To ensure accurate, nationally representative sampling, the NHDS uses a complex three-stage probability design. Information collected in the survey included diagnosis and procedure codes (ie, International Classification of Diseases, ninth revision, clinical modification [ICD-9-CM]), age, sex, race, principal expected source of payment (ie, insurance status), length of care, hospital size, and patient discharge status. Weighted data, with weights derived from census data by the NHDS, are provided to generate unbiased national estimates from the sample (1% of all hospital discharges in the United States). Prior to 1988, different survey methods were used for NHDS. To avoid any potential bias introduced by the redesign, we only used data collected from 1988 forward.
Data collected for each year between 1988 and 2002 were obtained, read into a statistical software program (SAS, version 9; SAS Institute; Cary, NC), and concatenated. Patients with procedure codes (ICD-9-CM) for segmentectomy (32.3), lobectomy (32.4), and pneumonectomy (32.5) were included in the sample (Table 1). Patients under the age of 1 year were excluded. To simplify the analysis of temporal changes in lung resection procedures, three 5-year time periods were created (1988 to 1992,1993 to 1997, and 1998 to 2002). Changes in the prevalence of procedures were examined by time period. Changes in age, gender, race, length of care, distribution of procedures by hospital size, and disposition status were evaluated across time periods. The frequencies of procedure-related complications over time were analyzed by determining cases that listed ICD-9-CM diagnosis codes specifying complications of surgical and medical care, including complications peculiar to certain specific procedures (996.X), complications affecting specific body systems not elsewhere specified (997.X), other complications of procedures (998.X), and complications of medical care not elsewhere specified (999.X), as described previously.
Table 1—ICD-9-CM Procedure Codes for Lung Resection Surgery Included in This Study
|32.3||Segmental resection of lung; partial lobectomy|
|32.4||Lobectomy of lung; lobectomy with segmental resection of adjacent lobes of lung; excludes: that with radical dissection (excision) of thoracic structures (code 32.6)|
|32.5||Complete pneumonectomy; excision of lung NOS; pneumonectomy (with mediastinal dissection)|