FEP in the Diagnosis of Iron Deficiency and Iron Deficiency Anemia

Introduction: In our laboratory we have the hematofluorometer which measures the FEP (Free Erythrocyte Protoporphyrin). The general section recommends that this test be included in the screening of children at the 12-15 month age group, or whenever screening for anemia is done (eg teenaged girls, dietary issues, high risk social situations)

What is FEP and What Does it Test For? Measured by one drop of capillary blood with an instantaneous readout by the hematofluorometer. This instrument measures the amount of free unbound porphyrin which accumulates in iron deficiency as a result of decreased heme synthesis. Thus the higher levels of FEP are abnormal. (Normal: 30-70 umol Zprotoporphyrin/ mol heme; Abnormal: greater than 70). FEP identifies iron deficiency before it becomes iron deficiency anemia. In other words, the FEP is elevated in iron deficiency as well as in iron deficiency anemia.

Why is that important? While cognitive delays are must more severe in iron deficiency anemia, they also have been demonstrated to occur in iron deficiency. This was first identified in South America; confirmed in US, where math scores found to be lower in both groups - recent publication (Peds 2001;107: 1381-6.) If treatment of iron deficiency can occur prior to its becoming anemia, intellectual damage in children can be prevented. The incidence of iron deficiency in the US is on the rise: children aged 1-3 years: 10% iron def anemia; + 7% iron def – not anemic. (Archives Peds 1997;151:986-8)

Limitations of the test: Problems exist in the interpretation of an elevated FEP in children. Other problems that can elevate the FEP are: chronic lead poisoning, chronic disease, and hemolytic anemia have all been implicated in falsely positive FEPs. Anecdotally, we have found that some medications can elevate the FEP as well: Furadantin, Tegretol, seizure meds.

When Should Iron Be Prescribed?

	FEP	Hemoglobin	Treat with Iron?
Case 1	High	Normal	Yes
Case 2	High	Low	Yes
Case 3	Normal	Normal	No
Case 4	Normal	Low	No

Is the FEP test Indicated for Lead Screening?
In the 1980’s, the FEP test was used for lead screening. During that time the test was identified as a valuable screen for iron deficiency. During that time period, an abnormal lead level was considered to be over 25 ug/dl. However, in 1991, the CDC changed the level at which lead was considered elevated – to 10 ug/dl. Since the FEP test did not reliably identify leads under 15 ug/dl, it is no longer considered to be reliable for screening for lead. However, it can be a way to follow elevated leads.

Written 3/02

Department of Pediatrics | Medical College of Georgia
Please email comments, suggestions or questions to:
John T. Benjamin M.D., jbenj@mcg.edu

February 27, 2004

Medical College of Georgia
Department of Pediatrics A-Z Index MCG Home
Continuity Clinic Notebook:	Chapter 1: The Prenatal and Well Child Visit