The aim of the study was to evaluate the sensitivity, specificity and
the predictive values of repeated serum prolactin measurements in rela
tion to epileptic seizures versus pseudoseizures. The method used was
prospective measuring of serum prolactin from blood samples drawn (1)
15 min after seizure and (2) 2 hr after the first sample. Two paramete
rs were used: the absolute maximal level; and the relative rise in blo
od level. In the study 38 had epilepsy (simple or complex partial seiz
ures with or without secondary generalisation); and 20 had pseudo-epil
eptic seizures. In all cases, the diagnoses were made independent of t
he prolactin levels. In 30/38 (79%) of epilepsy patients and 17/20 (85
%) of pseudoseizure patients, the diagnoses were corroborated by inten
sive EEG monitoring (video or cassette telemetry). There was a statist
ically significant rise in prolactin levels in both groups (p<0.0001 a
nd <0.02, respectively), and also a significant difference between the
two groups. However, repeated measurements in a number of patients (e
pilepsy: mean 1.5 measurements; pseudo; mean 2.1) showed also consider
able intra-patient variations. The sensitivity for the maximal rise in
pseudoseizures (5.5x) was only 20% and the negative predictive value
40%. For the cut-off in absolute level (1025 mu U/ml), the correspondi
ng figures were 34% and 44%, respectively. The rather limited discrimi
native power of prolactin measurements makes it of questionable value
in discerning between epileptic and pseudo-epileptic seizures.