IQ following treatment of lead poisoning: a patient-sibling comparison.

Forty-seven children treated for lead poisoning (PbB 50 to 365 microgram/dl) were compared to siblings next in age (PbB less than 40 microgram/dl) by a battery of psychologic tests. Symptoms were present in 18 but none had frank encephalopathy. Physical and neurologic examinations revealed no residual damage. Mean psychologic test scores showed no significant difference between patients and controls except in the arithmetic subtest, in which patients' scores were not related to lead concentration. Intelligence tests failed to distinguish children successfully treated from their sibling controls.