Validation of ICD-9 Codes for Stable Miscarriage in the Emergency Department.
BACKGROUND
International Classification of Disease, Ninth Revision (ICD-9) diagnosis codes have not been validated for identifying cases of missed abortion where a pregnancy is no longer viable but the cervical os remains closed. Our goal was to assess whether ICD-9 code "632" for missed abortion has high sensitivity and positive predictive value (PPV) in identifying patients in the emergency department (ED) with cases of stable early pregnancy failure (EPF).


METHODS
We studied females ages 13-50 years presenting to the ED of an urban academic medical center. We approached our analysis from two perspectives, evaluating both the sensitivity and PPV of ICD-9 code "632" in identifying patients with stable EPF. All patients with chief complaints "pregnant and bleeding" or "pregnant and cramping" over a 12-month period were identified. We randomly reviewed two months of patient visits and calculated the sensitivity of ICD-9 code "632" for true cases of stable miscarriage. To establish the PPV of ICD-9 code "632" for capturing missed abortions, we identified patients whose visits from the same time period were assigned ICD-9 code "632," and identified those with actual cases of stable EPF.


RESULTS
We reviewed 310 patient records (17.6% of 1,762 sampled). Thirteen of 31 patient records assigned ICD-9 code for missed abortion correctly identified cases of stable EPF (sensitivity=41.9%), and 140 of the 142 patients without EPF were not assigned the ICD-9 code "632"(specificity=98.6%). Of the 52 eligible patients identified by ICD-9 code "632," 39 cases met the criteria for stable EPF (PPV=75.0%).


CONCLUSIONS
ICD-9 code "632" has low sensitivity for identifying stable EPF, but its high specificity and moderately high PPV are valuable for studying cases of stable EPF in epidemiologic studies using administrative data.
Highland Hospital of Alameda Health System, Department of Emergency Medicine, Oakland, California.
Kelly E
KE
Quinley
James Madison University, Harrisonburg, Virginia.
Ailsa
A
Falck
Perelman School of Medicine, University of Pennsylvania, Center for Clinical Epidemiology and Biostatistics, Philadelphia, Pennsylvania.
Michael J
MJ
Kallan
Perelman School of Medicine, University of Pennsylvania, Department of Emergency Medicine, Philadelphia, Pennsylvania.
Elizabeth M
EM
Datner
Thomas Jefferson University, Department of Emergency Medicine, Philadelphia, Pennsylvania.
Brendan G
BG
Carr
Perelman School of Medicine, University of Pennsylvania, Department of Obstetrics and Gynecology, Philadelphia, Pennsylvania.
Courtney A
CA
Schreiber
D000022:Abortion, Spontaneous / Q000175:diagnosis*; D000046:Academic Medical Centers; D000293:Adolescent; D000328:Adult; D004636:Emergency Service, Hospital / Q000458:organization & administration*; D005260:Female; D006801:Humans; D038801:International Classification of Diseases / Q000592:standards*; D011237:Predictive Value of Tests; D011247:Pregnancy; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D055815:Young Adult