Background: The use of administrative health data is increasingly common for the study of various medical and surgical diseases. The validity of diagnosis codes for the study of benign upper gastrointestinal disorders has not been well studied.
Methods: The authors abstracted the charts for 590 adult patients who underwent upper gastrointestinal endoscopy between January 1, 2000 and June 30, 2001 in Toronto, Ontario, Canada. Clinical diagnoses from medical records were compared with International Classification of Diseases Version 9 (ICD-9) codes in electronic hospital discharge abstracts. The primary analysis aimed to determine the sensitivity, specificity, and positive predictive value (PPV) of a most responsible "esophagitis" diagnosis code for the prediction of esophagitis. Secondary analyses determined the performance characteristics of the diagnostic codes for esophageal ulcer, esophageal stricture, gastroesophageal reflux disease (GERD), gastritis, gastric ulcer, and duodenal ulcer.
Results: The authors linked 500 patient records to electronic discharge abstracts. When listed as the most responsible diagnosis for admission, the ICD-9 codes for esophagitis showed a sensitivity of 46.79%, a specificity of 98.83%, and a PPV of 94.81%. When listed as a secondary diagnosis, the ICD-9 codes showed a sensitivity of 70.51%, a specificity of 97.67%, and a PPV of 93.22%. The diagnostic properties of ICD-9 codes for GERD (most responsible, secondary) were as follows: sensitivity (56.10%, 78.66%), specificity (98.51%, 96.73%), and PPV (94.84%, 92.14%).
Conclusions: The ICD-9 diagnosis codes for benign upper gastrointestinal diseases are highly specific and associated with strong PPVs, but have poor sensitivity.