Zinc Protoporphyrin, Blood

CPT CODE:

USEFUL FOR:

Evaluating iron deficiency
Monitoring treatment and environmental intervention of chronic lead poisoning

SPECIMEN REQUIRED:

Draw blood in a lavender-top (EDTA) tube(s), and send 1 mL of EDTA whole blood refrigerated. Specimen cannot be frozen.

TRANSPORT TEMPERATURE:

Refrig\Ambient NO\Frozen NO

CLINICAL INFORMATION:

The porphyrins are intermediaries in the heme synthesis pathway.
When iron is not available for heme synthesis (e.g., iron deficiency),zinc protoporphyrin (ZPP) accumulates within red blood cells (RBC).
Lead inhibits several enzymes in the heme synthesis pathway andcauses increased levels of RBC ZPP.
ZPP is a biological marker of lead toxicity and was previously used,in conjunction with blood lead assays, to screen for lead poisoningin children. However, because of poor sensitivity and specificity, ZPP is no longer recommended for lead screening in children.However, ZPP remains a useful tool for monitoring treatment of individuals with confirmed elevated lead levels.

CLINICAL INTERPRETATION:

An elevated ZPP indicates impairment of the heme biosyntheticpathway.
In children, a blood lead level of >20 ug/dL and an ZPP levelof >70 umol ZPP/mol heme are indicative of lead toxicity.(1)
Elevated ZPP levels in adults may indicate long-term (chronic)lead exposure or may be indicative of iron deficiency anemia or anemia of chronic disease.

REFERENCE VALUES:

<70 umol ZPP/mol heme