Strengths and limitations of International Classification of Disease Ninth Revision Clinical Modification codes in defining cervical spine surgery.
METHODS
Retrospective study.


OBJECTIVE
To evaluate the sensitivity and specificity of International Classification of Disease Ninth Revision Clinical Modification (ICD9-CM) hospital discharge codes to define degenerative cervical spine surgery in comparison to patient operative notes in the medical record.


BACKGROUND
Population-based studies of spine surgery have often relied on administrative databases as a primary information source, but little is known about the validity of using ICD9-CM codes to identify these operations.


METHODS
We performed a retrospective study comparing ICD9-CM billing codes to patient operative notes, the gold standard, for patients undergoing spine surgery in 2006 at a single academic center.


RESULTS
We identified 1090 procedures of which 265 were categorized as cervical spine surgery for degenerative indications based on the operative notes. Compared to operative notes, our ICD9-CM algorithm had high sensitivity and specificity for selecting surgery at the cervical spine level and cervical spine surgery for degenerative indications. Categorization of cases by procedure had high sensitivity and specificity for fusion and surgical approach (>95%). Categorization of cases by primary diagnosis was generally less accurate. Cervical spondylosis with myelopathy was the most sensitive primary diagnosis. Categorization of cases by procedure had high sensitivity and specificity for fusion and surgical approach (≥96%). However, diagnoses such as herniated disc and procedures such as laminectomy had low sensitivity but high specificity.


CONCLUSIONS
The use of our ICD9-CM algorithm to define spine surgery at the cervical spine level, and degenerative cervical spine surgery is highly accurate. Although specific diagnoses codes are mostly insensitive, an ICD9-CM algorithm can be used to study these procedures with reasonable precision.
Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, USA. mwang@mcw.edu
Marjorie C
MC
Wang
Purusottom W
PW
Laud
Melissa
M
Macias
Ann B
AB
Nattinger
D000046:Academic Medical Centers; D000465:Algorithms; D002574:Cervical Vertebrae / Q000601:surgery*; D057225:Data Mining / Q000706:statistics & numerical data*; D019992:Databases as Topic / Q000706:statistics & numerical data; D006801:Humans; D038801:International Classification of Diseases / Q000706:statistics & numerical data*; D008499:Medical Records / Q000706:statistics & numerical data; D019637:Orthopedic Procedures / Q000706:statistics & numerical data*; D010351:Patient Discharge / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013122:Spinal Diseases / Q000145:classification* / Q000175:diagnosis / Q000601:surgery*; D014922:Wisconsin