Serum
ferritin concentration is a sensitive measure of body
iron stores. The aim of this study was to compare the performance of two commercially available
enzyme-linked immunoassays (ELISAs) for serum
ferritin: a widely used manual assay kit (Spectro
Ferritin MT), and a new fully automated assay (Immulite). We analyzed serum samples from Moroccan school-aged children (n=51) from a rural area with a high prevalence of
iron deficiency anemia (IDA). Four replicates of each sample were analyzed using both assays. For the manual method, the interassay repeatability was 24%, 22%, and 11%, and intraassay precision was 18.3%, 9.2%, and 9.1% at increasing serum
ferritin concentrations. Using the automated assay, the interassay repeatability was 7%, 6%, and 6%, and intraassay precision was 1.5%, 5.4%, and 5.5% at increasing serum
ferritin concentrations. The two assays were well correlated (y=1.16x+1.83; r=0.98). However, the limits of agreement (LOAs) were wide, particularly at low concentrations. A comparison of the assay results with recommended cutoffs for serum
ferritin generated sharply different estimates of the prevalence of
iron deficiency (ID) in the sample. We conclude that the automated assay has several potential advantages compared to the manual method, including better precision, less operator dependence, and faster sample through-put.