Iron

Serum iron measurement is should only be requested in cases of suspected iron overdose; serum ferritin is a better indicator of assessment of iron stores.

In cases of iron overdose, levels taken at four hours post overdose give the best indication of the severity of poisoning; however treatment should not be delayed whilst waiting for serum iron results.  In patients with suspected severe poisoning, a sample should be taken immediately to confirm the history.

That administration of desferrioxamine renders assessment of serum iron unreliable.

Clinicians managing patients with suspected iron overdose are encouraged to discuss all cases with the National Poisons Information Service (0344 892 0111).

References:

  • Thompson et al. ‘Guidelines for laboratory analyses for poisoned patients in the United Kingdom’ Annals of Clinical Biochemistry 2014, Vol. 51(3) 312–325
  • Toxbase.org

Transferrin saturation

Transferrin saturation is calculated from measurement of serum iron and transferrin.   Transferrin saturation typically rises in iron overload and falls in iron deficiency.  An increase in dietary iron intake can cause transferrin saturation to rise.  Measurement of transferrin saturation is typically used in the investigation and monitoring of iron overload, such as that resulting from haemochromatosis.

A raised transferrin saturation should be repeated with a confirmed fasting serum sample, to exclude the effect of dietary iron.

References:

  • Kelly et al. ‘Interpreting iron studies’ BMJ 2017, 357:j2513
  • European Association for the Study of the Liver. ‘EASL Clinical Practice Guidelines for HFE Hemochromatosis’ 2010, Journal of Hepatology