Erythrocyte Protoporphyrin

Aka: Erythrocyte Protoporphyrin, Free Erythrocyte Protoporphyrin, RBC Protoporphyrin, Protoporphyrin, Zinc Protoporphyrin, Free Protoporphyrin

1. Indications
   1. Low-cost clinic-based Iron Deficiency screening
   2. Lead Poisoning screening
2. Physiology
   1. Protoporphyrin converted to heme by ferrocheletase
   2. Lead inhibits ferrocheletase
      1. Protoporphyrin accumulates (ferrocheletase absent)
   3. Iron Deficiency results in impaired heme synthesis
      1. Protoporphyrin accumulates
3. Technique
   1. Hematofluorimeter measures Protoporphyrin
4. Efficacy
   1. Iron Deficiency Anemia
      1. Identifies cases of Iron Deficiency prior to Anemia
      2. Non-specific test (see causes for increase below)
      3. Misses some cases of Iron Deficiency Anemia
         1. Perform concurrently with Hemoglobin
      4. Similar to Transferrin Saturation
         1. Marks similar timing in Iron Deficiency
   2. Lead Poisoning
      1. Correlated with blood lead level
      2. See normal values below
5. Interpretation
   1. Normal range: 16 - 65 ug/dl (adults)
   2. Overt Iron Deficiency Anemia: Protoporphyrin >100
   3. Lead levels correlated with Protoporphyrin
      1. Protoporphyrin 79: Blood lead level 29
      2. Protoporphyrin 147: Blood lead level 49
      3. Protoporphyrin 255: Blood lead level 79
6. Increased
   1. Iron Deficiency Anemia
   2. Lead Poisoning
   3. Sideroblastic Anemia
   4. Chronic disease
   5. Hemolytic Anemia
   6. Erythropoietic protoporphyria
7. References
   1. Bakerman (1984) Interpretive Lab Data, p. 449
   2. Kazal (2002) Am Fam Physician 66(7):1217-27