Searching for a needle in a haystack: use of ICD-9-CM codes in drug-induced liver injury.
OBJECTIVE
The aim of our study was to compare three search strategies using a computerized administrative database to identify cases of idiosyncratic drug-induced liver injury (DILI) due to amoxicillin/clavulanic acid, phenytoin, valproic acid, and isoniazid.


METHODS
In search 1, electronic medical records from patients seen between 1994 and 2004 with an ICD-9-CM code of acute liver injury were identified and cross-searched for the specific drug names in the dictation text. In search 2, all patients with an ICD-9-CM code of drug poisoning/overdose due to one of the four study drugs were identified. In search 3, patients with a poisoning code as well as an acute liver injury code were identified.


RESULTS
Review of the records from the 7,395 search 1 patients yielded 51 DILI cases (0.7%). In contrast, the 566 search 2 patients yielded only three DILI cases (0.5%). Finally, search 3 provided the greatest specificity but a low rate of detection with only two patients (3.9%) having DILI due to one of the four drugs.


CONCLUSIONS
Acute liver injury ICD-9-CM codes combined with a text search of the dictated medical record yielded the greatest number of DILI cases but was less specific than crossing acute liver injury and poisoning codes. Use of ICD-9-CM codes to identify rare adverse events like DILI remains problematic and highlights the need for prospective surveillance networks.
Jinjuvadia
Kartik
K
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan, USA.
Kwan
Wendy
W
Fontana
Robert J
RJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D019980:Amoxicillin-Potassium Clavulanate Combination / Q000009:adverse effects; D056486:Chemical and Drug Induced Liver Injury; D002648:Child; D002675:Child, Preschool; D064420:Drug-Related Side Effects and Adverse Reactions; D005260:Female; D006801:Humans; D007223:Infant; D038801:International Classification of Diseases; D007538:Isoniazid / Q000009:adverse effects; D008107:Liver Diseases / Q000453:epidemiology; D008297:Male; D016347:Medical Records Systems, Computerized; D008824:Michigan / Q000453:epidemiology; D008875:Middle Aged; D010672:Phenytoin / Q000009:adverse effects; D011159:Population Surveillance; D012680:Sensitivity and Specificity; D014481:United States / Q000453:epidemiology; D014635:Valproic Acid / Q000009:adverse effects
D014635:Valproic Acid; D010672:Phenytoin; D019980:Amoxicillin-Potassium Clavulanate Combination; D007538:Isoniazid