Thiazole orange: a complement to established methods for diagnosing inherited dense granule defects.

Area of Science:

• Hematology
• Flow Cytometry
• Platelet Physiology

Background:

• Inherited delta storage pool deficiencies are often underdiagnosed due to limited diagnostic tools.
• Accurate diagnosis of platelet dense granule disorders presents challenges for clinical laboratories.

Purpose of the Study:

• To evaluate thiazole orange (TO) as a flow cytometric marker for platelet dense granules.
• To compare TO with mepacrine for dense granule detection after protocol optimization.
• To assess TO's utility in differentiating quantitative granule defects from release defects.

Main Methods:

• Optimization of thiazole orange (TO) and mepacrine staining protocols for flow cytometry.
• Assessment of TO and mepacrine binding to dense granules in resting and activated platelets.
• Pilot study comparing TO staining with light aggregometry and CD63 expression in patients with suspected inherited platelet disorders.

Main Results:

• TO binds dense granules, showing a strong signal in resting platelets that decreases upon activation due to degranulation.
• Mepacrine showed a less pronounced signal decrease upon activation compared to TO.
• TO successfully differentiated quantitative dense granule defects from release defects, identifying abnormalities missed by other methods in a pilot study.

Conclusions:

• Thiazole orange (TO) is a promising diagnostic tool for identifying dense granule defects.
• TO can serve as a valuable complement to existing methods in the workup of inherited platelet disorders.
• TO's ability to track gradual dense granule release aids in distinguishing defect types.