Synonym
Tubes
Stool (feces) specimen
- Clean leak proof container (provided by lab)
OR - Container with preservative [polyvinyl alcohol (PVA) fixative]
- Submit 5 g (2 ml) of stool
- Rectal swab (if stool collection not possible)
Additional information
- Stool collection:
- Clear instructions should be communicated and given in writing to the patient to ensure proper collection
- Instruct the patient to defecate in a large-mouthed plastic container, bag, or clean bedpan
- If the patient has diarrhea, a large plastic bag attached by adhesive tape to the toilet seat may be used
- Wear gloves, collect the entire stool specimen and transfer it to a container using a clean tongue blade or similar object
- Provide for and respect the person's privacy
- Rectal swab collection:
- The swab is inserted beyond anal sphincter, rotated gently, and withdrawn
- The swab is placed in a clean dry culture container
- Swabbing of lesions of rectal wall or sigmoid colon during proctoscopy or sigmoidoscopy is preferred
- Stool can be collected from the diaper of an infant or incontinent adult. Samples can be collected from temporary ostomy bags
- Empty bladder completely to avoid contamination with urine
- Avoid contamination of water or other body secretions such as menstrual blood
- Do not use laxative, barium sulfate, mineral oil, bismuth, antidiarrheal therapy or antiparasitic therapy2 wks before test
- Label the samples properly including date and time of the collection of stool
- Record recent dietary and travel history if patient has diarrhea
- Send the specimen to lab immediately and do not refrigerate
- 3 separate random stool specimens collected every other day may be necessary
Info
- Stool WBCs test is performed to detect the presence of leukocytes in the stool (feces)
- Leukocytes are not present in stools in a healthy person, but may be present in response to infection or inflammation of the gastrointestinal tract
- Fecal leukocytes can be detected primarily by 2 methods:
- Microscopic analysis of feces (direct smear and stain)
- Chemical analysis by fecal lactoferrin assay
Clinical
- The clinical utility of the test for fecal leukocytes include:
- To assist in the evaluation of the cause of diarrhea
- To assist the clinician in determination of likelihood of bacterial cause of the condition (versus viral, bacterial toxin or parasitic cause)
- Detection of fecal leukocytes has a high sensitivity of 85% and specificity of 88%, especially for bacterial diarrhea, such as Shigella, Salmonella, and Campylobacter, with a positive predictive value of 59% and negative predicative value of 97%
- Fecal leukocytes are detectable in 30-50% cases of antibiotic-associated pseudomembranous colitis
- Cytotoxigenic Clostridium difficile and Entamoeba histolytica may destroy the morphology of fecal leukocytes making the test interpretation difficult by microscopic analysis, but not affecting the lactoferrin assay
- Conditions affecting the intestinal wall such as ulcerative colitis, and invasive bacterial pathogen infections, typically have >3 neutrophils/hpf in the feces
Additional information
- Fecal sample is mixed with methylene blue stain solution (reticulocyte stain) or Wright stain and examined for the presence of leukocytes under microscope
- A glycoprotein component of neutrophillic granules called lactoferrin is released from the fecal leukocytes, which is detectable by rapid latex agglutination method
- The advantages of fecal lactoferrin test includes:
- Sensitivity and specificity is better than microscopic detection of fecal WBCs
- Detects fecal leukocytes even if lysis of WBCs has occurred
- Factors interfering with the test results, include:
- Persons receiving laxative, barium sulfate, mineral oil, bismuth, antidiarrheal therapy or antiparasitic therapywithin the past 2 wks of test
- Bismuth found in paper towels and toilet tissue
- Factors that interfere with proper sample procurement such as:
- Bathroom accessibility
- Home and work environments
- Lifestyle
- Personal habits
- Travel
- Neonates fed with breast milk interferes with fecal lactoferrin test results (false positive)
- Improper collection technique or collection of specimen with formalin preservative
- Exposure of specimen to excessive heat or cold
- Any radiographic contrast media given to patient within 5-10 days before specimen collection
- Stool specimen contaminated with urine, water, or menstrual blood
- Stool collected from toilet bowl
- Related laboratory tests includ
Nl Result
- Microscopic examination: Negative for leukocytes/WBCs
- Fecal lactoferrin: Negative
High Result
Conditions associated with positive fecal leukocytes (primarily neutrophils) include:
- Amebiasis (few)
- Antibiotic-associated pseudomembranous colitis
- Bacillary dysentery
- Campylobacter jejuni infection
- Chronic ulcerative colitis
- Cytotoxic Clostridium difficile infection
- Entamoeba histolytica
- Fistulas of the sigmoid rectum or anus
- Invasive Escherichia coli diarrhea
- Localized GI tract abscesses
- Mycobacterium tuberculosis
- Salmonellosis
- Shigellosis
- Yersinia infection
Typhoid(Salmonella typhi) primarily evokes a mononuclear leukocyte response
Low Result
Conditions associated with absence of leukocytes include:
- Amebic colitis (many RBCs)
- Cryptosporidium
- Noninvasive E. coli diarrhea (Toxin-producing)
- Nonspecific diarrhea such as drug or food induced
- Parasites such as Giardia lamblia, Entamoeba histolytica
- Toxigenic bacteria such as Staphylococcus aureus, Clostridium perfringens, Bacillus cereus
- Vibrio cholerae infection
- Viral diarrhea due to Rotavirus, Norwalk virus etc.
References
- Aly SM et al. The utility of lactoferrin in differentiating parasitic from bacterial infections. J Egypt Soc Parasitol. 2005 Dec;35(3 Suppl):1149-62.
- ARUP Laboratories®. Lactoferrin, Fecal. [Homepage on the internet]©2007. Last accessed on April 4, 2007. Available at URL: http://www.aruplab.com/guides/ug/tests/0061164.jsp
- Cigna Health Corporation®. Fecal Lactoferrin. [Homepage on the internet]©2006. Lastreviewed on October 15, 2006. Last accessed on April 4, 2007. Available at URL: http://www.cigna.com/customer_care/healthcare_professional/coverage_positions/medical/mm_0414_coveragepositioncriteria_lactoferrin_test.pdf
- D’Inca R et al. Calprotectin and lactoferrin in the assessment of intestinal inflammation and organic disease. Int J Colorectal Dis. 2007 Apr;22(4):429-37. Epub 2006 Jul 13.
- eMedicine from WebMD®. Diarrhea. [Homepage on the Internet] ©1996-2006. Last updated on September 28, 2006. Last accessed on April 4, 2007. Available at URL: http://www.emedicine.com/ped/topic583.htm
- Khan AI et al. Analysis of fecal leukocytes and erythrocytes in Shigella infections in urban Bangladesh. Southeast Asian J Trop Med Public Health. 2006 Jul;37(4):747-54.
- Laboratory Corporation of America. White Blood Cells (WBC), Stool. [Homepage on the internet]©2007. Last accessed on April 4, 2007. Available at URL: http://www.labcorp.com/datasets/labcorp/html/chapter/mono/mb008200.htm
- Reddymasu S et al. Is Fecal Leukocyte Test a good predictor of Clostridium difficile associated diarrhea? Ann Clin Microbiol Antimicrob. 2006 Apr 19;5:9.