Stability of serum ferritin measured by immunoturbidimetric assay after storage at -80°C for several years.

Agreement between SF values before and after 3 to 5 years of constant freezing at -80°C was in a generally accepted range, which supports the hypothesis of ferritin's stability at this temperature for a long period. In long-term storage by freezing, intermediate thawing induced a major increase in values.