Test Catalog

Test ID: PTEM    
Platelet Transmission Electron Microscopic Study, Whole Blood

Useful For Suggests clinical disorders or settings where the test may be helpful

Diagnosing platelet disorders

Genetics Test Information Provides information that may help with selection of the correct genetic test or proper submission of the test request

This test is indicated for assessing platelet ultra-structural abnormalities in congenital and acquired platelet disorders.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Patients with either hereditary or acquired platelet disorders usually have bleeding diathesis, which can potentially be life threatening. A reliable laboratory diagnosis of a platelet disorder can significantly impact patients' and, potentially, their family members' clinical management and outcome.


Platelet (P) transmission electron microscopy (TEM) has been an essential tool for laboratory diagnosis of various hereditary platelet disorders since it was first used to visualize fibrin-platelet clot formation in 1955. PTEM employs 2 main methods to visualize platelet ultrastructure, whole mount (WM) TEM and thin section (TS) TEM.


WM-TEM is considered the gold standard test for diagnosing dense granule deficiencies in Hermansky-Pudlak syndrome, alpha-delta platelet storage pool deficiency, Paris-Trousseus-Jacobsen syndrome, Wiskott-Aldrich syndrome, TAR (thrombocytopenia, absent radii) syndrome, Chediak-Higashi syndrome, and more.


TS-TEM is a preferred method to visualize platelet alpha granules, other organelles and abnormal inclusions.


Platelet disorders that can be detected by PTEM include (but are not limited to):


Delta granules (dense bodies):

-Hermansky Pudlak syndrome

-Wiskott-Aldrich syndrome

-Chediak Higashi syndrome

-Jacobson/Paris Trousseau syndrome

-York platelet syndrome

-Storage pool deficiency, not otherwise specified


Alpha granules:

-Gray platelet syndrome

-White platelet syndrome

-X-linked GATA 1 mutation

-Jacobson/Paris Trousseau syndrome


Alpha and delta granules:

-Alpha-delta storage pool deficiency

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Mean dense granules/platelet > or =1.2

Interpretation Provides information to assist in interpretation of the test results

Ultrastructural abnormalities identified by platelet transmission electron microscopy (TEM) are evaluated by a Mayo hematopathologist.


Platelet size, alpha granules, golgi complex, and abnormal inclusions will be assessed as part of the morphologic examination under TEM.


Distinct and sometimes pathognomonic ultrastructural abnormalities are found in Hermansky Pudlak syndrome, gray platelet syndrome with virtually absent alpha granules, white platelet syndrome, Medich giant platelet disorder, X-linked GATA-1 macrothrombocytopenia, and, recently described, York platelet syndrome.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Whole blood sample collected in an ACD tube should be stored and transported at ambient temperature within 72 hours of collection. Suboptimal transportation may cause falsely low dense granule counts.

Supportive Data

Extensive validation studies with normal donors and known patient samples were performed. A total 111 normal donor platelet samples were assessed to establish the baseline. Of the 10 patient samples, 6 were from patients with Hermansky-Pudlak syndrome, 2 patients had gray platelet syndrome, 1 had MYH9 mutation-associated platelet disorder, and 1 had Paris-Trousseau/Jacobson syndrome.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. White JG: Electron-dense chains and clusters in platelets from patients with storage pool-deficiency disorders. J Thromb Haemost. 2003 Jan;1(1):74-79

2. White JG: Use of the electron microscope for diagnosis of platelet disorders. Semin Thromb Hemost. 1998;24(2):163-168

3. Chen D, Uhl CB, Bryant SC, et al: Diagnostic laboratory standardization and validation of platelet transmission electron microscopy. Platelets. 2018 Sep;29(6):574-582 doi: 10.1080/09537104.2018.1476682

Special Instructions Library of PDFs including pertinent information and forms related to the test