Platelet size distinguishes between inherited macrothrombocytopenias and immune thrombocytopenia

Abstract

Summary. Background: Distinguishing inherited thrombocytopenias from immune thrombocytopenia (ITP) can be difficult, and patients are therefore at risk of misdiagnosis and inappropriate treatments. Although it is known that the most common inherited forms of thrombocytopenia are characterized by increased platelet size, the diagnostic power of this feature has never been investigated. Objectives: The aim of this study was to test the hypothesis that platelet size can be used to differentiate ITP from inherited macrothrombocytopenias. Patients/ methods: We measured mean platelet volume (MPV) and mean platelet diameter (MPD), within 2 h of blood sampling, in 35 patients with inherited macrothrombocytopenias [15 MYH9-related disease (MYH9-RD), three biallelic and 17 monoallelic Bernard-Soulier syndrome (BSS)], and 56 with ITP. Using receiving operating characteristic analysis, we searched for the best cut-off values to differentiate between these conditions. Results: As expected, platelets were larger in inherited macrothrombocytopenias than in ITP. An MPD larger than 3.3 lm differentiated MYH9-RD and BSS from ITP with 0.89 sensitivity and 0.88 specificity, and an MPV larger than 12.4 fL had 0.83 sensitivity and 0.89 specificity. Combining MPD with MPV increased sensitivity and specificity to 0.97 and 0.89, respectively. Conclusion: Platelet size evaluation by both an appropriate cell counter and blood film examination is useful for differentiating inherited macrothrombocytopenias from ITP.

Macrothrombocytopenia in North India: Role of Automated Platelet Data in the Detection of an Under Diagnosed Entity

“…They reported that platelets were larger in inherited macrothrombocytopenias than in ITP. Combining MPD with MPV increased sensitivity and specificity of macrothrombocytopenia diagnosis to 0.97 and 0.89, respectively [17]. In our study too, the MPV in patients with macrothrombocytopenia was significantly higher (p \ 0.00001) than that seen in patients with ITP and secondary thrombocytopenia.…”

Platelet diameters in inherited thrombocytopenias: analysis of 376 patients with all known disorders

“…The first study found that an MPD larger than 3.3 mm differentiated MYH9-RT, mBSS, and bBSS from ITP with 89% sensitivity and 88% specificity. 7 The second study, evaluating a different patient population, found that the same cutoff value had 67% specificity and 75% sensitivity in differentiating these conditions from ITP. 5 This study confirmed that MPD has good diagnostic accuracy in distinguishing ITs with giant platelets (hMYH9-RD, tMYH9-RD, and bBSS) not only from ITP but also from all other ITs.…”

“…On average, 200 platelets were evaluated in each patient, and the maximum diameter of each platelet was recorded. 7 Platelets in clumps or those with extending pseudopodia were not considered. Technicians who measured the diameters were blinded to the patients' diagnoses.…”

“…6 As a consequence, what we presently know about this subject is derived mainly from case reports, series of patients with one form of IT, and two small studies that directly compared platelet size in some of the known ITs. 5,7 To advance knowledge in this field (taking into account the present limitations of cell counters), we performed a collaborative study to measure platelet size by image analysis of peripheral blood smears obtained from patients affected by all 19 forms of IT currently known.…”

Eltrombopag for the treatment of the inherited thrombocytopenia deriving from MYH9 mutations

“…Since electronic counters greatly underestimate both platelet count and volume in subjects with MYH9-RD, 18 platelet counts were also evaluated by phase-contrast microscopy in a counting chamber, and platelet size was measured by software-assisted microscopy examination of peripheral blood films. 19 Only platelet counts measured by microscopy were used for the purposes of this study.…”