Anemia Diagnostic Workup

Algorithm Steps

1. ▶

   Start

   Anemia Detected

   Hgb <13 g/dL (men) or <12 g/dL (women)

   1. ●

      Action

      Initial Labs

      Complete evaluation

      • CBC with indices (MCV, MCH, MCHC, RDW)
      • Reticulocyte count
      • Peripheral smear
      • Basic metabolic panel (renal function)
      1. ◆

         Decision

         MCV Classification

         Key to differential diagnosis

         • Microcytic: MCV <80 fL
         • Normocytic: MCV 80-100 fL
         • Macrocytic: MCV >100 fL
         1. ●

            Action

            Microcytic Anemia (MCV <80)

            Check iron studies first

            • Iron, ferritin, TIBC, transferrin saturation
            • Think: TICS - Thalassemia, Iron deficiency, Chronic disease, Sideroblastic
            1. ◆

               Decision

               Iron Studies Pattern

               Ferritin and TIBC interpretation

               • Low ferritin = iron deficiency
               • High ferritin, low iron = chronic disease
               • Normal iron studies = thalassemia screen
               1. ●

                  Action

                  Iron Deficiency Anemia

                  Low ferritin (<30), high TIBC

                  • Find source of blood loss
                  • GI workup if no obvious source (EGD/colonoscopy)
                  • GYN evaluation if menorrhagia
                  • Treat: oral iron (ferrous sulfate 325mg TID)
                  • Recheck Hgb in 4-8 weeks
               2. ●

                  Action

                  Anemia of Chronic Disease

                  High ferritin, low iron/TIBC

                  • Inflammatory block of iron utilization
                  • Treat underlying condition
                  • ESA if renal disease (EPO low)
                  • IV iron may help if functional iron deficiency
               3. ●

                  Action

                  Consider Thalassemia

                  Normal iron, microcytic, target cells

                  • Hgb electrophoresis
                  • Beta-thal trait: elevated HbA2
                  • Alpha-thal: genetic testing
                  • Usually no treatment needed for trait
         2. ●

            Action

            Normocytic Anemia (MCV 80-100)

            Most common; broad differential

            • Check reticulocyte count first
            • Renal function (EPO-related)
            • Consider: anemia of chronic disease, early iron deficiency, hemolysis, bone marrow
            1. ◆

               Decision

               Reticulocyte Count

               Bone marrow response

               • Low/normal retic: underproduction
               • High retic (>2%): hemolysis or blood loss
               1. ●

                  Action

                  Underproduction (Low Retic)

                  Bone marrow not responding

                  • Check EPO level
                  • Renal disease (low EPO)
                  • Chronic disease (inflammation)
                  • Consider bone marrow if unexplained
                  1. ⚠

                     Warning

                     Hematology Referral

                     When to refer

                     • Unexplained cytopenias
                     • Suspected bone marrow disorder
                     • Hemolysis workup
                     • Transfusion-dependent anemia
                     • Suspected MDS, aplastic anemia
               2. ●

                  Action

                  Hemolysis (High Retic)

                  Destruction of RBCs

                  • LDH elevated, haptoglobin low
                  • Indirect bilirubin elevated
                  • DAT (Coombs) for immune hemolysis
                  • Smear: spherocytes, schistocytes
         3. ●

            Action

            Macrocytic Anemia (MCV >100)

            B12/folate vs non-megaloblastic

            • Check B12, folate, TSH, LFTs
            • Reticulocyte count
            • Consider: alcohol, hypothyroidism, MDS, liver disease
            1. ◆

               Decision

               B12/Folate Levels

               Megaloblastic vs non-megaloblastic

               1. ●

                  Action

                  B12 Deficiency

                  B12 <200 pg/mL

                  • Check methylmalonic acid if borderline
                  • Causes: pernicious anemia, malabsorption, vegan diet
                  • Treat: B12 1000mcg IM daily x7d, then weekly x4, then monthly
                  • Or high-dose oral (1000-2000mcg daily)
               2. ●

                  Action

                  Folate Deficiency

                  Folate <3 ng/mL, normal B12

                  • Causes: poor intake, alcohol, malabsorption
                  • Treat: folic acid 1mg daily
                  • Rule out B12 deficiency first (can mask)
               3. ●

                  Action

                  Non-Megaloblastic Macrocytic

                  Normal B12/folate

                  • Alcohol (most common)
                  • Hypothyroidism
                  • Liver disease
                  • Reticulocytosis
                  • MDS, aplastic anemia (need BMBx)