Introduction: Acute overt lower gastrointestinal tract bleeding most commonly presents as hematochezia. Hematochezia has been traditionally defined as bright red blood or maroon stool per rectum. With increasing use of administrative databases in medical research, it has become increasingly important to accurately identify patients with their diagnostic codes. We attempt to define the accuracy of ICD-9-CM (International Classification of Diseases, 9th revision, clinical modification) codes in identifying patients with hematochezia.
Methods: As part of another study we identified all patients discharged with one or more of these ICD-9-CM codes- 569.3 (Hemorrhage of Rectum and Anus), 578.1 (Blood in Stool), 578.9 (Hemorrhage of Gastrointestinal Tract, unspecified) or 562.12 (Diverticulosis of Colon with hemorrhage) from a community hospital in United States over 2 years. A total of 836 charts were identified and their histories reviewed for presence of hematochezia or other signs or symptoms of GI bleed. Stata 13.0 was used for statistical analysis.
Results: Of the 836 identified patients, 69.2% (579) had acute overt GI bleeding (hematochezia, melena or hematemesis), and only 41% (343) had hematochezia. 70% and 92% of patients with codes 569.3 and 562.12 respectively, in as either primary or secondary diagnoses, were found to have hematochezia. In contrast, only 17% with code 578.1(Blood in stool) and 21.1% with 578.9 had hematochezia. 77.8% patients with hematochezia were accounted for by the combined two codes 562.12 and 569.3. The sensitivity and specificity of diagnostic codes in identifying hematochezia are shown Figure 1. Various diagnoses found on chart review of patients with these codes are listed in Table 1. The sensitivity of individual ICD-9-CM codes 562.12 and 569.3 is very low (38% and 31% respectively) although the specificity is very good (97% and 91% respectively). The sensitivity increases considerably to 69% with only a minor loss in specificity to 89% when the presence of either code is used to identify hematochezia. The seemingly relatively specific code 578.1 (blood in stool) is neither specific nor sensitive by itself for detecting hematochezia.
Conclusion: Individual ICD-9-CM codes although specific, are not adequately sensitive in identifying acute overt lower GI bleeding. Multiple codes are necessary to reach marginal sensitivity. Careful chart review is required to accurately identify subjects when using ICD-9-CM (and likely ICD-10) codes for retrospective research.