Sensitivity and specificity of paired capillary prolactin measurement in diagnosis of seizures

Serum prolactin levels may increase after epileptic seizures, but the increase is transient. We developed an assay of prolactin from capillary blood applied to filter paper than can be performed at home. Blood was obtained by finger stick 15 and 75 min after a seizure-like clinical episode in 50 patients undergoing video-EEG monitoring. A positive result by immunoradiometric assay (IRMA) was set at a level greater than or equal to 6.7 ng/ml 15 min after a neurologic event or at a twofold decrease from 15 to 75 min. In all, 25 of 36 epileptic events and 1 of 14 nonepileptic events generated capillary prolactin levels >6.7 ng/ml, for a sensitivity of 69% and a specificity of 93%. If simple partial seizures were excluded, sensitivity increased to 80%. A twofold decrease from 15 to 75 min occurred in 25 of 36 epileptic events and in 2 of 14 nonepileptic events, for a sensitivity of 69% and a specificity of 86%. Paired capillary blood testing for prolactin is useful for diagnosis of seizures; results are comparable to those obtained by venous sampling. In our study group, assays of a second finger stick obtained 1 h after the first did not increase the sensitivity or specificity of the test. Our results suggest that capillary blood finger stick for prolactin is useful for diagnosis of seizures.