The adequacy of capillary specimens for determining whole blood lead

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.

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				K. Verebey, T. P. Moyer, D. E. Nixon, and O. K. Ash Filter Paper-collected Blood Lead Testing in Children The authors of the editorial cited above respond: Clin. Chem., July 1, 2000; 46(7): 1024 - 1028. [Full Text] [PDF]