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The adequacy of capillary specimens for determining whole blood lead
N H Johnson1, K O Ash, K L Nuttall
181 MIDOS/SHOKI, Clinical Research Laboratory, Keesler AFB, MS 39534, USA.
Insights
Capillary blood lead testing offers a reliable alternative to venous draws for children. While capillary results were slightly higher, meticulous protocols ensure accuracy for screening programs.
Area of Science:
- Pediatric Health
- Environmental Health
- Clinical Pathology
Background:
- Venous blood collection for lead level determination in children presents challenges.
- The Centers for Disease Control and Prevention (CDC) advocates for research into alternative capillary methodologies.
- Reliable alternatives are needed for accurate pediatric whole blood lead level assessment.
Purpose of the Study:
- To evaluate the adequacy of capillary blood specimens for determining whole blood lead levels in children.
- To compare blood lead results obtained from capillary and venous specimens.
- To assess the impact of handwashing on gross contamination and the reliability of follow-up capillary specimens.
Main Methods:
- Comparative analysis of blood lead results from paired capillary and venous specimens.
- Analysis of follow-up blood lead specimens from patients with initially elevated levels.
- Experimental assessment of handwashing effectiveness in reducing external lead contamination.
Main Results:
- A statistically significant difference was observed between mean venous (3.83 µg/dL) and capillary (4.6 µg/dL) lead levels (p < 0.005), though not clinically significant.
- Gross contamination of capillary specimens was infrequent.
- Handwashing demonstrated a significant reduction in external lead contamination.
- Follow-up capillary lead levels for patients with initially elevated results were generally low.
Conclusions:
- Capillary blood specimens are a viable alternative to venous specimens for whole blood lead screening in children.
- Strict adherence to prescribed collection protocols by both patient and collector is crucial for accurate capillary specimen collection.
- Confirmation of all elevated screening results (both capillary and venous) with a venous blood draw is recommended before initiating follow-up actions.
Abstract:
In response to demands for reliable alternatives to collection of venous specimens for determination of whole blood lead levels in children, the Centers for Disease Control has called for increased research into capillary methodologies. In this study, a three tiered approach was developed to assess the adequacy of capillary specimens for determining whole blood lead. Patient blood lead results from capillary and venous specimens were compared for obvious differences. Next, follow-up specimens for patients with elevated lead levels were compared with the initial results. In addition, experiments were conducted to determine whether or not handwashing eliminates gross contamination. Although the differences are not clinically important, the mean, 3.83 micrograms/dL for 5,100 venous specimens, was significantly lower (p < 0.005) then the mean of 4.6 micrograms/dL for 1,100 capillary specimens. Gross contamination was rare. Lead levels in follow-up specimens on patients whose initial screens were elevated were generally low. Handwashing greatly reduced the amount of external lead contamination. It is concluded that capillary specimens are an acceptable alternative to venous specimens for whole blood screening programs provided the patient and collector meticulously follow the prescribed collection protocol. Nevertheless, all elevated whole blood lead screening results, venous or capillary, should be confirmed with a venous collection before follow-up action is taken.