General

Core Lab Study

Synonym/Acronym:
stool examination.

Rationale
To assess for indication of disease in the gastrointestinal (GI) tract evidenced in stool samples (e.g., presence of blood, white blood cells [WBCs], ova and parasites, rotavirus antigen, or Clostridioides difficile toxin) toward diagnosing GI bleeding, cancer, inflammation, and infection.

This Core Lab Study is a group of noninvasive microscopic and macroscopic tests; the studies may be requested separately or as a group and are performed to investigate a variety of diseases and disorders of the GI tract. The occult blood (FOB) test is performed as part of a routine fecal analysis. FOB is often ordered individually and is used to screen for colorectal cancer. FOB tests for colon cancer can be performed at home.

Patient Preparation
There are no fluid or activity restrictions unless by medical direction. Instruct the patient to follow a normal diet unless instructed otherwise. If the test is being performed to identify blood, instruct the patient to follow a special diet that includes small amounts of chicken, turkey, and tuna (no red meats); raw and cooked vegetables and fruits; and bran cereal for several days before the test. Foods to avoid with the special diet include beets, turnips, cauliflower, broccoli, bananas, parsnips, and cantaloupe, because these foods can interfere with the occult blood test. Instruct the patient not to use laxatives, enemas, or suppositories for 3 days before the test. As appropriate, consult the testing laboratory regarding pretest instructions; provide the required stool collection container and specimen collection instructions.

Normal Findings
Method: Macroscopic examination, for appearance and color; microscopic examination for presence of parasites, larvae, or eggs, for cell count, and for presence of meat fibers; leukocyte esterase for leukocytes; Benedict solution (copper sulfate) for reducing substances; guaiac for occult blood; x-ray paper for trypsin; enzyme immunoassay (EIA) for rotavirus antigen; immunoassay or molecular methods for Clostridioides glutamate dehydrogenase (GDH), toxin A or toxin B. Note: Multiplex molecular stool tests are available in some laboratories that can simultaneously test for a variety of pathogens (bacterial, viral, and parasitic); Stool sample: Chemiluminescent immunoassay for calprotectin; Immunochemical for Fecal Immunochemical Test (FIT); Multitargeted stool DNA (mt-sDNA or stool DNA [Cologuard]).

Critical Findings and Potential Interventions
N/A