Reagents for Diagnostics:
cGMP ¹³C Urea and More

There are a variety of diagnostics that require stable isotope-labeled reagents. Since these reagents are not radioactive, they are used widely because they are safe in patients and provide reliable results to clinicians.

The most common clinical use of stable isotope labeled reagents is in breath tests. These tests typically measure the labeled CO₂ in a patient’s breath after intake of a labeled substrate and assess Helicobacter pylori (H. pylori), liver function, gastric emptying, or fat digestion.

Other types of tests that use stable isotopes in a diagnostic setting include mass spectrometry (MS)-based assays, metabolic flux and kinetic studies, and endocrine/nutritional testing. The MS-based assays are used to measure of hormones, vitamins, drugs, and metabolites. and detect inborn errors of metabolism in newborn screening. For more metabolism-based testing, stable isotopes are used in combination with MS or imaging techniques to measure glucose production, protein turnover, hormone production, energy expenditure, and other metabolic changes.

Benefits of Stable Isotope-Labeled Diagnostic Reagents

Using stable isotope labeled reagents, such as ¹³C urea, in diagnostics has a wide range of benefits given the physio and chemical properties of the carbon-13 isotope. Reagents that are labeled with ¹³C behave chemically similar to their unlabeled counterparts, so do not typically present biological concerns or bias.

Another important benefit of using carbon-13 is that it is a stable isotope of carbon, thus eliminating the challenges of radioactivity in a diagnostic. As compared to the urea breath test (UBT) that uses radioactive carbon-14 (¹⁴C), the ¹³C UBT is not subject to the limitations of ¹⁴C UBT caused by radiation exposure. The ¹³C UBT has been demonstrated to be safe for use with children, pregnant women, and repeat patients, thus broadening patient care.

In summary:

• ¹³C is not radioactive and avoids patient exposure to radiation and challenges associated with using ¹⁴C or other radioactive materials
• Stable isotope-labeled reagents are chemically similar to their unlabeled counterparts, thus having limited to no biological impact on the patient
• Stable isotopes can be detected by known analytical techniques, such as infrared spectroscopy (IR), mass spectrometry (MS), and nuclear magnetic resonance (NMR)
• The ¹³C UBT is a noninvasive, highly sensitive test used to detect H. pylori and other clinical targets that is safe and effective.

What Is H. pylori and Why Is it Important to Diagnose?

H. pylori is a gram-negative bacterium that is spiral-shaped, microaerophilic, and flagellated that infects roughly half of the global population. Infection can result in chronic gastritis and gastroduodenal ulcer disease (peptic ulcers). Its presence has also been shown related to the onset of gastric cancer, hence the criticality of accurate diagnosis and treatment.

There are a variety of methods used to diagnose H. pylori infection, some considered direct and some indirect. The direct methods are characterized as invasive and utilize endoscopy, whereas the indirect methods are noninvasive, using simple breath tests.

Urea Breath Test (UBT): Noninvasive Detection of H. pylori Infection

The UBT uses labeled urea to detect H. pylori, a bacterium linked to gastritis and peptic ulcers. Affecting over half the global population, H. pylori infection is diagnosed reliably via UBT, a simple, patient-friendly test that measures exhaled ¹³C carbon dioxide after ingestion of ¹³C urea.

The ¹³C UBT is considered the gold standard noninvasive test in many settings, with sensitivity and specificity of >95% when performed correctly. It enables the direct functional detection of metabolically active H. pylori infection in patients, which helps to quickly determine the need for treatment or the response to treatment.

The process is simple overall. To begin, a patient breathes into a collection bag or tube for the clinician to measure baseline carbon dioxide (CO₂) levels. Then, a drink containing ¹³C-labeled urea is consumed by the patient and after 15-30 minutes, they breathe again into another collection device. The clinician takes this measurement, which contains ¹³C-labeled CO₂. This is compared to the baseline measurement and, if there is a significant increase in ¹³C CO₂, the result is positive for H. pylori. If there is no increase, the result is negative.

The concept works because H. pylori produces an enzyme called urease, which is an enzyme that breaks down urea into CO₂ and ammonia. Humans do not typically produce urease in the gut this way, so the increase of ¹³C CO₂ is a strong signal that H. pylori is present.

UBT: Comparison to Other Diagnostics

Other diagnostic techniques can be used instead of the ¹³C UBT; however, these are inferior in many cases due to varying factors. The most comparable test is the carbon-14 (¹⁴C) UBT. This uses ¹⁴C, which is a radioactive form of carbon, and, therefore, exposes the patient to low levels of radiation. It is not suitable for certain patient populations, such as pregnant women and children, and patients that need repeated testing. The accuracy of the ¹³C and ¹⁴C UBTs is comparable, making the ¹³C UBT the preferred method since it is much safer.

In many cases, an endoscopy is ordered by the doctor to diagnose H. pylori. This procedure typically involves sedation of the patient to allow for a scope to be inserted through the mouth down to the upper GI, where biopsies are taken.  The obvious advantages of the ¹³C UBT as compared to an endoscopy are to the patient (no physical discomfort–no sedation, more comfortable, easier to administer), but also to the clinician from a diagnostic standpoint. The ¹³C UBT assesses the full stomach, not just those parts biopsied in an endoscopy which could be missed, resulting in a false negative.

Another diagnostic for H. pylori is a serology test that detects IgG antibodies in the blood or in the stool. This test does not distinguish between active and past infection, making it difficult to both diagnose and to determine if a treatment is working, whereas the ¹³C UBT only turns positive with active bacteria. This allows for clear determination if the bacteria have been eradicated by treatment. The ¹³C UBT collection method is also more patient-friendly when it comes to sample acquisition.

How CIL Supports UBT with cGMP ¹³C Urea

CIL manufactures and supplies high-quality, cGMP ¹³C urea, the critical reagent for UBT, to hospitals and laboratories worldwide. CIL began producing cGMP ¹³C urea in the early 1990s and has been producing it ever since. The equates to decades of experience and growth to support this key product.

In response to rising global demand, CIL is actively expanding production capacity of both carbon-13 as a raw material and ¹³C urea to ensure consistent supply and regulatory compliance for diagnostic needs worldwide.

• Global team covering technical, quality, and commercial support
• cGMP-grade reagents trusted by leading clinical laboratories
• Scalable production to meet growing diagnostic market demands
• Multi-site production capabilities
• Comprehensive regulatory and quality assurance oversight

Explore CIL’s Broader Diagnostic Reagent Portfolio

Beyond ¹³C urea for the UBT, CIL offers a wide range of stable isotope-labeled compounds and reagents to support biomarker research, clinical translation, and diagnostic testing. Partner with us for a reliable supply of specialty materials that drive precision medicine and clinical innovation.

References

Wei, B.-R.; Zhao, Y.-J.; Cheng, Y.-F.; et al. 2024. Helicobacter pylori infection and Parkinson’s disease: etiology, pathogenesis and levodopa bioavailability. Immun Ageing, 21(1), 1-13. PMID: 38166953
Best, L.M.; Takwoingi, Y.; Siddique, S.; et al. 2018. Non-invasive diagnostic tests for Helicobacter pylori infection. Cochrane Database Syst Rev, 3(3), CD012080. PMID: 29543326
Ferwana, M.; Abdulmajeed, I.; Alhajiahmed, A.; et al. 2015. Accuracy of urea breath test in Helicobacter pylori infection: Meta-analysis. World J Gastroenterol, 21(4), 1305-1314. PMID: 25632206
Gisbert, J.P.; Pajares, J.M. 2014. ¹³C-urea breath test in the diagnosis of Helicobacter pylori infection – A critical review. Aliment Pharmacol Ther,  20(10), 1001-1017. PMID: 15569102
Savarino, V.; Vigneri, S.; Celle, G. 1999. The ¹³C urea beath test in the diagnosis of Helicobacter pylori infection. Gut, 45 Suppl 1(Suppl 1), I18-22.  PMID: 1045703
Leal, Y.A.; Flores, L.L.; Fuentes-Panan, E.M.; et al. 2011. ¹³C-urea breath test for the diagnosis of Helicobacter pylori infection in children: a systematic review and meta-analysis. Helicobacter, 16(4), 327-337. PMID: 21762274 Gisbert, J.P.; Pajares, J.M. 2004. Review article: ¹³C-urea breath test in the diagnosis of Helicobacter pylori infection – a critical review. Aliment Pharmacol Ther, 20(10), 1001-1017. PMID: 15569102