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Interpretive Handbook

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Test 60764:
Iron/Creatinine Ratio, Random, Urine

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Iron is cleared primarily by biliary excretion via the feces. Renal clearance of iron is a secondary and relatively minor route of clearance. Excessive accumulation of iron in iron-overload diseases leads to higher than normal urine concentration of iron, known as hemosiderinuria.

Useful For Suggests clinical disorders or settings where the test may be helpful

Diagnosis of hemochromatosis, hemolytic anemia, paroxysmal nocturnal hemoglobinemia, and impaired biliary clearance

Interpretation Provides information to assist in interpretation of the test results

Normal excretion of iron occurs at the rate of approximately 100 mcg/day to 300 mcg/g creatinine. In the event that dietary iron is below minimum daily requirements (<2 mg/g creatinine in females, <1 mg/g creatinine in males), urinary excretion will be less than normal.

 

Urinary iron is greater than normal in iron overload. It is not uncommon to observe iron excretion >20,000 mcg/g creatinine in a patient with clinically evident hemochromatosis. Daily urine output of iron ranging from 500 mcg to 5,000 mcg suggests active hemolytic anemia, early-stage hemochromatosis, or impaired biliary clearance.

 

Because iron elimination undergoes extreme diurnal variation (serum levels 10 times higher in am than pm), collection of random specimens can cause very misleading interpretation.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Because iron elimination undergoes extreme diurnal variation (serum levels 10 times higher in am than pm), results from random urine specimens can be very misleading and are of limited value.

 

High concentrations of gadolinium and iodine are known to interfere with most metals tests. If either gadolinium- or iodine-containing contrast media has been administered, a specimen must not be collected for 96 hours.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

> or =16 years: 100-300 mcg/g Creatinine

Reference values have not been established for patients that are <16 years of age.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Gurzau ES, Neagu C, Gurzau AE: Essential metals--case study on iron. Ecotoxicol Environ Saf 2003 Sep;56(1):190-200

2. Ludwig J, Batts KP, Moyer,TP, Poterucha JJ: Advances in liver biopsy diagnosis. Mayo Clin Proc 1994 Jul;69(7):677-678