Ferritin in serum and urine: A pilot study

Abstract

Serum ferritin reflects total body iron stores, thus a low serum ferritin is used as a parameter of iron deficiency. In healthy adults in Japan, urine ferritin levels were about 5% of serum ferritin levels, with a correlation coefficient of 0.79. It is not known whether a low urine ferritin could serve as a non-invasive screen for iron deficiency. If so, this might be useful for neonates and young children, avoiding phlebotomy to screen for iron deficiency. However, for urinary ferritin screening to be feasible, ferritin must be measurable in the urine and correlate with serum ferritin. Testing should also clarify whether the iron content of ferritin in serum and urine are similar. In this pilot feasibility study we measured ferritin in paired serum and urine samples of healthy adult males, healthy term neonates, growing preterm neonates, and children who had very high serum ferritin levels from liver disorders or iron overload. We detected ferritin in every urine sample, and found a correlation with paired serum ferritin (Spearman correlation coefficient 0.78 of log₁₀-transformed values). These findings suggest merit in further studying urinary ferritin in select populations, as a potential non-invasive screen to assess iron stores.

Keywords: Ferritin; Iron; Iron deficiency; Serum; Urine.

Figure 1.

log₁₀-transformed ferritin concentrations in paired serum/urine collections from five groups, each represented by a different symbol: healthy adult males (closed circle; n=5), term neonates (open square; n=5), stable, growing, preterm neonates in a NICU (closed triangle; n=8), neonates with very high serum ferritin levels (open circle; n=5) and one child with iron-overload and beta-thalassemia (closed square). The straight line is an “identify” line showing the relationship between serum and urine ferritin. The Spearman correlation coefficient of the log₁₀ values is 0.78.