Laboratory Testing for IBS Patients

Initial Screening Tests

The American Gastroenterological Association recommends a complete blood count (CBC) to screen for anemia and exclude inflammatory processes in all patients with suspected IBS 2, 1
The American Gastroenterological Association recommends C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) to assess for occult inflammation in all patients with suspected IBS 3, 1
Celiac serology (anti-endomysial antibodies) should be checked in all patients with suspected IBS, as celiac disease may occur more frequently in IBS populations 3, 1
Stool occult blood testing (Hemoccult) is recommended for screening purposes in all patients with suspected IBS 2, 1

For patients under age 45 with diarrhea, fecal calprotectin is recommended to exclude inflammatory bowel disease 1
Lactose breath testing is recommended for patients who regularly consume more than 0.5 pint (280 ml) of milk or equivalent dairy products daily, especially those from ethnic groups with high lactose malabsorption rates 3, 1
Stool examination for ova, cysts, and parasites is recommended based on geographic area and relevant clinical features 2
SeHCAT scanning or serum 7α-hydroxy-4-cholesten-3-one is recommended to exclude bile acid diarrhea in refractory cases 1

Colonoscopy is recommended for patients over age 50 years or those with a positive family history of colorectal cancer, regardless of symptom pattern 2, 1
Serum chemistries and albumin can be ordered based on symptom pattern and clinical features 2

Fever, significant weight loss, or rectal bleeding require comprehensive diagnostic evaluation rather than minimal testing 2
Anemia or abnormal physical findings on examination require comprehensive diagnostic evaluation rather than minimal testing 2
Nocturnal symptoms or acute symptom onset in previously well-controlled disease require comprehensive diagnostic evaluation rather than minimal testing 4
Age over 50 years at symptom onset requires comprehensive diagnostic evaluation rather than minimal testing 3
Family history of inflammatory bowel disease or colorectal cancer requires comprehensive diagnostic evaluation rather than minimal testing 2
Elevated inflammatory markers (CRP, ESR) or fecal calprotectin require comprehensive diagnostic evaluation rather than minimal testing 4