Utility of a Combined Current Procedural Terminology and International Classification of Diseases, Ninth Revision, Clinical Modification Code Algorithm in Classifying Cervical Spine Surgery for Degenerative Changes

Retrospective study. To evaluate the sensitivity and specificity of a combined Current Procedural Terminology (CPT) and International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) algorithm in defining cervical spine surgery in comparison to patient operative reports in the medical record. Epidemiological studies of spine surgery often use ICD-9-CM billing codes in administrative databases to study trends and outcome of surgery. However, ICD-9-CM codes do not clearly identify specific surgical factors that may be related to outcome, such as instrumentation or number of levels treated. Previous studies have not investigated the sensitivity and specificity of a combined CPT and ICD-9-CM code algorithm for defining cervical spine surgical procedures. We performed a retrospective study comparing the sensitivity and specificity of a combined CPT and ICD-9-CM code algorithm to the operative note, the gold standard, in a single academic center. We also compared the accuracy of our combined algorithm with our published ICD-9-CM-only algorithm. The combined algorithm has high sensitivity and specificity for defining cervical spine surgery, specific surgical procedures such as discectomy and fusion, and surgical approach. Compared to the ICD-9-CM-only algorithm, the combined algorithm significantly improves identification of discectomy, laminectomy, and fusion procedures and allows identification of specific procedures such as laminaplasty and instrumentation with high sensitivity and specificity. Identification of reoperations has low sensitivity and specificity, but identification of number of levels instrumented, fused, and decompressed has high specificity. The use of our combined CPT and ICD-9-CM algorithm to identify cervical spine surgery was highly sensitive and specific. For categories such as surgical approach, accuracy of our combined algorithm was similar to that of our ICD-9-CM-only algorithm. However, the combined algorithm improves sensitivity, and allows identification of procedures not defined by ICD-9-CM procedure codes, and number of levels instrumented and decompressed. The combined algorithm better defines cervical spine surgery and specific factors that may impact outcome and cost.