Routine screening of blood and urine for severe reactions to anticonvulsant drugs in asymptomatic patients is of doubtful value.

Severe or fatal reactions to anticonvulsant agents are fortunately rare. We examined the value of routine screening of blood and urine to detect early signs of such reactions in asymptomatic patients. The basic assumptions of this type of screening program have been faulty or unproven, and the results of studies, although not definitive, have not supported the value of such programs. Our recommendations, approved by the Canadian Association for Child Neurology, suggest that asymptomatic patients not undergo routine screening of blood and urine but, rather, be informed of the early symptoms of severe toxic reactions and be asked to report them immediately to a physician.