Clinical Diagnostics and Research tools
Human Free Erythrocyte Protoporphyrin (FEP) Assay
The Free Erythrocyte Protoporphyrin (FEO) test measures the non-complexed, non-heme protoporphyrin concentration in blood. This test alone is not sensitive enough to diagnose iron deficiency, but an elevated FEP in conjunction with a low MCV is suggestive.
FEP is measured using a thin smear of whole blood placed on a coverslip. The fluorometer measures the amount of free unbound porphyrin which accumulates in iron deficiency as a result of decreased heme synthesis. The intensity of the analytic signal produced by the instrument is a function of the molar ratio of fluorescing protoporphyrin to light-absorbing heme.(ref:Marsh WL Jr, Nelson DP, & Koenig HM: Free erythrocyte protoporphyrin (FEP) II. The FEP test is clinically useful in classifying microcytic RBC disorders in adults. Am J Clin Pathol 1983; 79(6):661-666)