Society of Nuclear Medicine Procedure Guideline for C-14 Urea Breath Test version 3.0, approved June 23, 2001 Authors: Helena R. Balon, MD (William Beaumont Hospital, Royal Oak, MI); Eileen Roff, RN, MSA, (William Beaumont Hospital, Royal Oak, MI); John E. Freitas, MD (St. Joseph Mercy Hospital, Ann Arbor, MI); Vanessa Gates, MS (William Beaumont Hospital, Royal Oak, MI); and Howard J. Dworkin, MD (William Beaumont Hospital, Royal Oak, MI). I. Purpose istration of C-14 urea, followed by sampling of the ex- haled breath at timed intervals. The breath samples The purpose of this guideline is to assist nuclear are then analyzed in a liquid scintillation counter. medicine practitioners in recommending, perform- ing, interpreting and reporting the results of the C- 14 urea breath test. III. Common Indications Detection of the presence of H. pylori in the stomach. II. Background Information and Definitions A. Given the very high probability of patients with duodenal ulcers being infected with H. pylori, the The discovery of the Gram-negative spiral rod, Heli- C-14 urea breath test has not been routinely cobacter pylori, in the 1980s radically changed the ap- recommended for initial diagnosis, but has proach to treatment of peptic ulcer disease (PUD). been recommended to document H. pylori erad- The causal relationship between H. pylori infection ication following anti-H. pylori therapy. Eradi- and chronic gastritis is well established. Although cation should be confirmed no sooner than 1 only a small fraction of H. pylori-positive patients de- month, and preferably longer, after completion velop PUD, essentially all patients with duodenal ul- cers and about 80% of patients with other than non- of therapy. steroidal anti-inflammatory drug (NSAID)-induced B. Since the prevalence of H. pylori in gastric ulcer gastric ulcers are infected with H. pylori. Eradication patients (non-NSAID-induced gastric ulcers) is of H. pylori markedly reduces ulcer recurrence to about 80%, the C-14 urea breath test may be used <10% in 1 yr vs. 60-100% recurrence rate in 1 yr with for initial diagnosis as well as follow-up in this conventional anti-ulcer therapy. patient subset. There is also evidence that H. pylori infection is as- sociated with adenocarcinoma and lymphoma of the IV. Procedure stomach, although in the United States fewer than 1% of H. pylori-infected people will develop gastric cancer. A. Patient Preparation Further research is needed to determine the role of 1. Patients should be off the following medica- H. pylori eradication in gastric cancer prevention. tions: The presence of active H. pylori infection can be di- a. Antibiotics and bismuth compounds for 30 agnosed non-invasively with the C-14 urea breath days before the test. test. This test is based on the detection of the enzyme b. Sucralfate and proton pump inhibitors urease produced by H. pylori. Since urease is not pre- (e.g., omeprazole, esomeprazole, lansopra- sent in normal human tissues, and since other ure- zole, rabeprazole, pantoprazole) for 2 wk ase-producing bacteria do not colonize the stomach, before the test. the presence of urease in the stomach can be equated 2. Patients should be NPO for at least 6 hr before with H. pylori infection. the test. In the presence of urease, orally administered C- B. Information Pertinent to Performing the Procedure 14 urea will be hydrolyzed into ammonia and A relevant history should be obtained; particu- 14 CO2. 14CO2 is absorbed into the circulation and ex- larly, a list of relevant medications and the time haled by the lungs. The presence of a significant of their most recent administration should be amount of 14CO2 in the exhaled breath indicates ac- available. tive H. pylori infection. C. Precautions The C-14 urea breath test consists of the oral admin- None 38 • C-14 UREA BREATH TEST Radiation Dosimetry for C-14 Urea* Patient Administered Activity Organ Receiving the Effective Dose KBq Largest Radiation Dose Equivalent+ (µCi) mGy/MBq mSv/MBq (rad/mCi) (rem/mCi) HP-positive female 37 p.o. 0.14 0.08 urinary bladder wall (1) (0.52) (0.30) HP-negative female 37 p.o. 0.19 0.049 urinary bladder wall (1) (0.70) (0.18) HP-positive male 37 p.o. 0.10 0.062 urinary bladder wall (1) (0.37) (0.23) HP-negative male 37 p.o. 0.14 (0.038) urinary bladder wall (1) (0.52) (0.14) *from Stubbs JB, Marshall BJ. Radiation dose estimates for the C-14 labeled urea breath test. J Nucl Med 1993; 34:821-825 D. Radiopharmaceutical tion fluid (e.g., BCSTM, Econo-SafeTM) is C-14 urea in a capsule form containing 1 mg urea added to each vial immediately after labeled with 37 kBq (1 µCi) C-14. This prepara- breath collection and mixed thoroughly. tion is currently available as PYTest TM from b. A C-14 standard should be prepared by Kimberly-Clark/Ballard Medical Products. adding a known volume (e.g., 50 ml) of a C-14 is a pure beta-emitter with a physical half calibrated C-14 reference standard (the life of 5730 yr and maximum energy of 160 keV. known activity is stated on the vial) to a To measure beta emissions, C-14 is counted in a blank breath sample (a breath sample con- liquid scintillation counter. taining no C-14). The same volume of scin- E. Procedure tillation fluid that is used for patient sam- 1. Breath sample collection ples is added to this standard. At time zero, the patient swallows the capsule c. A blank (background) sample should be containing 37 kBq (1 µCi) C-14 urea with 20 prepared using an identically treated ml lukewarm water. At 3 min post-dose, the breath sample from a person not receiving patient drinks another 20 ml lukewarm water. C-14 urea. At 10 min post-dose, the patient is asked to d. All timed breath samples, the blank sample take a deep breath, hold it for approximately and the C-14 standard are counted for 5–20 5–10 sec and then exhale through a straw into min in a liquid scintillation counter (LSC), a mylar balloon. Another optional breath using a C-14 window. sample (into another balloon) can be obtained e. Calculations at 15 min post-dose. Raw sample counts per minute (cpm) 2. On site breath sample analysis should be background-corrected and con- a. For each balloon, 2.5 ml trapping solution is verted into disintegrations per minute pipetted into a scintillation vial. The trap- (dpm) using the following formula: ping solution (collection fluid) is available from the manufacturer and contains 1 DPM = (sample cpm – blank cpm) mmol hyamine, methanol and thymolph- Efficiency (eq. 1) thalein. The air from the balloons is trans- LSC Efficiency ferred into the scintillation vials using an The C-l4 standard (see section E.2.b.) air pump and plastic tubing. The color should be counted with every set of pa- change of the collection fluid (from blue to tient samples. The efficiency of the colorless) indicates the end point of trans- counter for the specific procedure and the fer. At this point 1 mmol CO2 has been specific scintillation cocktail can then be trapped. Ten milliliters of suitable scintilla- determined as: SOCIETY OF NUCLEAR MEDICINE PROCEDURE GUIDELINES MANUAL JUNE 2002 • 39 Efficiency = (standard cpm – blank cpm) or even 20 min post-dose may be helpful) standard dpm (eq. 2) 2. Causes of potential false-positive results: a. Resective gastric surgery with potential re- 3. Off site analysis sultant bacterial overgrowth (non- H. pylori Balloons with breath samples can also be urease). shipped to another institution/laboratory, if b. Achlorhydria a liquid scintillation counter is not available 3. Chemiluminescence on site. If a value of 50–300 dpm is obtained immedi- F. Interventions ately after the addition of the scintillation None fluid, the sample should be recounted in 1–2 G. Processing hr or the next day, to exclude falsely elevated None counts due to chemiluminescence. H. Interpretation Criteria Reference values recommended by the manufac- V. Issues Requiring Further Clarification turer are as follows: None < 50 dpm at 10 min Negative for H. pylori 50-199 dpm at 10 min Indeterminate for H. pylori ≥ 200 dpm at 10 min Positive for H. pylori VI. Concise Bibliography Friedman LS. Helicobacter pylori and nonulcer dyspep- I. Reporting sia (editorial). New Engl J Med. 1998;339: 1928–1930. Aside from patient demographics, the report NIH Consensus Statement. Helicobacter pylori in peptic should include the following information: ulcer disease. JAMA. 1994;272:65–69. 1. Indication for the study (e.g., suspected H. py- PYTestTM package insert. Ballard Medical Products, lori infection, follow-up after anti-H. pylori Draper, Utah; August 1997. therapy, etc.) Soll AH. Consensus Statement. Medical treatment of 2. Procedure (i.e., radiopharmaceutical and peptic ulcer disease - practice guidelines. JAMA. dosage, number and timing of breath samples 1996;275:622–629. collected) Stubbs JB, Marshall BJ. Radiation dose estimates for the 3. Result (i.e., net dpm in the 10 min sample) C-14 labeled urea breath test. J Nucl Med. 4. Reference ranges (normal values) 1993;34:821–825. 5. Study limitations, confounding factors 6. Interpretation (i.e., positive, negative, indeter- VIII. Disclaimer minate for the presence of active H. pylori in- fection) The Society of Nuclear Medicine has written and J. Quality Control (QC) approved guidelines to promote the cost-effective Liquid scintillation counter (LSC) use of high quality nuclear medicine procedures. Proper calibration and QC of the LSC should These generic recommendations cannot be applied be performed as per facility procedure. to all patients in all practice settings. The guidelines K. Sources of Error should not be deemed inclusive of all proper proce- 1. Causes of potential false-negative results: dures or exclusive of other procedures reasonably a. Antibiotics (if administered within 30 days directed to obtaining the same results. The spec- of the test) trum of patients seen in a specialized practice set- b. Bismuth (if administered within 30 days of ting may be quite different than the spectrum of pa- the test) tients seen in a more general practice setting. The c. Sucralfate (if administered within 14 days appropriateness of a procedure will depend in of the test) part on the prevalence of disease in the patient d. Proton pump inhibitors (see examples in population. In addition, the resources available to section IV.A.b.) if administered within 14 care for patients may vary greatly from one med- days of the test ical facility to another. For these reasons, guide- e. Non-fasting lines cannot be rigidly applied. f. Resective gastric surgery Advances in medicine occur at a rapid rate. The g. Difficulty with swallowing test capsule date of a guideline should always be considered in (additional breath samples collected at 15 determining its current applicability.
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