Final answer:
A blood test provides the most accurate assessment for lead poisoning, as it directly measures the blood lead level, with the CDC recommending blood lead level screening for children.
Step-by-step explanation:
When testing a child for lead poisoning, the most accurate assessment method is a blood test. This is because diagnosis is typically made by measuring the blood lead level. The Centers for Disease Control (CDC) recommends blood lead level screening, particularly for children between one and two years old, who are at higher risk due to behaviors such as putting objects in their mouths and absorbing a higher proportion of lead they consume. In adults, especially those in certain occupations like construction work or plumbing, regular testing might be required due to higher risk of exposure. The CDC has set the upper limit for blood lead in children at 5 µg/dl, and any level above this should prompt steps to reduce lead exposure.