title: Validation of use of annular once-punched filter paper bloodspot samples for repeat lead testing.
abstract: BACKGROUND
  Lack of a second sample often precludes the ability to perform repeat lead measurements on filter paper bloodspot samples. We investigated whether annular specimens remaining from once-punched filter paper bloodspot specimens could provide accurate Pb measurements when measurements were scaled for the remainder area relative to the original punch area.
  
  
  METHODS
  50 microl bloodspot specimens were prepared using Pb-spiked EDTA whole blood. After removal of 6 mm punches, bitmap images of the remainder specimens were obtained using a scanner. Image analysis was used to determine the bloodspot area of the remainder sample relative to the area of the original punch. Measurement of Pb for punches and for remainder specimens was performed by ICP-MS.
  
  
  RESULTS
  Area-corrected Pb measurements for remainder samples were significantly higher than for the punches, by an average factor of 1.52+/-0.12 (p<0.05, n=28). The difference was due to a discontinuity (an increase) in the per-area Pb at the bloodspot perimeter. Area-corrected results for annular specimens that excluded the perimeter were identical to those of the punch.
  
  
  CONCLUSIONS
  Area-corrected Pb measurement using annular once-punched bloodspot remainder specimens can accurately reproduce lead measurements obtained from the original punch when the bloodspot perimeter area is excluded.
authors.affiliation: Nebraska Public Health Laboratory, Omaha, NE 68198-3135, USA.
authors.forename: Dana F
authors.initials: DF
authors.lastname: El-Hajjar
authors.forename: Katherine H
authors.initials: KH
authors.lastname: Swanson
authors.forename: James D
authors.initials: JD
authors.lastname: Landmark
authors.forename: Douglas F
authors.initials: DF
authors.lastname: Stickle
mesh_terms: D003116:Color; D005374:Filtration; D007854:Lead / Q000097:blood*; D010209:Paper
chemical_list: D007854:Lead