Validation of a brief screening instrument for the ascertainment of epilepsy.
OBJECTIVE
To validate a brief screening instrument for identifying people with epilepsy in epidemiologic or genetic studies.


METHODS
We designed a nine-question screening instrument for epilepsy and administered it by telephone to individuals with medical record-documented epilepsy (lifetime history of >or=2 unprovoked seizures, n = 168) or isolated unprovoked seizure (n = 54), and individuals who were seizure-free on medical record review (n = 120), from a population-based study using Rochester Epidemiology Project resources. Interviewers were blinded to record-review findings.


RESULTS
Sensitivity (the proportion of individuals who screened positive among affected individuals) was 96% for epilepsy and 87% for isolated unprovoked seizure. The false positive rate (FPR, the proportion who screened positive among seizure-free individuals) was 7%. The estimated positive predictive value (PPV) for epilepsy was 23%, assuming a lifetime prevalence of 2% in the population. Use of only a single question asking whether the subject had ever had epilepsy or a seizure disorder resulted in sensitivity 76%, FPR 0.8%, and estimated PPV 66%. Subjects with epilepsy were more likely to screen positive with this question if they were diagnosed after 1964 or continued to have seizures for at least 5 years after diagnosis.


CONCLUSIONS
Given its high sensitivity, our instrument may be useful for the first stage of screening for epilepsy; however, the PPV of 23% suggests that only about one in four screen-positive individuals will be truly affected. Screening with a single question asking about epilepsy yields a higher PPV but lower sensitivity, and screen-positive subjects may be biased toward more severe epilepsy.
Ottman
Ruth
R
G.H. Sergievsky Center and Department of Neurology, College of Physicians and Surgeons, Mailman School of Public Health, Columbia University, New York, New York 10032, USA. ro6@columbia.edu
Barker-Cummings
Christie
C
Leibson
Cynthia L
CL
Vasoli
Vincent M
VM
Hauser
W Allen
WA
Buchhalter
Jeffrey R
JR
D000328:Adult; D000368:Aged; D004569:Electroencephalography; D004827:Epilepsy / Q000175:diagnosis* / Q000453:epidemiology; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D008910:Minnesota / Q000453:epidemiology; D011237:Predictive Value of Tests; D015995:Prevalence; D011594:Psychometrics; D015203:Reproducibility of Results; D012307:Risk Factors; D012640:Seizures / Q000175:diagnosis* / Q000453:epidemiology; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D014505:Urban Population / Q000706:statistics & numerical data
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