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Open Access Research article

External validation of a claims-based algorithm for classifying kidney-cancer surgeries

David C Miller12*, Christopher S Saigal345, Joan L Warren6, Meryl Leventhal7, Dennis Deapen7, Mousumi Banerjee89, Julie Lai5, Jan Hanley5 and Mark S Litwin10345

Author Affiliations

1 Department of Urology, University of Michigan, Ann Arbor, MI, 48109, USA

2 Center for Clinical Management Research, VA Ann Arbor Healthcare System, Ann Arbor, MI, USA

3 Department of Urology, University of California, Los Angeles, Los Angeles, CA, USA

4 Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, CA, USA

5 RAND Health, RAND Corporation, Santa Monica, CA, USA

6 Applied Research Program, National Cancer Institute, Bethesda Md, USA

7 Cancer Surveillance Program, University of Southern California, Los Angeles, CA, USA

8 Department of Biostatistics, University of Michigan School of Public Health, Ann Arbor, MI, USA

9 Comprehensive Cancer Center, University of Michigan, Ann Arbor, MI, USA

10 Department of Health Services, School of Public Health, University of California, Los Angeles, CA, USA

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BMC Health Services Research 2009, 9:92  doi:10.1186/1472-6963-9-92

Published: 6 June 2009

Abstract

Background

Unlike other malignancies, there is no literature supporting the accuracy of medical claims data for identifying surgical treatments among patients with kidney cancer. We sought to validate externally a previously published Medicare-claims-based algorithm for classifying surgical treatments among patients with early-stage kidney cancer. To achieve this aim, we compared procedure assignments based on Medicare claims with the type of surgery specified in SEER registry data and clinical operative reports.

Methods

Using linked SEER-Medicare data, we calculated the agreement between Medicare claims and SEER data for identification of cancer-directed surgery among 6,515 patients diagnosed with early-stage kidney cancer. Next, for a subset of 120 cases, we determined the agreement between the claims algorithm and the medical record. Finally, using the medical record as the reference-standard, we calculated the sensitivity, specificity, and positive and negative predictive values of the claims algorithm.

Results

Among 6,515 cases, Medicare claims and SEER data identified 5,483 (84.1%) and 5,774 (88.6%) patients, respectively, who underwent cancer-directed surgery (observed agreement = 93%, κ = 0.69, 95% CI 0.66 – 0.71). The two data sources demonstrated 97% agreement for classification of partial versus radical nephrectomy (κ = 0.83, 95% CI 0.81 – 0.86). We observed 97% agreement between the claims algorithm and clinical operative reports; the positive predictive value of the claims algorithm exceeded 90% for identification of both partial nephrectomy and laparoscopic surgery.

Conclusion

Medicare claims represent an accurate data source for ascertainment of population-based patterns of surgical care among patients with early-stage kidney cancer.