Zinc Protoporphyrin, Blood
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The porphyrins are intermediaries in the heme synthesis pathway.
When iron is not available for heme synthesis (eg, iron deficiency), zinc protoporphyrin (ZPP) accumulates within RBCs.
Lead inhibits several enzymes in the heme synthesis pathway and causes 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 poisoning in 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.
Evaluating iron deficiency
Monitoring treatment and environmental intervention of chronic lead poisoning
An elevated zinc protoporphyrin (ZPP) indicates impairment of the heme biosynthetic pathway.
In children, a blood lead level of >20 ug/dL and an ZPP level of >70 mcmol 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.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
No significant cautionary statements
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.
<70 mcmol ZPP/mol heme
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Stanton NV, Gunter EW, Parsons PJ, et al: Empirically determined lead-poisoning screening cutoff for the Protofluor-Z hematofluorometer. Clin Chem 1989;35(10):2104–2107
2. Rosen JF: Preventing Lead Poisoning in Young Children. US Public Health Service, Centers for Disease Control, Atlanta, GA, 1991
3. Occupational Safety and Health Administration: OSHA Lead Standard-Requirements from the General Industry Standards Lead (1910, 1025), from 29 CFR 1910, 1025, A.M. Best Safety and Security-2000. Available from URL: ambest.com/safety/osha/chap10g.html Retrieved March 2000
4. Centers for Disease Control and Prevention. Screening Young Children for Lead Poisoning. Guidance for State and Local Public Health officials. Atlanta, GA: US Dept of Health and Human Services. Public Health Service: November 1997 Available from URL: cdc.gov/nceh/lead/guide/guide97.htm