Below is an instruction that describes a task. Write a response that appropriately completes the request. ### Instruction: Hi! I wasnt tested for an MPL mutation, just CALR, JAK2, and BCR-ABL. The left shift was still there in my last blood test in late September. Not sure if it has been a left shift the whole time but in my past records (over 9 yes) my WBC is almost always elevated in addition to my platelets.. ### Response: You might try asking for a MPL mutation test (can be done from DNA extracted from your peripheral blood or bone marrow aspirate). Also, do you know if your CALR test was done by PCR and electrophoresis, or sequencing (i.e., next generation sequencing, NGS)? The PCR + electrophoresis method can usually identify but not characterize atypical mutations (i.e., not type 1 or type 2), whereas NGS can identify and characterize any mutations. Only about 1/8 of essential thrombocythemias are "triple negative" (lacking mutations in JAK2, CALR, and MPL).Another angle would be trying again to get a bone marrow biopsy and see what that shows..