seizure or not: is prolactin useful?

STUDY:
--200 patients with seizure-like activity, 109 ultimately diagnosed with seizure
--31% (of 200 patients) had abnormal prolactin (upper limit of normal ~30mg/dL)

--the numbers:

• sensitivity of this serum prolactin was 42%
• specificity was 82%
• positive predictive value (PPV) of 74%
• negative predictive value (NPV) of 54%
• overall accuracy of 60% in the diagnosis of seizure,
• likelihood ratio of 2.4

--their conclusion: "The measurement of serum prolactin is helpful as a confirmatory test, but not as screening test in the emergency department setting."


REVIEW ARTICLE:
--most studies used 2x baseline serum prolactin level as 'elevated'
--the numbers:

• pooled sensitivity for generalized tonic-clonic seizures (60.0%); for complex partial seizures (46.1%)
• pooled specificity was similar for both (approximately 96%)
• 2 Class II studies were consistent in showing prolactin elevation after tilt-test-induced syncope.

--their conclusion: "Elevated serum prolactin assay, when measured in the appropriate clinical setting at 10 to 20 minutes after a suspected event, is a useful adjunct for the differentiation of generalized tonic-clonic or complex partial seizure from psychogenic nonepileptic seizure among adults and older children (Level B). Serum prolactin assay does not distinguish epileptic seizures from syncope (Level B)"


META-ANALYSIS:
--usefulness of raised serum prolactin in diagnosing generalised tonic-clonic seizures (GTSC) in patients presenting to the ED after a single episode of syncope
--13 relevant studies only 3 met the criteria for evaluation

--the numbers: if a serum prolactin concentration is > 3x the baseline when taken within one hour of syncope, then...

• LR (likelihood ratio) of GTSC vs pseudoseizure = 8.92, sensitivity 0.62, specificity 0.89
• LR of GTSC vs. syncope = 4.60, sensitivity 0.71, specificity 0.85

10-SECOND TAKEAWAY:
--serum prolactin in seizure: not too useful in the ED
--generally poor sensitivity, better specificity, but only if tested early (~10-60 min s/p episode)

--so if you can draw it fast, and if its significantly elevated, it might be useful (a lot of if's), but if its low, doesn't mean it's not a seizure

--serum prolactin in seizure: not too useful in the ED

Reference(s): study, review, meta-analysis, picture