The validity of 13C-urea breath test (13C-UBT) for
In this prospective study,
A total of 1,207 who successfully took
In a country with high prevalence of atrophic gastritis or IM, false positivity remained common despite the use of citric acid in 13C-UBT.
The validity of 13C-urea breath test (13C-UBT) for
In this prospective study,
A total of 1,207 who successfully took
In a country with high prevalence of atrophic gastritis or IM, false positivity remained common despite the use of citric acid in 13C-UBT.
The 13C-urea breath test (13C-UBT) is a noninvasive, simple, and widely available test for the initial diagnosis of
To decrease the rate of false positivity, the use of a citric acid meal has been proposed to increase the 13C-UBT value in
Based on this background, we hypothesized that a citric acid meal could increase the accuracy of 13C-UBT. The aim of this study was to determine the effect of citric acid meal on the diagnostic validity of 13C-UBT after
Patients with proven
For treatment of
Before 13C-UBT, patients were instructed to stop taking medications such as bismuth salts or antibiotics for 4 weeks and PPI for 2 weeks. They were asked to fast for a minimum of 4 hours. Patients were assigned to receive the test meal (citric acid group) for 13C-UBT on Tuesdays or to the control group on Mondays. After washing the oral cavity by gargling, participants in the citric acid group received the citric acid solution (Dongwon, Seoul, Korea; 4 g in 200 mL of water containing 50 g [200 kcal] glucose polymer with artificial sweetener). After consumption of the meal, a predose breath sample was obtained, and then 100 mg tablet of 13C-urea (UBiTkit™; Otsuka Pharmaceutical Co. Ltd., Tokyo, Japan) was administered. In the control group, 13C-UBT was performed with prior consumption of a glucose meal without citric acid. Breath samples were collected in the sitting position using special breath collection bags before 13C-urea administration (baseline) and 20 minutes after administration. Collected breath samples were analyzed using an isotope-selective, nondispersive infrared spectrometer (UbiT-IR 300®; Otsuka Pharmaceutical Co. Ltd). Despite the lack of local validation, the 13C-UBT cutoff value of 2.5‰ was used as recommended by the manufacturer and a delta 13CO2 of ≥2.5‰ was considered positive.
Two biopsy specimens were obtained from the antrum and gastric body for histology. The presence of
Sensitivity, specificity, and likelihood ratios for a positive test result (LRp) for a negative test result (LRn) of 13C-UBT were calculated for the citric acid and control groups. Statistical analysis was conducted using PASW Statistics version 18.0 (SPSS, Chicago, IL, USA). Positive predictive value (PPV) and negative predictive value (NPV) were included in LRs. Student t-test, Pearson chi-square test, and Fisher exact test were used, as appropriate, for univariate analysis of factors affecting the accuracy of 13C-UBT. A logistic regression model was used for multivariate analysis. Statistical significance was considered at p<0.05.
Fig. 1 shows the current study flow. Of 1,207 consecutive participants who underwent 13C-UBT after
A total of 114 participants were evaluated by endoscopic biopsy for histological analysis (modified Giemsa test) of the antrum and gastric body, while 98 participants were evaluated by CLOtest of the antrum and gastric body for determination of
Of 1,207 participants, 36 (3.0%) in the meal group and 48 (3.9%) in the control group had results in the gray area (2.0‰ to 10.0‰) for 13C-UBT (Fig. 1). Fifteen participants in the meal group and 11 participants in the control group were analyzed by endoscopic biopsy methods (histology or rapid urease test). The diagnostic accuracy, sensitivity, specificity, PPV, NPV, LRp, and LRn of 13C-UBT for the meal group in the “gray area” were 53.3% (95% CI, 26.6% to 78.7%), 75.0% (95% CI, 19.4% to 99.4%), 45.5% (95% CI, 16.8% to 76.6%), 33.3% (95% CI, 18.6% to 52.2%), 83.3% (95% CI, 44.8% to 96.9%), 1.38 (95% CI, 0.63 to 3.00), and 0.55 (95% CI, 0.09 to 3.88), respectively. They were 45.5% (95% CI, 16.8% to 76.6%), 100.0% (95% CI, 29.2% to 100.0%), 25.0% (95% CI, 3.2% to 65.1%), 33.3% (95% CI, 25.1% to 42.7%), 100.0%, 1.33 (95% CI, 0.89 to 1.99), and 0.00, respectively, for the control group in the “gray area” (Table 3).
Table 4 shows risk factors that caused mismatched results between 13C-UBT and endoscopic biopsy-based tests. Except sex (p=0.039), there was no significant risk factor based on univariate analysis.
To exclude the influence of gastric mucosal atrophy on the diagnostic accuracy of 13C-UBT, subgroup analysis was performed for the diagnostic validity using 69 patients who were revealed to have no or mild gastric atrophy based on gastric mucosal biopsy (31 subjects in the meal group and 38 subjects in the control group). The diagnostic accuracy was 86.8% (95% CI, 71.9% to 95.6%) for the control group and 80.7% (95% CI, 62.5% to 92.3%) for the meal group (p=0.637). Diagnostic sensitivity, specificity, PPV, NPV, LRp, and LRn were 100.0% (95% CI, 47.8% to 100.0%), 76.9% (95% CI, 56.4% to 91.0%), 45.5% (95% CI, 29.2% to 62.7%), 100.0%, 4.33 (95% CI, 2.15 to 8.74) and 0.0 for the meal group and 100.0% (95% CI, 47.8% to 100.0%), 84.9% (95% CI, 68.1% to 94.9%), 50.0% (95% CI, 30.8% to 69.2%), 100.0%, 6.6 (95% CI, 2.94 to 14.80), and 0.00 for the control group, respectively (
To exclude any influence of gastric mucosal IM on the diagnostic accuracy of 13C-UBT, subgroup analysis was performed for the diagnostic validity using 86 patients who were revealed to have no or mild IM based on gastric mucosal biopsy (48 subjects in the meal group and 38 subjects in the control group). The diagnostic accuracy was 86.8% (95% CI, 71.9% to 95.6%) for the control group and 85.4% (95% CI, 72.2% to 93.9%) for the meal group (p=1.000). Diagnostic sensitivity, specificity, PPV, NPV, LRp, and LRn were 90.0% (95% CI, 55.5% to 99.8%), 84.2% (95% CI, 68.8% to 93.9%), 60.0% (95% CI, 41.2% to 76.3%), 97.0% (95% CI, 83.2% to 99.5%), 5.70 (95% CI, 2.66 to 12.22), and 0.12 (95% CI, 0.02 to 0.77) for the meal group and 80.0% (95% CI, 28.4% to 99.5%), 87.9% (95% CI, 71.8% to 96.6%), 50.0% (95% CI, 26.5% to 73.5%), 97.7% (95% CI, 83.3% to 99.4%), 6.60 (95% CI, 2.38 to 18.26), and 0.23 (95% CI, 0.04 to 1.32) for the control group, respectively (
The use of 4 g of citric acid as a test meal failed to increase the diagnostic validity of 13C-UBT after
Generally, moderate to severe gastric atrophy and IM were associated with increased risk of a mismatched result of 13C-UBT value after
Taken together, these results suggest that in regions of the world where AG is common, the diagnostic accuracy of the test needs to be increased, such as by using citric acid meals and different doses or formulations of urea. The original 13C-UBT employed a test meal designed to slow gastric emptying and maximize the distribution of the substrate within the stomach to increase the area and time of contact between bacteria and the substrate.20 Different doses (1, 2, or 4 g) of citric acid can produce significant increases in breath 13CO2 activity compared to other meals, such as ascorbic acid, subcutaneous pentagastrin, and glucose polymer.9 Citric acid could slow gastric emptying and enhance the intragastric distribution of urea.3 Most studies evaluating the role of citric acid in UBT have shown higher delta values with citric acid in comparison with other pretest meals or no test meals.12,21,22 Similarly, the standard deviation of δ 13C-UBT value in the citric acid group of the present study was significantly higher than that of the control group, while the mean δ 13C-UBT value for positive 13C-UBT results in the citric acid group was significantly higher. Furthermore, the sensitivity was higher in the citric acid meal group. These results reflect the increase in urease activity by citric acid (i.e., increase of δ 13C-UBT value in
In our study, the use of citric acid as a test meal improved the diagnostic sensitivity after
To obtain a statistically significant improvement of diagnostic accuracy from 90% to 95% would likely require an extremely large sample size. However, previous studies could not meet the needed sample size, either, due to limitations in the clinical situation, such as high cost of endoscopy and the invasiveness of endoscopic biopsy-based
Our results are consistent with our previous suggestion that moderate to severe IM is an independent risk factor for a false positivity.4,28 As the degree of gastric atrophy becomes severe, the environment in the stomach changes to a hypochlorhydric state and causes overgrowth of non-
In conclusion, our results show that citric acid did not increase the diagnostic accuracy or specificity of 13C-UBT after
This work was supported by a grant (number: 2011-0030001) of the National Research Foundation (NRF) for the Global Core Research Center (GCRC) funded by the Ministry of Science, ICT and Future Planning (MSIP), Republic of Korea.
The authors greatly appreciate Prof. David Y. Graham for suggesting this research topic and his endless interest and advice.
No potential conflict of interest relevant to this article was reported.
Guarantor of the article: N.K. Study design, data analysis, statistical analysis, data interpretation and manuscript drafting: Y.H.K. Study design, enrolled the subjects, data interpretation, and critical revision: N.K. Enrolled subjects and edited the manuscript: H.Y., C.M.S., Y.S.P., D.H.L. All authors approved the final version of the manuscript.
See editorial on page 479.
13C-UBT, 13C-urea breath test;
13C-UBT, 13C-urea breath test;
Baseline Characteristics of Participants in the Citric Acid Group and Control Group
Characteristic | Meal group (n=562) | Control group (n=645) | p-value* |
---|---|---|---|
Sex, male/female | 280 (49.8)/282 (50.2) | 343 (53.2)/302 (46.8) | 0.134 |
Age, yr | 56.3±12.3 | 55.3±11.8 | 0.783 |
Initial diagnosis | 0.002 | ||
Functional dyspepsia | 125 (22.2) | 143 (22.2) | |
Atrophic gastritis | 302 (53.7) | 339 (52.6) | |
Benign peptic ulcer | 75 (13.3) | 104 (16.1) | |
Gastric dysplasia | 22 (3.9) | 35 (5.4) | |
Early gastric cancer | 30 (5.3) | 11 (1.7) | |
Gastric MALT lymphoma | 5 (0.9) | 13 (2.0) | |
ITP | 3 (0.5) | 0 | |
13C-UBT value, ‰ | 10.3±26.4 | 5.1±12.6 | <0.001 |
13C-UBT positive, % | 116 (20.6) | 139 (21.6) | 0.395 |
Mean 13C-UBT value in positive results, ‰ | 48.3±39.7 | 22.1±19.2 | <0.001 |
Mean 13C-UBT value in negative results, ‰ | 0.4±0.8 | 0.5±0.4 | 0.513 |
No. of |
0.994 | ||
First | 471 (83.8) | 541 (80.9) | |
Second | 61 (10.9) | 69 (13.0) | |
Third | 30 (5.3) | 35 (6.0) | |
Mean time from |
5.3±1.2 | 5.4±2.1 | 0.696 |
Data are presented as number (%) or mean±SD.
MALT, mucosa-associated lymphoid tissue; ITP, idiopathic thrombocytopenic purpura; 13C-UBT, 13C-urea breath test;
Diagnostic Validity of 13C-UBT Compared to Those of Endoscopic Biopsy Methods
13C-UBT value | Using both endoscopic biopsy-based methods for |
|||
---|---|---|---|---|
Positive | Negative | |||
Meal group (n=60) | ≥2.5‰ | 11 | 9 | PPV 55.0% |
<2.5‰ | 1 | 39 | NPV 97.5% | |
Sensitivity 91.7% | Specificity 81.3% | |||
Control group (n=62) | ≥2.5‰ | 10 | 6 | PPV 62.5% |
<2.5‰ | 1 | 45 | NPV 97.8% | |
Sensitivity 90.9% | Specificity 88.2% |
13C-UBT, 13C-urea breath test;
Diagnostic Validity of 13C-UBT Compared to Those of Endoscopic Biopsy Methods in the Gray Zone (Value of 13C-UBT: 2.0‰–10.0‰)
13C-UBT value | Using both endoscopic biopsy-based methods for |
|||
---|---|---|---|---|
Positive | Negative | |||
Citric acid group (n=15) | ≥2.5‰ | 3 | 6 | PPV 33.3% |
<2.5‰ | 1 | 5 | NPV 83.3% | |
Sensitivity 75.0% | Specificity 45.5% | |||
Control group (n=11) | ≥2.5‰ | 3 | 6 | PPV 33.3% |
<2.5‰ | 0 | 2 | NPV 100.0% | |
Sensitivity 100.0% | Specificity 25.0% |
13C-UBT, 13C-urea breath test;
Risk Factors for Mismatched Results between 13C-UBT and Endoscopic Biopsy-Based Methods after
Variable | 13C-UBT result compared with both endoscopic biopsy-based methods | p-value* | |
---|---|---|---|
Matched group (n=105) |
Mismatched group (n=17) |
||
Sex, male/female | 60 (57.1)/45 (42.9) | 5 (29.4)/12 (70.6) | 0.039 |
Use of citric acid | 50 (47.6) | 10 (58.8) | 0.441 |
Age, yr | 56.2±11.3 | 57.0±12.0 | 1.000 |
Diagnosis | 0.623 | ||
Functional dyspepsia | 19 (18.1) | 3 (17.6) | |
Atrophic gastritis | 23 (21.9) | 6 (35.3) | |
Benign peptic ulcer | 22 (21.0) | 1 (5.9) | |
Gastric dysplasia | 13 (12.4) | 1 (5.9) | |
Early gastric cancer | 20 (19.0) | 5 (29.4) | |
Gastric MALT lymphoma | 8 (7.6) | 1 (5.9) | |
Mean time from |
5.6±0.6 | 5.5±0.8 | 0.831 |
Mean time from 13C-UBT to endoscopic biopsy, wk | 31.8±27.6 | 25.2±21.0 | 0.285 |
Gastric mucosal status | |||
Gastric atrophy | 0.961 | ||
Not investigated | 7 (6.7) | 1 (5.9) | |
Not applicable | 23 (21.9) | 3 (17.6) | |
None | 45 (42.9) | 8 (47.1) | |
Mild | 13 (12.4) | 3 (17.6) | |
Moderate | 14 (13.3) | 2 (11.8) | |
Marked | 3 (2.9) | 0 | |
Gastric intestinal metaplasia | 0.862 | ||
Not investigated | 7 (6.7) | 1 (5.9) | |
None | 54 (51.4) | 10 (58.8) | |
Mild | 20 (19.0) | 2 (11.8) | |
Moderate | 17 (16.2) | 2 (11.8) | |
Marked | 7 (6.7) | 2 (11.8) |
Data are presented number (%) or mean±SD.
13C-UBT, 13C-urea breath test; MALT, mucosa-associated lymphoid tissue.
Baseline Characteristics of Participants in the Citric Acid Group and Control Group
Characteristic | Meal group (n=562) | Control group (n=645) | p-value* |
---|---|---|---|
Sex, male/female | 280 (49.8)/282 (50.2) | 343 (53.2)/302 (46.8) | 0.134 |
Age, yr | 56.3±12.3 | 55.3±11.8 | 0.783 |
Initial diagnosis | 0.002 | ||
Functional dyspepsia | 125 (22.2) | 143 (22.2) | |
Atrophic gastritis | 302 (53.7) | 339 (52.6) | |
Benign peptic ulcer | 75 (13.3) | 104 (16.1) | |
Gastric dysplasia | 22 (3.9) | 35 (5.4) | |
Early gastric cancer | 30 (5.3) | 11 (1.7) | |
Gastric MALT lymphoma | 5 (0.9) | 13 (2.0) | |
ITP | 3 (0.5) | 0 | |
13C-UBT value, ‰ | 10.3±26.4 | 5.1±12.6 | <0.001 |
13C-UBT positive, % | 116 (20.6) | 139 (21.6) | 0.395 |
Mean 13C-UBT value in positive results, ‰ | 48.3±39.7 | 22.1±19.2 | <0.001 |
Mean 13C-UBT value in negative results, ‰ | 0.4±0.8 | 0.5±0.4 | 0.513 |
No. of |
0.994 | ||
First | 471 (83.8) | 541 (80.9) | |
Second | 61 (10.9) | 69 (13.0) | |
Third | 30 (5.3) | 35 (6.0) | |
Mean time from |
5.3±1.2 | 5.4±2.1 | 0.696 |
Data are presented as number (%) or mean±SD.
MALT, mucosa-associated lymphoid tissue; ITP, idiopathic thrombocytopenic purpura; 13C-UBT, 13C-urea breath test;
Diagnostic Validity of 13C-UBT Compared to Those of Endoscopic Biopsy Methods
13C-UBT value | Using both endoscopic biopsy-based methods for |
|||
---|---|---|---|---|
Positive | Negative | |||
Meal group (n=60) | ≥2.5‰ | 11 | 9 | PPV 55.0% |
<2.5‰ | 1 | 39 | NPV 97.5% | |
Sensitivity 91.7% | Specificity 81.3% | |||
Control group (n=62) | ≥2.5‰ | 10 | 6 | PPV 62.5% |
<2.5‰ | 1 | 45 | NPV 97.8% | |
Sensitivity 90.9% | Specificity 88.2% |
13C-UBT, 13C-urea breath test;
Diagnostic Validity of 13C-UBT Compared to Those of Endoscopic Biopsy Methods in the Gray Zone (Value of 13C-UBT: 2.0‰–10.0‰)
13C-UBT value | Using both endoscopic biopsy-based methods for |
|||
---|---|---|---|---|
Positive | Negative | |||
Citric acid group (n=15) | ≥2.5‰ | 3 | 6 | PPV 33.3% |
<2.5‰ | 1 | 5 | NPV 83.3% | |
Sensitivity 75.0% | Specificity 45.5% | |||
Control group (n=11) | ≥2.5‰ | 3 | 6 | PPV 33.3% |
<2.5‰ | 0 | 2 | NPV 100.0% | |
Sensitivity 100.0% | Specificity 25.0% |
13C-UBT, 13C-urea breath test;
Risk Factors for Mismatched Results between 13C-UBT and Endoscopic Biopsy-Based Methods after
Variable | 13C-UBT result compared with both endoscopic biopsy-based methods | p-value* | |
---|---|---|---|
Matched group (n=105) |
Mismatched group (n=17) |
||
Sex, male/female | 60 (57.1)/45 (42.9) | 5 (29.4)/12 (70.6) | 0.039 |
Use of citric acid | 50 (47.6) | 10 (58.8) | 0.441 |
Age, yr | 56.2±11.3 | 57.0±12.0 | 1.000 |
Diagnosis | 0.623 | ||
Functional dyspepsia | 19 (18.1) | 3 (17.6) | |
Atrophic gastritis | 23 (21.9) | 6 (35.3) | |
Benign peptic ulcer | 22 (21.0) | 1 (5.9) | |
Gastric dysplasia | 13 (12.4) | 1 (5.9) | |
Early gastric cancer | 20 (19.0) | 5 (29.4) | |
Gastric MALT lymphoma | 8 (7.6) | 1 (5.9) | |
Mean time from |
5.6±0.6 | 5.5±0.8 | 0.831 |
Mean time from 13C-UBT to endoscopic biopsy, wk | 31.8±27.6 | 25.2±21.0 | 0.285 |
Gastric mucosal status | |||
Gastric atrophy | 0.961 | ||
Not investigated | 7 (6.7) | 1 (5.9) | |
Not applicable | 23 (21.9) | 3 (17.6) | |
None | 45 (42.9) | 8 (47.1) | |
Mild | 13 (12.4) | 3 (17.6) | |
Moderate | 14 (13.3) | 2 (11.8) | |
Marked | 3 (2.9) | 0 | |
Gastric intestinal metaplasia | 0.862 | ||
Not investigated | 7 (6.7) | 1 (5.9) | |
None | 54 (51.4) | 10 (58.8) | |
Mild | 20 (19.0) | 2 (11.8) | |
Moderate | 17 (16.2) | 2 (11.8) | |
Marked | 7 (6.7) | 2 (11.8) |
Data are presented number (%) or mean±SD.
13C-UBT, 13C-urea breath test; MALT, mucosa-associated lymphoid tissue.
13C-UBT, 13C-urea breath test;
13C-UBT, 13C-urea breath test;