The validity of prolactin measurements using capillary blood in the diagnosis of epilepsy was tested in the Departments of Neurology, Neurosurgery, and Pathology, The Johns Hopkins University School of Medicine, Baltimore, MD. Venous and capillary prolactin levels were determined 10 to 20 minutes after seizure-like episodes in 20 patients studied in an epilepsy monitoring unit. All patients had documentation of their seizure type by simultaneous video-EEG monitoring. Using the low criterion of elevation (18 ng/ml), capillary prolactin values were predictive of seizures versus pseudoseizures in 9 (100%) of 9 patients with generalized tonic-clonic patterns, in 5 (71%) of 7 patients with complex partial seizures, and 4 (100%) of 4 patients with pseudoseizures. Venous and capillary prolactin values correlated and were unaffected by leaving filter paper samples at room temperature for up to one week. 
COMMENT. Capillary blood collection for prolactin measurement may assist in the diagnosis of epilepsy in an outpatient clinic. Prolactin serum levels are elevated in children after tonic-clonic and complex partial seizures but determinations must be interpreted with reference to the complete clinical findings.