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Chapter 058. Anemia and Polycythemia (Part 12)

Approach to the Patient: Polycythemia As shown in Fig. 58-18, the first step is to document the presence of an increased red cell mass using the principle of isotope dilution by administering 51 Cr-labeled autologous red blood cells to the patient and sampling blood radioactivity over a 2-h period. If the red cell mass is normal (36 mL/kg in men, 32 mL/kg in women), serum EPO levels should be measured. If EPO levels are low or unmeasurable, the patient most likely has polycythemia vera. Ancillary tests that support this diagnosis include elevated white blood cell count, increased absolute basophil count, and thrombocytosis. A mutation in. | Chapter 058. Anemia and Polycythemia Part 12 Approach to the Patient Polycythemia As shown in Fig. 58-18 the first step is to document the presence of an increased red cell mass using the principle of isotope dilution by administering 51Cr-labeled autologous red blood cells to the patient and sampling blood radioactivity over a 2-h period. If the red cell mass is normal 36 mL kg in men 32 mL kg in women the patient has spurious polycythemia. If the red cell mass is increased 36 mL kg in men 32 mL kg in women serum EPO levels should be measured. If EPO levels are low or unmeasurable the patient most likely has polycythemia vera. Ancillary tests that support this diagnosis include elevated white blood cell count increased absolute basophil count and thrombocytosis. A mutation in JAK-2 Val617Phe a key member of the cytokine intracellular signaling pathway can be found in 70-95 of patients with polycythemia vera. Figure 58-18 Dr Relative üfylhrúc osls Ox tQ .affinity heiTlnijlntii unfairly Measure serum EPO levels Measure arterial O2 saivraiion Measure carboxyhemogtebin revels Dx Polycylhcmia Diagnostic evaluation ter twart nr lung disease e.g. COPO high attitude AV or intracardiac shunt Measure hemoglobin Oj affinity normal Spuroi l F UCi Aj. K spt C L. Br unv ld t H uv r SL. Lon DL. J rn on JL. Lorc l-to Jl W mr iT r frAíw íaj1 c- stfcFwrjbÎiiïcAiMi 17th Edition httpi ww easjimcdicint-.com Copyright Th McOriu-Hlli Comp n T. Tnt. All nghttv4n rv dií v- í-OS íGtüJ An approach to diagnosing patients with polycythemia. RBC red blood cell EPO erythropoietin COPD chronic obstructive pulmonary disease AV atrioventricular IVP intravenous pyelogram hct hematocrit. If serum EPO levels are elevated one attempts to distinguish whether the elevation is a physiologic response to hypoxia or is related to autonomous .