Determination of hepatic iron concentration in fresh and paraffin-embedded tissue: diagnostic implications

Determination of hepatic iron concentration (HIC) is essential for the evaluation of hereditary hemochromatosis. Occasionally, only paraffin-embedded liver biopsy specimens are available, or fresh biopsy specimens have been placed in saline for transport. This study aimed to describe a method for extraction of liver tissue from paraffin blocks, determine the accuracy of measurement of HIC in recovered tissue compared with fresh tissue, and determine the effect of immersion in saline on HIC.

HIC was measured in both fresh and deparaffinized liver specimens (n = 41). Accurate measurements were defined as either a normal result in both specimens or a result in the deparaffinized specimen that was within 30% of the fresh measurement.

Measurements of HIC in fresh and deparaffinized tissue showed an excellent linear relationship (r = 0.95). In deparaffinized samples > or = 0.4 mg, accurate measurements were seen in 24 out of 29 specimens, compared with 6 out of 12 specimens weighing < 0.4 mg (P < 0.01). The hepatic iron index calculated from results in deparaffinized samples > or = 0.4 mg correctly classified all patients. Immersion of fresh biopsy specimens in saline for 1 hour resulted in up to 50% iron loss (P < 0.05).

Accurate measurement of HIC in deparaffinized liver biopsy specimens is possible. Calculation of the hepatic iron index from deparaffinized liver tissue can facilitate diagnosis of hemochromatosis when fresh tissue is not available. Samples should not be transported in saline.