To the Editor In a JAMA Diagnostic Test Interpretation article, Drs Scherber and Mesa outlined the diagnostic steps in evaluation of an elevated hemoglobin level.1 We agree that JAK2 V617F gene mutation testing is among the options in the diagnostic algorithm for elevated hemoglobin, even in the presence of low-normal serum erythropoietin levels, because prompt treatment of polycythemia vera is warranted to reduce thrombotic risk. Contrary to the authors’ statements, however, testing for JAK2 mutations is usually done on peripheral blood rather than plasma, and test results are typically reported as either positive or negative (qualitative). Quantitative values are difficult to interpret because there is no standard analytic method of measurement and there are no interlaboratory calibrators. Numeric thresholds for acting on mutant allele burden are not well established.
Reeves BN, Gulley ML. Evaluating Elevated Hemoglobin. JAMA. 2016;316(10):1114-1115. doi:10.1001/jama.2016.11326