Comparison of zinc protoporphyrin and free erythrocyte protoporphyrin in whole blood.

Health Lab Sci. 1977 Apr; 14(2):126-8.HL

The recent change in emphasis from blood lead to erythrocyte protoporphyrin as the primary diagnostic test for screening for childhood lead poisoning has made it desirable to develop the quantitative relationship between the two protoporphyrins, free erythrocyte protoporphyrin (FEP) and zinc protoporphyrin (ZP), that are now widely used for screening purposes. ZP was found to be equal to 1.4 EP, thus permitting the measurement of either parameter, and its conversion to the other.