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Influence of age on 13C-urea breath test results in children
A Kindermann1, H Demmelmair, B Koletzko
1Kinderklinik, University of Munich, Germany.
Insights
The 13C-urea breath test is effective for diagnosing Helicobacter pylori infection, but age significantly impacts results, especially in young children. A gray zone is recommended over a threshold due to potential false positives in this group.
Area of Science:
- Pediatric Gastroenterology
- Infectious Disease Diagnostics
- Breath Analysis
Background:
- The 13C-urea breath test (13C-UBT) is a non-invasive method for diagnosing Helicobacter pylori infection.
- Validation of 13C-UBT in infants and young children is limited.
- Age-related variations in 13C-UBT performance require investigation.
Purpose of the Study:
- To validate the 13C-urea breath test in a large pediatric population.
- To assess the influence of age on 13C-UBT accuracy.
- To determine optimal cutoff values and gray zones for H. pylori diagnosis in children.
Main Methods:
- 1499 children (2 months to 18 years) underwent 13C-UBT.
- Breath samples were collected at baseline, 15, and 30 minutes post-ingestion of 13C-urea.
- Test results were mathematically analyzed, and a subgroup was validated against histology and rapid urease tests.
Main Results:
- Optimal cutoff values were determined as 4.7/1000 at 15 minutes and 5.0/1000 at 30 minutes.
- Age negatively correlated with delta-over-baseline (DOB) values.
- Younger children (<6 years) showed higher DOB values and a greater proportion in the gray zone, leading to lower specificity and positive predictive values.
Conclusions:
- The 13C-urea breath test demonstrates good separation of results, but a gray zone is more appropriate than a single threshold due to age effects.
- Infants and young children are at higher risk for false-positive results, necessitating adapted cutoff values.
- Further validation studies are recommended for the pediatric age group, particularly for younger children.
Background:
The 13C-urea breath test for diagnosis of Helicobacter pylori infection has not been validated in infants and young children. The influence of age on the test results was studied by conventional validation against invasive methods and by mathematical estimation in a large pediatric population.
Methods:
The breath test was performed in 1499 children aged 2 months to 18 years. After a fasting period of 4 hours or more, 75 mg 13C-urea was ingested with cold apple juice, breath samples were taken at baseline and at 15 and 30 minutes. The distribution of the natural logarithms of the delta-over baseline (DOB) values were calculated, and the optimal cutoff values between positive and negative test results and gray zones with a risk of misclassification more than 10% were determined for both time points. In a subgroup of 149 children results of the breath test were compared with concordant results of histology and rapid urease test; 53 of them were less than 6 years of age.
Results:
Logarithmic results of 1499 breath tests revealed two normally distributed subgroups with minimal overlap. The calculated optimal cutoff values were 4.7/1000 at 15 minutes and 5.0/1000 at 30 minutes. At 30 minutes, only 2.6% of all results were in the calculated gray zone (2.6-6.5/1000). Age was negatively correlated to DOB values of both negative (r = -0.223) and positive results (r = -0.291; P < 0.001). Breath test-negative and -positive children 6 or less years of age had significantly higher mean DOB values (P < 0.02) and a larger proportion of results within the gray zone than older children. Compared with biopsy-based results, the least discrepancies occurred at a cutoff of 5.0/1000: 0 of 61 infected (sensitivity 100%) and 6 of 88 noninfected children. Because five of the false-positive results were obtained in children less than 6 years of age, specificity and positive predictive values were lower in this age group than in older patients (88.1% vs. 97.8% and 68.8% vs. 98.0%, respectively).
Conclusions:
Under the applied conditions, the 13C-urea breath test shows an excellent separation between positive and negative results. Because of some overlap and a strong age effect, definition of a gray zone appears more meaningful than a threshold value. Because infants and young children have a high risk for false-positive breath test results, the values for cutoff and gray zones may have to be adapted. Further validation studies against invasive methods are warranted in this age group.