Ferritin concentrations in dried serum spots prepared by standard compared with simplified approaches: a validation study in Guatemala City

BACKGROUND: Spot ferritin assay on dried serum spot (DSS) samples provides reliable and accurate assessment. Standard DSS preparations, however, involve precise serum aliquots and require some skill and training of field personnel. OBJECTIVE: We evaluated the validity of the spot ferritin assay on DSS samples prepared by simplified approaches and standard technique in Guatemala City. DESIGN: Venous blood (5 mL) was obtained from 104 subjects aged 24 +/- 15 y (x +/- SD) and transferred into nonheparin-containing (2 plain and 2 self-sealing) capillary blood collection tubes. Three DSS samples were prepared: A (standard, 20 microL serum), B (blot, approximately 30-35 mm serum column), and C (dispenser, 20 microL serum pushed directly from self-sealing capillary tubes with a dispenser). Spots were air-dried and placed in hermetic plastic bags with a desiccant. Two weeks later, entire spots for DSS A and C samples and a circle in the center for DSS B samples were analyzed. RESULTS: DSS ferritin A, B, and C correlated strongly with traditional ferritin (r = 0.71-0.88, P < 0.001). The geometric mean (-1 SD and +1 SD) values for the DSS A, B, and C and traditional ferritin methods were 27.5 (12.6, 60.2), 32.4 (13.5, 77.6), 27.5 (11.7, 64.6), and 30.2 (13.8, 66.1) microg/L, respectively, and did not differ significantly. The difference in ferritin values by various DSS approaches compared with the traditional approach was small (<4 microg/L; P > 0.05). CONCLUSIONS: Simplified and standard DSS methods provide accurate iron-status assessment in population studies. The simplified DSS approaches for serum ferritin measurement need to be evaluated further in populations in whom iron deficiency is prevalent.