Polycythemia - Differential Diagnosis Algorithm Polycythemia itself isn’t a diagnosis. Like many things, it is a condition with an underlying cause. How we define polycythemia: - Male: Hb>16.5 g/dL, Hct>49% - Female: Hb>16.0 g/dL, Hct>48% Remember that a one-off value won’t cut it. Tempo and delta are key to dx. Look back in the chart. Is this new or a trend? If new, make sure you check at least one additional Hb AND make sure to account for potential hemoconcentration. We may ask why are there so many RBCs?! Instead, pause, and try asking, “what stimulates our body to produce more RBCs?” Erythropoeitin! a.k.a EPO. Check a level. While you’re waiting for the EPO level, check if your patient needs rx first and dx second. Too many cells in the circulation = risk of hyperviscosity. Ask some questions centered around the most frequently affected systems: neuro, heme (bleeding), CV Hyperviscous? Better call hematology. This patient may need urgent plasmapheresis, phlebotomy, or chemo. Not hyperviscous? Sweet, we have some time, let’s see what came of that EPO level. Most polycythemia comes in two general flavors: - EPO-independent (primary) -> something else is driving RBC production - EPO-dependent (secondary) -> something is ramping up EPO levels Primary polycythemias - Typical issue: mutations, EPO levels: realllly low. - Acquired: polycythemia vera (JAK2 V617F) and MPNs (MPL, CALR, also JAK2) - Inherited: honestly, this list is long and obscure, and I don't know. Look it up Secondary polycythemias - Typical issue: oxygen (delivery/sensing) vs tumor vs exogenous, EPO levels: normal/high - Chronic hypoxia & bad oxygen sensing (at kidneys) - Some tumors produce EPO - Some people put things into their bodies Note about secondary causes: Many of these conditions can be screened for with a good history! Even though you’ll do a good workup, think about common co-morbids that can drive this disease. Finally, it’s always a good idea to call your friendly neighborhood hematologist if you’ve made a diagnosis or if you’re stuck. As with many disease processes, there can be a spectrum and overlap. Best to have an expert around to help. Dr. Anand Jagannath @AnandJag1 #Polycythemia #Differential #Diagnosis #Algorithm #workup #hematology
