routine laboratory testing, their ISTH BAT score (normal <3; abnormal >3) was correlated with mean pDG.  

Results: Healthy donors (n=77, 41.6% female), ages 3-18 years, had a mean pDG 2.7 (+/- 0.5) ranging from 1.9 to 3.8. The mean pDG did not correlate with age or gender. The tentative RR was calculated to be 1.9 to 3.8 DG/platelet. Nineteen patients over the age of three (25.3%, n=19/75)  had <1.9 mean pDG. Of the 75 symptomatic patients (age 3-18 years, 69.3% female), 42 and 33 patients had BAT scores >3 and <3 (range 0-11), respectively. DG/plt in pt with bleeding scores >3 (mean=2.3 +/- 0.83, n = 42) vs. those with bleeding scores < 3 (mean=2.3+/-0.66, n = 32) (p=.206) were similar. There was no difference in the number of patients with normal or abnormal bleeding scores in groups with normal vs decreased mean DG/plt (p=.595).

Conclusions: In this study, we established a tentative pediatric RR for platelet DG at 1.9 – 3.8 DG/plt. Approximately 25% of patients were found to have DG deficiency. However, pDG did not not correlate with the ISTH BAT.  

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/evaluation-of-platelet-dense-granules-by-transmission-electron-microscopy-ptem-in-pediatric-patients-and-healthy-pediatric-donors/