Tests for Lead Poisoning
A blood lead test can be done to detect the level of lead in your body. This is usually performed on a sample drawn from a vein in the arm but may sometimes be performed on a sample from a fingerstick or heelstick (for infants). If the fingerstick sample is abnormal, then it is frequently followed by a sample taken from the arm to confirm the findings. Blood lead levels are a snapshot of the amount of lead in the blood at that moment. They are the best test for detecting and evaluating recent acute and chronic exposure. Blood lead samples are used to screen for exposure and to monitor the effectiveness of treatment.
When a child's blood lead level is greater than 20 mcg/dL, the doctor may order a hemoglobin and/or hematocrit test to determine if the child is anemic and may order iron tests to check for iron deficiency.
The zinc protoporphyrin (ZPP) test is an old test that has fallen out of favor for general lead screening. ZPP increases when lead interferes with the red blood cells' ability to make hemoglobin. The ZPP test represents an average of lead exposure over time and is not affected by the location of lead in the body. It does not reflect recent exposure to lead; it falls more slowly than lead levels once the person is removed from the source of lead exposure, and it does not usually become abnormal until the lead concentration is greater than 25 micrograms per deciliter (mcg/dL). This means it is not sensitive enough to be useful as a screening test for children.