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Can statistics alone add clinical meaning to non-specific billing databases? Commentary on an article by Richard A. Deyo, MD, MPH, et al.: "Revision surgery following operations for lumbar stenosis".

Revision surgery after an operation for the treatment of lumbar stenosis is an undesired outcome. In an attempt to further understand the incidence of revision surgery after the initial treatment of lumbar spinal stenosis, the authors of the current paper used the Medicare Provider Analysis and Review (MedPAR) billing database from 1999 to 2008. As with any retrospective study relying on billing data to make appropriate clinical conclusions, one must recognize and understand the limitations of the potentially flawed and biased source data that have no easily verifiable inputs or controls. In this case, the authors just accepted the data as presented.

The MedPAR database contains information about all Medicare hospital claims submitted for reimbursement. Importantly, the database only contains broad, categorically based, facility ICD-9-CM billing codes selected by billing personnel after the fact rather than the surgeon-selected Healthcare Common Procedure Coding System (HCPCS) Level-I Current Procedure Terminology (CPT) code, which also does not always accurately reflect what was done. These data only reflect what is needed for hospitals to collect payments, and they include no other scientific or clinical facts or discussion of indications or techniques. The multicenter study from 1997 that was cited by the authors to support their analysis regarding the accuracy of coding indicated that seventeen of sixty-one patients who had undergone previous lumbar surgery actually had the appropriate code for the diagnosis1. The abstract states, “Although there were both false-negative and false-positive codes at each institution, most errors were related to the low sensitivity of coding for previous spinal operations: only seventeen (28 per cent) of sixty-one such diagnoses were coded correctly.”1

Newer studies evaluating the accuracy of ICD-9-CM-based databases have shown a similarly …