Intestinal yeast colonization is estimated from rectal swabs, fecal samples, mucosal samples, or duodenal samples (from the area connecting the stomach and small intestine). Clinical scoring systems, such as the Candida score and Candida index, estimate the risk of developing systemic fungal infections in critically ill patients, and include the extent of Candida colonization at multiple body sites in conjunction with other factors (e.g., length of hospital stay, prior use of antibiotics, prior surgery, and illness severity).
An average fecal sample is expected to contain less than 10^4 colony-forming units (CFU) per milliliter (mL), but there is no consensus on the correct threshold for IC diagnosis.[1][2] Studies generally classify a concentration of 10^3 to 10^5 CFU/mL as IC.