AN OBJECTIVE-MEASURE OF STOOL COLOR FOR DIFFERENTIATING UPPER FROM LOWER GASTROINTESTINAL-BLEEDING

Subjective reporting of the color of blood passed per rectum has been used to predict the location of gastrointestinal bleeding, but the val idity of this clinical approach has never been evaluated systematicall y. In this study we determined the spectrum of patient and physician d escriptors used to characterize the color of blood passed per rectum a nd evaluated prospectively if an objective test of stool color would c orrelate with or improve upon subjective descriptions in predicting bl eeding locations. The objective test employed was a card containing fi ve numbered colors that typify the spectrum of stool blood colors. One hundred twenty patients used 23 different descriptors or terms to ver balize the color of blood they passed per rectum, and in 22% of cases there was a seeming discrepancy between their verbalized color and the color they pointed to on the test card. Patients pointing to card col or 4 (the black color) resulted in a closer matching to an upper bleed ing source than physicians using terminology such as melena or tarry s tools. Likewise, patients picking card colors 1 and 2 (the brightest r ed colors) resulted in closer matching to a coloanorectal bleeding sou rce than physicians using the terms hematochezia or bright red blood p er rectum (P < 0.02 for each comparison). The positive predictive valu e of card color 4 for an upper bleeding source was very high both when patients pointed to this color or when it was determined from the ava ilable stool (0.95 and 0.98, respectively). The positive predictive va lue of card color 1 for lower bleeding was greater for patients select ing this color than for a direct stool comparison (1.00 vs 0.83). This study revealed marked variability and surprising inconsistency in sub jective color reporting for both patients and doctors and the superior ity of several card colors for separating upper from lower bleeding so urces. This simple objective test should improve upon terms such as me lena and hematochezia and help direct the initial diagnostic evaluatio n of gastrointestinal bleeding.