Development and validation of an epidemiologic case definition of epilepsy for use with routinely collected Australian health data.
OBJECTIVE
We report the diagnostic validity of a selection algorithm for identifying epilepsy cases.


METHODS
Retrospective validation study of International Classification of Diseases 10th Revision Australian Modification (ICD-10AM)-coded hospital records and pharmaceutical data sampled from 300 consecutive potential epilepsy-coded cases and 300 randomly chosen cases without epilepsy from 3/7/2012 to 10/7/2013. Two epilepsy specialists independently validated the diagnosis of epilepsy. A multivariable logistic regression model was fitted to identify the optimum coding algorithm for epilepsy and was internally validated.


RESULTS
One hundred fifty-eight out of three hundred (52.6%) epilepsy-coded records and 0/300 (0%) nonepilepsy records were confirmed to have epilepsy. The kappa for interrater agreement was 0.89 (95% CI=0.81-0.97). The model utilizing epilepsy (G40), status epilepticus (G41) and ≥1 antiepileptic drug (AED) conferred the highest positive predictive value of 81.4% (95% CI=73.1-87.9) and a specificity of 99.9% (95% CI=99.9-100.0). The area under the receiver operating curve was 0.90 (95% CI=0.88-0.93).


CONCLUSIONS
When combined with pharmaceutical data, the precision of case identification for epilepsy data linkage design was considerably improved and could provide considerable potential for efficient and reasonably accurate case ascertainment in epidemiological studies.
Department of Medicine, St Vincent's Hospital, The University of Melbourne, PO Box 2900, Fitzroy, 3065 Victoria, Australia. Electronic address: michael.tan@svha.org.au.
Michael
M
Tan
Department of Medicine, St Vincent's Hospital, The University of Melbourne, PO Box 2900, Fitzroy, 3065 Victoria, Australia.
Ian
I
Wilson
The University of Virginia, Charlottesville, VA, USA.
Vanessa
V
Braganza
Department of Medicine, St Vincent's Hospital, The University of Melbourne, PO Box 2900, Fitzroy, 3065 Victoria, Australia.
Sophia
S
Ignatiadis
Department of Medicine, St Vincent's Hospital, The University of Melbourne, PO Box 2900, Fitzroy, 3065 Victoria, Australia; Department of Clinical Studies, New Bolton Centre, School of Veterinary Medicine, University of Pennsylvania, 382 West Street Rd., Kennett Square, PA 19348, USA.
Ray
R
Boston
Department of Medicine, St Vincent's Hospital, The University of Melbourne, PO Box 2900, Fitzroy, 3065 Victoria, Australia.
Vijaya
V
Sundararajan
Department of Medicine, St Vincent's Hospital, The University of Melbourne, PO Box 2900, Fitzroy, 3065 Victoria, Australia.
Mark J
MJ
Cook
Department of Medicine, St Vincent's Hospital, The University of Melbourne, PO Box 2900, Fitzroy, 3065 Victoria, Australia.
Wendyl J
WJ
D'Souza
D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D000927:Anticonvulsants / Q000627:therapeutic use; D001315:Australia / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D016208:Databases, Factual; D004827:Epilepsy / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D038801:International Classification of Diseases; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013226:Status Epilepticus / Q000175:diagnosis; D055815:Young Adult
D000927:Anticonvulsants
Classification; Data linkage; Epilepsy; ICD-10AM; Validation