AIMS: JAK2V617F (JAK2), calreticulin (CALR) and MPL515L/K (MPL) mutations are 
important in essential thrombocythemia (ET) and may be associated with various 
clinical consequences of the disease. This study aimed to compare the clinical 
and haematological parameters of ET patients regarding the mentioned mutations 
and the role of plateletcrit (PCT).
METHODS: Seventy patients who were diagnosed with ET between 2005 and 2017 in a 
single centre were included in this descriptive study. The initial symptoms and 
clinical findings were retrieved from the electronic database. JAK2 gene V617F 
mutations, MPL gene exon 10 mutations and CALR gene exon 9 DNA sequence analyses 
were performed. Forty-one healthy volunteers were included to perform ROC curve 
analysis for interpreting PCT value.
RESULTS: The distributions of patients according to the mutations were as 
follows: Thirty-seven (52.9%) patients were JAK2-positive, 15 (21.4%) were 
CALR-positive, 2 (2.8%) patients were positive for both CALR and JAK2, and 1 
(1.4%) was only MPL-positive. Fifteen (21.4%) patients were triple-negative. The 
ET patients with JAK2 mutation showed a higher level of haemoglobin at the time 
of diagnosis. The ET patients with CALR mutation presented with higher platelet 
and LDH levels (P = .002 and P = .001, respectively). The PCT level was higher 
in the CALR-positive group when compared to the others (P = .026). A sensitivity 
value of 97.6% and specificity value of 98.6% were determined regarding PCT% at 
a cut-off value of 0.37 in ET patients. In CALR-positive patients, the 
sensitivity and specificity values were 100% for the PCT at a cut-off value of 
0.42%.
CONCLUSION: We determined that the platelet count and blood LDH level was high 
in the ET patient group with CALR mutation. Besides, we found that the blood 
haemoglobin level was higher in the ET patient group with JAK2 mutation. 
Additionally, the PCT level was higher in the CALR group when compared to the 
other patient groups.