An elevation of total RBC porphyrins can be an expression of a primary or secondary defect in the biosynthesis of heme. However, the specific type of porphyria cannot be determined by total porphyrin analysis alone.
Total RBC porphyrin values >80 mcg/dL suggest the existence of an intoxication problem or a metabolic problem that involves accelerated erythropoiesis. If the total RBC porphyrin concentration is elevated, additional testing (fractionation assays) is required to identify and quantify the specific affected porphyrin. Increased total RBC porphyrin concentrations may be due to:
-Free protoporphyrin, the predominant form that is elevated in patients with erythropoietic protoporphyria
-Zinc protoporphyrin, elevated in patients with heavy metal intoxication or iron deficiency anemia
-Uroporphyrin and coproporphyrin, preferentially elevated in patients with congenital erythropoietic porphyria
A written interpretation is included with all reports. When abnormal results are detected, a detailed interpretation is given, including:
-An overview of the results and their significance
-Elements of a differential diagnosis
-Recommendations for additional biochemical testing
A normal RBC porphyrin evaluation does not rule out other forms of porphyria including porphyria cutanea tarda (PCT), acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), and variegate porphyria (VP).