Usefulness of the stool Wright's stain in the emergency department

A prospective study was conducted to determine if a Wright's stain of stool specimen to detect fecal leukocytes was accurate in predicting the presence of a bacterial pathogen on stool culture. Entry criteria were patient age greater than or equal to 3 months and diarrhea of greater than 1 day. The patient population was drawn from an urban county hospital emergency department on the Texas-Mexican border. A total of 69 patients were evaluated by both routine stool culture and stool Wright's stain. Twenty-three were evaluated for parasitic pathogens. There were seventeen cultures positive for bacterial pathogens and twenty-three positive Wright's stains. Bacterial isolates included Shigella, Salmonella and Campylobacter. Also detected were Giardia, Shistosoma, Blastocytis and Cryptosporidium. The sensitivity of a Wright's stain positive for fecal leukocytes for the presence of a bacterial pathogen by culture was 82%, with a specificity of 83%. These were significantly correlated with a positive culture for a bacterial pathogen (P less than .01). The predictive value of a positive result was 61%, and predictive value of a negative result was 94%, for bacterial pathogens. The Wright's stain is a useful tool for the early presumptive diagnosis of infectious bacterial diarrhea in the emergency department.