Use of zinc protoporphyrin measured by the Protofluor-Z hematofluorometer in screening children for elevated blood lead levels.
OBJECTIVE
To determine the usefulness of zinc protoporphyrin, as measured by the Helena Protofluor-Z hematofluorometer, for detecting elevated lead levels.


METHODS
Observational, descriptive review of laboratory records from a university toxicology laboratory.


METHODS
Inner-city university pediatric clinic and two affiliated community clinics in Chicago, Ill.


METHODS
Seven hundred seventy-five children younger than 7 years with paired lead-zinc protoporphyrin results.


RESULTS
Fifty-six percent had lead levels of at least 0.48 mumol/L and 8% had lead levels of at least 1.21 mumol/L. The sensitivity, positive predictive value, and negative predictive value of a zinc protoporphyrin level of 70 mumol/mol of hemoglobin for detecting a lead level of 0.48 mumol/L were 42%, 66%, and 50%, respectively, and for a lead level of 1.21 mumol/L were 74%, 18%, and 97%, respectively. Receiver operating characteristic curves demonstrated that for detecting lead levels of 0.48 mumol/L with zinc protoporphyrin, the probability of a true-positive result is close to that of a false-positive one.


CONCLUSIONS
Zinc protoporphyrin is not a reliable screening test for detecting low blood lead levels.
Rolfe
P B
PB
Department of Pediatrics, University of Illinois, Chicago 60612.
Marcinak
J F
JF
Nice
A J
AJ
Williams
R H
RH
D002641:Chicago / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D005069:Evaluation Studies as Topic; D005189:False Positive Reactions; D005470:Fluorometry / Q000379:methods / Q000592:standards*; D006454:Hemoglobins / Q000032:analysis; D006785:Hospitals, University; D006801:Humans; D007223:Infant; D007854:Lead / Q000097:blood; D007855:Lead Poisoning / Q000097:blood* / Q000453:epidemiology; D008403:Mass Screening / Q000379:methods / Q000592:standards*; D010044:Outpatient Clinics, Hospital; D015995:Prevalence; D011379:Prognosis; D011524:Protoporphyrins / Q000097:blood*; D012680:Sensitivity and Specificity; D016036:Seroepidemiologic Studies
D006454:Hemoglobins; D011524:Protoporphyrins; C017803:zinc protoporphyrin; D007854:Lead