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

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.