Accuracy of ICD-9 codes in identifying patients with peptic ulcer and gastrointestinal hemorrhage in the regional healthcare administrative database of Umbria

BACKGROUND: Peptic ulcer is a widespread disease, frequently complicated by perforation and bleeding. Administrative databases are useful tool to perform epidemiological and drug utilization studies, but they need a validation process based on a comparison with the original data contained in the medical charts. Our aim was to evaluate the accuracy of the ICD-9 codes in identifying patients with peptic ulcer and gastrointestinal hemorrhage in the regional administrative database of Umbria. METHODS: The index test of our study was the hospital discharge abstract database of the Umbria region (Italy), while the reference standard was the clinical information collected in the medical charts. The study population were adult patients with a hospital discharge for peptic ulcer or gastrointestinal hemorrhage in the period 2012–2014. A random sample of cases and non-cases was selected and the corresponding medical charts were reviewed. Cases of peptic ulcer were confirmed based on endoscopy, radiology, and surgery, while adjudication of gastrointestinal hemorrhage was based on presence of hematemesis, melena, and rectal bleeding. RESULTS: Overall, we reviewed 445 clinical charts of cases and 80 clinical charts of non-cases. The diagnostic accuracy results were: code 531 (gastric ulcer), sensitivity and NPV 98%, specificity 88%, and PPV 91%; code 532 (duodenal ulcer), sensitivity and NPV 100%, specificity and PPV 98%; code 534 (gastrojejunal ulcer), sensitivity and NPV 100%, specificity 70%, and PPV 45%; code 578 (gastrointestinal hemorrhage), sensitivity 96%, specificity 90%, PPV and NPV 94%. CONCLUSIONS: Our results showed a high level of diagnostic accuracy for most of the codes considered. The ICD-9 code 534 of gastrojejunal ulcer had a lower level of specificity and PPV due to false positives, being mainly misclassifications for coding errors. These validated codes can be used for future epidemiological studies and for health services research.