Cytometry, Immunofluorescence Microscopy, and Light Transmission Aggregometry in the Diagnosis of Platelet Functional Disorders

Background: The diagnosis of platelet function is often difficult and the required laboratory tests can only be performed in specialized centers. Light transmission aggregometry (LTA) is the gold standard method to evaluate platelet function, but it requires a large volume of blood. On the other hand, immunofluorescence microscopy (IFM) and flow cytometry (FC) can be performed with a very small amount of blood. We present here the application of these three methods in the diagnosis of two cases with platelet dysfunction.

Case 1: A 33-year-old male patient presented with increased bleeding tendency. Plasmatic components of the coagulation were normal. LTA showed decreased aggregation response with epinephrine (low/high), ADP (low/high), and collagen (low). ATP release with ionophore was also reduced. IFM showed reduced Lamp 2 and CD63 in platelets. FC revealed reduced CD63 expression upon activation with TRAP-6. These findings are consistent with delta-storage pool disease.

Case 2: A 62-year-old female patient presented with an increased bleeding tendency. Coagulation factors and von Willebrand factor were normal. LTA showed decreased aggregation response with epinephrine (low/high), ADP (low), collagen (high), and TRAP (low/high). ATP release with ionophore was also reduced. IFM showed decreased expression of Lamp 1 and CD63 in platelets. Decreased expression of CD63 and CD62p was detected in FC. These findings are consistent with storage pool disease.

Conclusion: LTA remains the gold standard, but IMF and FC are increasingly used in the diagnosis of platelet function disorders. Both methods require a small amount of blood, which is especially advantageous in children. However, standardization of FC protocols for the evaluation of platelet function is needed.

Publication History

Article published online:
26 October 2022