OCCULT BLOOD VERSUS FECAL LEUKOCYTES IN THE DIAGNOSIS OF BACTERIAL DIARRHEA - A STUDY OF US TRAVELERS TO MEXICO AND MEXICAN CHILDREN

A study was done to test the effectiveness of fecal occult blood as a screening test for invasive bacterial pathogens and as a substitute fo r the fecal leukocyte examination in adult and pediatric cases of acut e diarrhea. United States citizens studying in Mexico and Mexican chil dren, both with acute diarrhea had their stools cultured, examined for fecal leukocytes, and tested for occult blood. Using culture results as the criterion standard for detection of bacterial agents, and fecal leukocytes for diarrhea associated with diffuse colonic inflammation, occult blood was tested for its sensitivity, specificity, and predict ive value using 2 x 2 tables. Analysis of the data found that occult b lood negative samples were reliable indicators of a lack of invasive b acteria in both adult and pediatric patients (negative predictive valu es of 87% and 96%, respectively). Positive results for either test wer e not reliably predictive as indicators of invasive bacteria among adu lts. A positive occult blood test result was significantly more sensit ive than a positive fecal leukocyte test result (79% versus 42%) in de tecting invasive bacteria in the pediatric patients; however, the posi tive predictive value was only 24%. The fecal occult blood test is an uncomplicated, low-cost test that was reliable when giving a negative result in detecting a lack of invasive bacteria in adult and pediatric patients with diarrhea. Ln children, a positive result on a fecal occ ult blood test is sensitive but not specific in detecting invasive bac terial enteropathogens. These data also indicate that a commercially a vailable test for occult blood represents a suitable alternative to mi croscopic examination of fecal samples for leukocytes obtained from pa tients with acute diarrhea.