A filter-paper assay for serum ferrjtin

Serum ferritin (ferr) is often used as the most sensitive indicator of iron status. A "Spot-ferr" method for assessing iron status may be advantageous because samples may be collected by capillary sampling saving cost and concerns associated with venopuncture and ease in storage and handling. Serum samples (20 pJ) were spotted on filter paper (n=47) and kept frozen until analysis. On the day of the assay, spot samples were allowed to thaw to room temperature, incubated in a buffer containing cellulase, centrifuged, and ferr was assayed in the supernatant by a radioimmunoassay (RIA). Serum samples from these individuals (n=47) were also measured by the traditional RIA. Further, 10 serum samples ranging in ferr from 10-185 ng/ml were spotted and stored under 3 different conditions (room temperature, refrigerated, or frozen) for 2 wk prior to assay by the spot-ferr method. Our preliminary results indicate that the spot-ferr method correlated well with the traditional method (r=0.99, p=.0001). The geometric mean (±1SD) for ferr (n=47) was 49 (12-200) by the traditional vs 53 (12-235) ng/ml by the spot-ferr method (t=l .8, p=. 19). However, the spot-ferr method gave 7.4% higher values than the traditional method (paired t=2.2, p<.05). There were no differences in ferr from spot samples stored under different conditions (p>0.05). The spot-ferr method may offer a practical screening tool for field studies.