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A community outreach lead screening program using capillary blood collected on filter paper
T G Holtrop1, H Y Yee, P M Simpson
1Department of Pediatrics, Children's Hospital of Michigan, Wayne State University School of Medicine, Detroit 48201, USA.
Insights
Fingerstick blood collection on filter paper is a practical alternative for screening lead exposure in children. This method accurately identifies elevated blood lead levels, especially at the 0.48 micromol/L cutoff.
Area of Science:
- Environmental Health
- Pediatric Toxicology
- Clinical Chemistry
Background:
- Environmental lead contamination poses significant health risks, particularly to children.
- Accurate and accessible screening methods are crucial for early detection and intervention.
- Traditional venous blood sampling can be invasive and challenging in field settings.
Purpose of the Study:
- To evaluate the efficacy of fingerstick blood collection onto filter paper as an alternative screening method for lead exposure.
- To assess the accuracy of filter paper blood lead level (BLL) measurements compared to venous blood samples.
- To determine the suitability of this method in high-risk environments with potential lead contamination.
Main Methods:
- Paired venous and capillary blood samples were collected from 120 children (6 months to 6 years) in high-risk Detroit neighborhoods.
- Blood lead content was analyzed using graphite furnace atomic absorption spectrometry.
- Concordance, sensitivity, specificity, and predictive values were calculated for filter paper samples against venous samples at various cutoffs.
Main Results:
- Filter paper samples showed high concordance (0.96) with venous samples at a cutoff of 0.48 micromol/L (10 microg/dL).
- Sensitivity (94%) and specificity (99%) were excellent at the 0.48 micromol/L cutoff, with a positive predictive value of 97%.
- Accuracy decreased at higher cutoffs (0.72 micromol/L), with underreporting observed, though specificity remained high.
Conclusions:
- Capillary filter paper sampling is an accurate and practical alternative to venous sampling for blood lead screening, particularly at the 0.48 micromol/L cutoff.
- The method is highly specific for lead detection across tested cutoffs.
- Further investigation is needed to understand the discrepancies in reporting higher lead levels (≥0.72 micromol/L).
Objective:
To test whether a method of fingerstick blood sample collection onto filter paper could be used as an alternative screening method in the field in settings where environmental lead contamination is a high risk.
Method:
Members of the Pediatric Mobile Team of Children's Hospital of Michigan, Detroit, collected paired venous and capillary blood samples from 120 children, aged 6 months to 6 years, who presented for services at any of 7 sites located in decaying neighborhoods of older sections of Detroit. All samples were analyzed for lead content by graphite furnace atomic absorption spectrometry.
Results:
When filter paper samples with blood lead levels of 0.48 micromol/L (10 microg/dL) or higher were compared with matched venous samples, the concordance coefficient was 0.96. The sensitivity and specificity of the filter paper samples relative to the venous samples for a cutoff of 0.48 micromol/L (10 microg/dL) or higher were 94% and 99%, respectively, with a positive predictive value of 97%. However, at a cutoff of 0.72 micromol/L (15 microg/dL), the sensitivity and specificity dropped to 75% and 98%, respectively, with filter paper samples underreporting blood lead values. At any cutoff point (0.48, 0.72, or 0.96 micromol/L [10, 15, or 20 microg/dL]), the filter paper method was highly specific for lead.
Conclusions:
Capillary filter paper sampling is an accurate and practical alternative to venous sampling for blood lead screening using 0.48 micromol/L (10 microg/dL) as the cutoff. The filter paper method predicts levels of 0.72 micromol/L (15 microg/dL) or higher less well. The cause of divergent values above 0.72 micromol/L (15 microg/dL) is not clear. Environmental contamination of capillary filter paper, however, does not seem to be an explanation.