Biomedicines. 2025 Feb 17;13(2):491. doi: 10.3390/biomedicines13020491.

Katelin Durham ^1 2, Tyler Atagozli ³, David E Elliott ^1 2, M Nedim Ince ^1 2

Author information

¹Division of Gastroenterology and Hepatology, Department of Internal Medicine, University of Iowa, 200 Hawkins Drive, Iowa City, IA 52242, USA.

²Iowa City Veterans Affairs Medical Center, 601 Highway 6 W, Iowa City, IA 52246, USA.

³Carver College of Medicine, University of Iowa, 375 Newton Road, Iowa City, IA 52242, USA.

Abstract

Inflammatory bowel diseases (IBDs) comprise a group of chronic gastrointestinal disorders characterized by periods of relapse and remission. The mainstay of treatment is medical, involving medications such as steroids, immune modulators, monoclonal antibodies (categorized as biologics), and small molecules. These medications can provide profound therapeutic benefits, but they can also cause severe and irreversible toxicities. Clinicians may utilize laboratory tests in the diagnosis and management of IBD including assessment of disease activity, monitoring medication response or toxicity, surveillance of infectious complications, and detection of nutritional deficiencies. Routine use of laboratory tests may help clinicians avoid reactivation of life-threatening infections such as tuberculosis or hepatitis B virus upon initiation of immune suppressive therapy. They can also be used to detect vitamin deficiencies such as B12 deficiency, which has the potential to cause irreversible neurologic damage. While some laboratory tests constitute established practices, the utility of newer tests such therapeutic drug monitoring (TDM) in the era of biologics is an evolving topic. Although clinical assessment with imaging, endoscopic, and histopathological examination is standard practice, laboratory tests serve as valuable adjuncts. We aim to explore the broad range of laboratory tests available to clinicians and to summarize their application in the current management of IBD in daily clinical practice, with special attention to updates in therapeutic drug monitoring.