In the ED, their vitals/exam are as above. Patient with H/H drop from *** to *** in the setting of ***. The differential for anemia is classically divided into two categories: underproduction of RBCs (RI <2%) and destruction of RBCs (RI >2%). Underproduction is further divided into three categories based on MCV: MCV <80 is microcytic (iron deficiency, chronic disease, thalassemia, sideroblastic, lead poisoning), MCV 80-100 is normocytic (chronic disease, blood loss, mixed IDA & folate/B12 deficiency, sideroblastic, decreased EPO production such as in chronic renal insufficiency/hypothyroidism/adrenal insufficiency/hypopituitarism, decreased bone marrow production such as in aplastic anemia/MDS/red cell aplasia, splenic sequestration), MCV >100 is macrocytic (B12 deficiency, folate deficiency, liver disease, ethanol, hypothyroidism, myelodysplastic syndrome, AML, reticulocytosis, drug induced [hydroxyurea, AZT, chemotherapy]). Destruction is further divided into extrinsic (MAHA, immune mediated such as warm autoimmune [CLL, lymphoma, SLE]/cold autoimmune [EBV, mycoplasma]/transfusion reactions/drugs, infections [babesia/malaria], toxins [lead/copper/bites]) with shortened RBC lifespan and intrinsic etiologies (SS, HbC, Thal, G6PD, HS, PNH) with normal RBC lifespan. In this patient, given a RI of *** and MCV of ***, the most likely cause/s are ***.
– Labs/Tests: POCT guaiac, Lactate, CBC w/ diff (trend CBC), CMP, PT/INR, T&S, reticulocyte count, iron studies (iron, TIBC, ferritin), haptoglobin, LDH, fibrinogen, folate, B12, TSH, UA, prepare *** units. Consider peripheral smear/Coomb’s test/tick studies/viral studies (HIV-1/2, HIV-1 viral load, EBV PCR, CMV PCR, parvovirus B19)/medication review as inpatient if indicated.
– Imaging: ***
– Treatments: Transfuse *** units, IV PPI BID if c/f GI bleeding, pain control as needed, antiemetics as needed
– Consults: GI as inpatient if for consideration of EGD +/- colonoscopy
– Dispo: Pending further testing

Pearls:
-with H/H >3:1 + MCV <80 suggesting IDA -high RDW may suggest mix of retics and microcytic disorder anisocytosis -If elevated ferratin in setting of acute infection, use reticulocyte hemoglobin -Hematocrit will not be accurate if hypochromia (low MCHC) -Think about using hct when polycythemia (want to think about viscosity) -3:1 ratio of hct : hgb (of ratio is off look at mchc because hct does not look at pallor) -so if hct of 40 and hgb of 10, hypochromic rbc -rdw looks to say is there variability in red cell size (get peripheral smear) (retics will be large) -look at mcv then look at rdw to make sure there isn’t wide variability -microcytic —> MCHC (hypochromic vs not hypochromic, which will tell iron deficiency)
-macrocytosis —> retic count (hyper vs hypo-proliferative disorder)
-if retics > 0.12 is an appropriate response to anemia