Porphyrins, Qn, 24 Hr Ur.
Evaluate porphyrias, including those involving deficiencies of enzymes that are needed for heme synthesis and chemical porphyrias.
Urine (24-hour), protected from light
Increased urine porphyrin excretion may be secondary to other diseases (eg, hepatobiliary diseases), especially coproporphyrin excretion. These are secondary porphyrinurias. They lack increased urinary porphobilinogen or Δ-ALA, with the important exception of lead poisoning.2 The table provides an abbreviated overview of the porphyrias. Porphyrin fractionation of plasma can be done. Increases of urine porphyrins are found with congenital erythropoietic porphyria, acute intermittent porphyria, hereditary coproporphyria, variegate porphyria, and porphyria cutanea tarda.
12-mL plastic transport tube without preservative.
Instruct patient to void at 8 AM (or 8 PM) and discard the specimen. Then collect all the urine, including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM [or 8 PM] the following day). Mix well. Measure and record total urine volume on the test request form, along with the patient’s name, date, and time collection started and finished. Transfer required aliquot into an amber plastic transport tube with amber cap. (If amber transport tubes are unavailable, cover transport tube completely, top and bottom, with aluminum foil. Identify specimen with patient’s name directly on the amber transport tube and on the outside of the aluminum foil. Secure with tape.) Specimen must be kept refrigerated during transport.
Refrigerate and protect from light
Stored specimen not refrigerated; specimen exposed to light; acid preservative; pH <3
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