CORRELATION BETWEEN JANUS KINASE 2 (JAK 2-V617F) POSITIVITY, LAP SCORE AND BONE MARROW FIBROSIS IN CASES OF THROMBOCYTOSIS

Abstract

Objective: Raised platelets count may result from essential thrombocythemia (ET) and also seen in cases of secondary thrombocytosis. It is essential to confirm the diagnosis of ET and differentiate it from secondary causes of raised platelet count. Molecular testing has become part of protocols in the diagnosis of myeloproliferative disorder including cases of thrombocytosis to confirm the diagnosis of ET. JAK2 V617F mutation is seen with a frequency of 55% in cases of ET and in many cases this mutation is negative. Molecular studies are very expensive and beyond the reach of majority of patients in developing countries.  The aim of present study is to establish correlation between JAK-2 positivity, Leucocyte Alkaline Phosphate (LAP score) and bone marrow fibrosis in the cases of thrombocytosis to confirm the diagnosis of Essential Thrombocythemia.

Material and Methods: Between Jan 2019 to August 2019, 27 patients with platelet counts more than 600x109/l were enrolled in the study. Median age was 56 (39-75) years, Male to Female ratio 3:1. Investigations carried out were blood complete picture, LAP score, bone marrow aspiration and trephine biopsy stained with both H&E and reticulin stain. PCR for JAK2 V6187F was performed on real time PCR.

Results: LAP score was raised (>150) in 22 cases, bone marrow fibrosis more than grade II was present in 20 cases. JAK2 V617F was positive in 20 cases. In this study cases with raised LAP score and  bone marrow fibrosis more than grade II JAK2 positivity was seen in 74% cases in contrast to 55% JAK2 V617F positivity seen in cases of thrombocytosis.

Conclusion: LAP score and bone marrow examination are cost-effective and widely available procedures at a District Head Quarter Hospitals are a sensitive indicator of JAKV617F positivity, the facility for molecular studies are available in a few specialized centers in the country and these studies are very expensive as well. These simple tests should be performed before proceedings to molecular studies.

Key Words: ET, JAK2V617F, LAP score, Bone marrow fibrosis.