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Test Code LAB0206446 Iron, Liver Tissue

Additional Codes

Mayo Test ID
FET

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

Diagnosis of hemochromatosis using liver tissue specimens

Testing Algorithm

For more information see Hereditary Hemochromatosis Algorithm.

Method Name

Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

Reporting Name

Iron, Liver Ts

Specimen Type

Liver Tissue


Necessary Information


Patient's date of birth is required to calculate iron index.



Specimen Required


Supplies: Metal Free Specimen Vial (T173)

Container/Tube:

Preferred: Mayo metal-free specimen vial

Acceptable: Paraffin block, with no more than 1 or 2 cuts previously made

Specimen Volume: 2 mg

Collection Instructions: Two mg of liver tissue are required. This is typically a piece of tissue from a 22-gauge needle biopsy at least 2 cm long. If an 18-gauge needle is used, the tissue must be at least 1 cm in length.

Additional Information: Paraffin blocks will be returned 7 days after analysis is complete.


Specimen Minimum Volume

Needle biopsy: See Specimen Required; 2 mm x 2 mm (punch): 0.3 mg by dry weight

Specimen Stability Information

Specimen Type Temperature Time Special Container
Liver Tissue Refrigerated (preferred)
  Ambient 
  Frozen 

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Reference Values

Iron

Males: 200-2,400 mcg/g dry weight

Females: 200-1,800 mcg/g dry weight

 

Iron Index

≥13 years: <1.0 mcmol/g/year

Reference values have not been established for patients that are younger than 13 years.

Interpretation

A hepatic iron concentration above 10,000 mcg/g dry weight is diagnostic for hemochromatosis.

 

Hepatic iron concentrations above 3000 mcg/g are seen when there is iron overload without cellular injury and cirrhosis. Hepatic iron concentrations greater than the reference range are associated with hemosiderosis, thalassemia, and sideroblastic anemia. Some patients with hepatitis or cirrhosis without significant fibrosis will have hepatic iron concentrations at the top end of normal or just slightly above the normal range.

 

Iron accumulates in the liver normally with aging. The hepatic iron index (HII) normalizes hepatic iron concentration for age. The HII is calculated from the hepatic iron concentration by converting the concentration from mcg/g to mcmol/g dry weight and dividing by years of age. The normal range for HII is less than 1.0.

-Patients with homozygous hemochromatosis have an HII above 1.9.

-Patients with heterozygous hemochromatosis often have an HII ranging from 1.0 to 1.9.

-Patients with hepatitis and alcoholic cirrhosis usually have an HII below 1.0, although a small percentage of patients with alcoholic cirrhosis have an HII in the range of 1.0 to 1.9.

-Patients with hemochromatosis who have been successfully treated with phlebotomy will have an HII below 1.0.

 

Liver specimens collected from patients with cirrhosis containing a high degree of fibrosis have results near the low end of the reference range, even though they will show significant iron staining in hepatocytes. While it is true that iron accumulates in hepatocytes in advanced alcoholic cirrhosis with fibrosis, there are relatively few hepatocytes compared to other inert (fibrotic) tissue, so the quantitative iron determination, which is expressed as microgram of iron per gram of dry weight tissues, yields a low result. Histologic examination of all tissue specimens should be performed to facilitate correct interpretation. When structural heterogeneity is apparent histologically, variation in measured iron should be anticipated. In approximately 2% of cases, a high degree of hepatic heterogeneity has been observed that makes quantitation highly variable.

Day(s) Performed

Monday, Thursday

Report Available

3 to 6 days

Specimen Retention Time

60 days

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

83540

LOINC Code Information

Test ID Test Order Name Order LOINC Value
FET Iron, Liver Ts 57028-3

 

Result ID Test Result Name Result LOINC Value
8350 Iron, Liver Ts 57028-3
7770 Hepatic Iron Index 49061-5
CentraCare Laboratory Services Additional Information:

Note:  If pathologic (histologic, tissue) exam is needed for CentraCare Laboratory Services, a separate biopsy must be collected and submitted in formalin, and a separate order is required.