Hows porphyria cutanea tarda diagnosed?

See below. The preferred screening test for pct is a measurement of porphyrins in plasma. This can differentiate pct from variegate porphyria. The patterns of porphyrins in urine (predominately uroporphyrin and 7-carboxylate porphyrin) and feces (predominately isocoproporphyrin) help to confirm the diagnosis. The presence of an inherited deficiency of urod can be demonstrated by measuring the enzyme in rbcs.