title: Chiari malformation Type I surgery in pediatric patients. Part 1: validation of an ICD-9-CM code search algorithm.
abstract: OBJECTIVE Administrative billing data may facilitate large-scale assessments of treatment outcomes for pediatric Chiari malformation Type I (CM-I). Validated International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code algorithms for identifying CM-I surgery are critical prerequisites for such studies but are currently only available for adults. The objective of this study was to validate two ICD-9-CM code algorithms using hospital billing data to identify pediatric patients undergoing CM-I decompression surgery. METHODS The authors retrospectively analyzed the validity of two ICD-9-CM code algorithms for identifying pediatric CM-I decompression surgery performed at 3 academic medical centers between 2001 and 2013. Algorithm 1 included any discharge diagnosis code of 348.4 (CM-I), as well as a procedure code of 01.24 (cranial decompression) or 03.09 (spinal decompression or laminectomy). Algorithm 2 restricted this group to the subset of patients with a primary discharge diagnosis of 348.4. The positive predictive value (PPV) and sensitivity of each algorithm were calculated. RESULTS Among 625 first-time admissions identified by Algorithm 1, the overall PPV for CM-I decompression was 92%. Among the 581 admissions identified by Algorithm 2, the PPV was 97%. The PPV for Algorithm 1 was lower in one center (84%) compared with the other centers (93%-94%), whereas the PPV of Algorithm 2 remained high (96%-98%) across all subgroups. The sensitivity of Algorithms 1 (91%) and 2 (89%) was very good and remained so across subgroups (82%-97%). CONCLUSIONS An ICD-9-CM algorithm requiring a primary diagnosis of CM-I has excellent PPV and very good sensitivity for identifying CM-I decompression surgery in pediatric patients. These results establish a basis for utilizing administrative billing data to assess pediatric CM-I treatment outcomes.
authors.affiliation: Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee; 
authors.forename: Travis R
authors.initials: TR
authors.lastname: Ladner
authors.affiliation: Departments of 2 Neurological Surgery.
authors.forename: Jacob K
authors.initials: JK
authors.lastname: Greenberg
authors.affiliation: Department of Neurosurgery, Columbia University Medical Center, New York, New York.
authors.forename: Nicole
authors.initials: N
authors.lastname: Guerrero
authors.affiliation: Medicine.|Surgery, and.
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Olsen
authors.affiliation: Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee; 
authors.forename: Chevis N
authors.initials: CN
authors.lastname: Shannon
authors.affiliation: Departments of 2 Neurological Surgery.
authors.forename: Chester K
authors.initials: CK
authors.lastname: Yarbrough
authors.affiliation: Otolaryngology-Head and Neck Surgery, Washington University School of Medicine in St. Louis, Missouri; and.
authors.forename: Jay F
authors.initials: JF
authors.lastname: Piccirillo
authors.affiliation: Department of Neurosurgery, Columbia University Medical Center, New York, New York.
authors.forename: Richard C E
authors.initials: RC
authors.lastname: Anderson
authors.affiliation: Department of Neurosurgery, Columbia University Medical Center, New York, New York.
authors.forename: Neil A
authors.initials: NA
authors.lastname: Feldstein
authors.affiliation: Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee; 
authors.forename: John C
authors.initials: JC
authors.lastname: Wellons
authors.affiliation: Departments of 2 Neurological Surgery.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Smyth
authors.affiliation: Departments of 2 Neurological Surgery.
authors.forename: Tae Sung
authors.initials: TS
authors.lastname: Park
authors.affiliation: Departments of 2 Neurological Surgery.
authors.forename: David D
authors.initials: DD
authors.lastname: Limbrick
mesh_terms: D000293:Adolescent; D000465:Algorithms; D001139:Arnold-Chiari Malformation / Q000601:surgery*; D002648:Child; D002675:Child, Preschool; D015986:Confounding Factors, Epidemiologic; D016208:Databases, Factual; D019299:Decompression, Surgical; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D007223:Infant; D038801:International Classification of Diseases; D007796:Laminectomy; D008297:Male; D015146:Midwestern United States; D009511:New England; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D015144:Southeastern United States; D016896:Treatment Outcome
keywords: CM = Chiari malformation; CM-I = CM Type I; CM-II = CM Type II; CPT = Current Procedural Terminology; CU = Columbia University; Chiari malformation Type I; IDC-9-CM = International Classification of Diseases, Ninth Revision, Clinical Modification; IQR = interquartile range; PPV = positive predictive value; VU = Vanderbilt University Medical Center; WU = Washington University Medical Center; administrative data research; health services research; neurosurgery; validation studies