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Pharmacoepidemiol Drug Saf. 2002 Dec;11(8):709-13.

Use of ICD-9 coding as a proxy for stage of disease in lung cancer.

Author information

1
Department of Pharmacy Practice and Science, University of Maryland, Baltimore, MD, USA.

Abstract

OBJECTIVE:

To determine the validity of using ICD-9-CM codes indicating metastases as a proxy to classify lung cancer patients by stage of disease.

RESEARCH DESIGN:

This retrospective database analysis used diagnosis codes to classify subjects to either localized or advanced-stage disease and then compared this classification to the tumor registry staging, which was considered as the 'gold standard.'

SUBJECTS AND MEASURES:

Study subjects included all lung cancer patients treated at our academic institution during 1996-1997, who were also members of a large insurance company. Data were derived from inpatient cancer-related claims linked with our institution's tumor registry data. Advanced-stage disease (stages II to IV) was defined by claims indicating lymph node involvement or metastases (ICD-9 codes 196-199.1). The tumor registry stagings of the disease for these patients were clustered into two groupings, stages 0-I (localized) and stages II-IV (advanced).

RESULTS:

Tumor registry entries were identified for 66/77 (85.7%) patients. A total of 19 out of 22 local disease patients (sensitivity of 86.4%) and 30 out of 44 advanced disease patients (sensitivity of 68.2%) were classified correctly by ICD-9 code. A total of 19 out of 33 patients with local disease codes (PPV of 57.6%) and 30 out of 33 patients with advanced disease codes (PPV = 90.9%) were properly identified.

CONCLUSIONS:

For a population of lung cancer patients in an academic institution who were under a private insurance plan, the ICD-9 coding was associated with a sensitivity and positive predictive values that were consistent with previously reported estimates using Medicare-SEER data. The use of such data to classify patients to disease stages should be executed with caution as under-reporting might exist. Continued attention to discharge abstracting will be needed to improve the validity of this technique.

PMID:
12512248
DOI:
10.1002/pds.759
[Indexed for MEDLINE]

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