Does Thrombocyte Size Give Us an Idea about Thrombocytosis Etiology?

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1. Introduction

The average platelet (PLT) count in most clinical laboratories ranges from 150 × 10⁹/L to 350 × 10⁹/L or 450 × 10⁹/L, although the level for any individual is maintained within small limits from day to day [1]. The three most important physiopathologic reasons of thrombocytosis are clonal, including essential thrombocythemia (ET) and other chronic myeloproliferative disorders, familial, including hereditary cases of nonclonal myeloproliferation resulting from thrombopoietin and thrombopoietin receptor mutations, and reactive, where thrombocytosis occurs secondary to various acute and chronic clinical conditions [2]. ET has traditionally been a diagnosis of exclusion, requiring the absence of reactive conditions and other clonal disorders that may present with thrombocytosis [3]. In the presence of a pathogenetic mutation in JAK2 V617F or MPL, a differential diagnosis of ET from reactive causes is relatively simple. However, in patients with suspected ET who lack JAK2 V617F and MPL mutations, the exclusion of secondary causes is especially important.

The study was designed to evaluate the clinical application of mean platelet volume (MPV), hemoglobin (Hb), red blood cell indices, white blood cell (WBC), serum iron profile, and C-reactive protein (CRP) level in the differential diagnosis of thrombocytosis.

2. Materials and Methods

2.1. Patients

The medical records of 49 patients, diagnosed to have reactive thrombocytosis (RT) (group 1, $n=26$ ) and ET (group 2, $n=23$ ) between 2008 and 2009, were retrospectively reviewed (Table 1). The diagnosis of ET was made according to the 2008 World Health Organization (WHO) diagnostic criteria [4]. Reactive thrombocytosis was defined as a PLT count > 450 × 10⁹/L; we have included only cases of iron deficiency anemia (IDA). The diagnosis of IDA was based on Hb concentration less than 13.5 g/dL in male, less than 12 g/dL in female, mean corpuscular volume (MCV) less than 80 fL, ferritin concentration less than 15 mcg/L in male and less than 5 mcg/L in female [5]. Patients with acute blood loss and those requiring parenteral iron replacement therapy, chronic renal failure, hypertension, coronary vascular disease, diabetes mellitus, cigarette addiction,...