13C-UBT using an infrared spectrometer for detection of Helicobacter pylori and for monitoring the effects of lansoprazole

Non-invasive diagnostic tests for Helicobacter pylori infection

BACKGROUND

Helicobacter pylori (H pylori) infection has been implicated in a number of malignancies and non-malignant conditions including peptic ulcers, non-ulcer dyspepsia, recurrent peptic ulcer bleeding, unexplained iron deficiency anaemia, idiopathic thrombocytopaenia purpura, and colorectal adenomas. The confirmatory diagnosis of H pylori is by endoscopic biopsy, followed by histopathological examination using haemotoxylin and eosin (H & E) stain or special stains such as Giemsa stain and Warthin-Starry stain. Special stains are more accurate than H & E stain. There is significant uncertainty about the diagnostic accuracy of non-invasive tests for diagnosis of H pylori.

OBJECTIVES

To compare the diagnostic accuracy of urea breath test, serology, and stool antigen test, used alone or in combination, for diagnosis of H pylori infection in symptomatic and asymptomatic people, so that eradication therapy for H pylori can be started.

SEARCH METHODS

We searched MEDLINE, Embase, the Science Citation Index and the National Institute for Health Research Health Technology Assessment Database on 4 March 2016. We screened references in the included studies to identify additional studies. We also conducted citation searches of relevant studies, most recently on 4 December 2016. We did not restrict studies by language or publication status, or whether data were collected prospectively or retrospectively.

SELECTION CRITERIA

We included diagnostic accuracy studies that evaluated at least one of the index tests (urea breath test using isotopes such as 13C or 14C, serology and stool antigen test) against the reference standard (histopathological examination using H & E stain, special stains or immunohistochemical stain) in people suspected of having H pylori infection.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the references to identify relevant studies and independently extracted data. We assessed the methodological quality of studies using the QUADAS-2 tool. We performed meta-analysis by using the hierarchical summary receiver operating characteristic (HSROC) model to estimate and compare SROC curves. Where appropriate, we used bivariate or univariate logistic regression models to estimate summary sensitivities and specificities.

MAIN RESULTS

We included 101 studies involving 11,003 participants, of which 5839 participants (53.1%) had H pylori infection. The prevalence of H pylori infection in the studies ranged from 15.2% to 94.7%, with a median prevalence of 53.7% (interquartile range 42.0% to 66.5%). Most of the studies (57%) included participants with dyspepsia and 53 studies excluded participants who recently had proton pump inhibitors or antibiotics.There was at least an unclear risk of bias or unclear applicability concern for each study.Of the 101 studies, 15 compared the accuracy of two index tests and two studies compared the accuracy of three index tests. Thirty-four studies (4242 participants) evaluated serology; 29 studies (2988 participants) evaluated stool antigen test; 34 studies (3139 participants) evaluated urea breath test-13C; 21 studies (1810 participants) evaluated urea breath test-14C; and two studies (127 participants) evaluated urea breath test but did not report the isotope used. The thresholds used to define test positivity and the staining techniques used for histopathological examination (reference standard) varied between studies. Due to sparse data for each threshold reported, it was not possible to identify the best threshold for each test.Using data from 99 studies in an indirect test comparison, there was statistical evidence of a difference in diagnostic accuracy between urea breath test-13C, urea breath test-14C, serology and stool antigen test (P = 0.024). The diagnostic odds ratios for urea breath test-13C, urea breath test-14C, serology, and stool antigen test were 153 (95% confidence interval (CI) 73.7 to 316), 105 (95% CI 74.0 to 150), 47.4 (95% CI 25.5 to 88.1) and 45.1 (95% CI 24.2 to 84.1). The sensitivity (95% CI) estimated at a fixed specificity of 0.90 (median from studies across the four tests), was 0.94 (95% CI 0.89 to 0.97) for urea breath test-13C, 0.92 (95% CI 0.89 to 0.94) for urea breath test-14C, 0.84 (95% CI 0.74 to 0.91) for serology, and 0.83 (95% CI 0.73 to 0.90) for stool antigen test. This implies that on average, given a specificity of 0.90 and prevalence of 53.7% (median specificity and prevalence in the studies), out of 1000 people tested for H pylori infection, there will be 46 false positives (people without H pylori infection who will be diagnosed as having H pylori infection). In this hypothetical cohort, urea breath test-13C, urea breath test-14C, serology, and stool antigen test will give 30 (95% CI 15 to 58), 42 (95% CI 30 to 58), 86 (95% CI 50 to 140), and 89 (95% CI 52 to 146) false negatives respectively (people with H pylori infection for whom the diagnosis of H pylori will be missed).Direct comparisons were based on few head-to-head studies. The ratios of diagnostic odds ratios (DORs) were 0.68 (95% CI 0.12 to 3.70; P = 0.56) for urea breath test-13C versus serology (seven studies), and 0.88 (95% CI 0.14 to 5.56; P = 0.84) for urea breath test-13C versus stool antigen test (seven studies). The 95% CIs of these estimates overlap with those of the ratios of DORs from the indirect comparison. Data were limited or unavailable for meta-analysis of other direct comparisons.

AUTHORS' CONCLUSIONS

In people without a history of gastrectomy and those who have not recently had antibiotics or proton ,pump inhibitors, urea breath tests had high diagnostic accuracy while serology and stool antigen tests were less accurate for diagnosis of Helicobacter pylori infection.This is based on an indirect test comparison (with potential for bias due to confounding), as evidence from direct comparisons was limited or unavailable. The thresholds used for these tests were highly variable and we were unable to identify specific thresholds that might be useful in clinical practice.We need further comparative studies of high methodological quality to obtain more reliable evidence of relative accuracy between the tests. Such studies should be conducted prospectively in a representative spectrum of participants and clearly reported to ensure low risk of bias. Most importantly, studies should prespecify and clearly report thresholds used, and should avoid inappropriate exclusions.

Two novel laboratory tests facilitating diagnosis of glycine encephalopathy (nonketotic hyperglycinemia)

Glycine encephalopathy (GE), also known as non-ketotic hyperglycinemia, is a life-threatening metabolic disease caused by inherited deficiency of the glycine cleavage system (GCS). GE is characterized by accumulation of a large amount of glycine in serum and cerebrospinal fluids. In typical cases with GE, coma, profound hypotonia, and intractable seizures develop within several days of life. Patients with atypical symptoms may have delayed or missed diagnosis because of non-specific symptoms. It is sometimes problematic to confirm the diagnosis of GE since it requires either invasive liver biopsy for measurement of GCS activity or exhaustive mutational screening of three GCS genes, GLDC, AMT, and GCSH. We herein describe two novel laboratory tests for diagnosis of GE, [1-(13)C]glycine breath test and the multiplex ligation-dependent probe amplification (MLPA) for detection of large deletions in GLDC. The [1-(13)C]glycine breath test has been developed for noninvasive enzymatic diagnosis of GE. Because the GCS generates CO(2) by degradation of glycine, the GCS activity could be evaluated in vivo by measurement of exhaled (13)CO(2) after administration of a stable isotope, [1-(13)C]glycine. The MLPA has been developed for improvement in mutation detection rate in GE: Deletions involving multiple GDLC exons are prevalent among GE patients, but cannot be detected by the exon-sequencing analysis. Two novel diagnosis methods would facilitate diagnosis of hyperglycinemic patients as having GE.

Rapid diagnosis of glycine encephalopathy by13C-glycine breath test

OBJECTIVE

It is currently problematic to confirm the clinical diagnosis of glycine encephalopathy, requiring either invasive liver biopsy for enzymatic analysis of the glycine cleavage system or exhaustive mutation analysis. Because the glycine cleavage system breaks down glycine generating carbon dioxide, we suppose that the glycine cleavage system activity could be evaluated in vivo by measuring exhaled (13)CO(2) after administration of [1-(13)C]glycine.

METHODS

The [1-(13)C]glycine breath test was performed in 10 control subjects and 5 glycine encephalopathy patients with GLDC mutation, including 1 patient with mild glycine encephalopathy.

RESULTS

All the patients showed lower (13)CO(2) excretion than any control subject.

INTERPRETATION

Not only typical GE but also atypical GE can be reliably diagnosed by the (13)C-glycine breath test. Because it is rapid, non-invasive, and requires little expertise, the breath test could be useful as a standard test for diagnosing GE.

Analytical techniques in biomedical stable isotope applications: (isotope ratio) mass spectrometry or infrared spectrometry?

An overview is presented of biomedical applications of stable isotopes in general, but mainly focused on the activities of the Center for Liver, Digestive and Metabolic Diseases of the University Medical Center Groningen. The aims of metabolic studies in the areas of glucose, fat, cholesterol and protein metabolism are briefly explained, as well as the principle of breath testing and the techniques to study body composition and energy expenditure. Much attention is paid to the analytical considerations based upon metabolite concentrations, sample size restrictions, the availability of stable isotope labelled substrates and dose requirements in relation to compound-specific isotope analysis. The instrumental advantages and limitations of the generally used techniques gas chromatography/reaction/isotope ratio mass spectrometry and gas chromatography/mass spectrometry are described as well as the novelties of the recently commercialised liquid chromatography/combustion/isotope ratio mass spectrometry. The present use and future perspective of infrared (IR) spectrometry for clinical and biomedical stable isotope applications are reviewed. In this respect, the analytical demands on IR spectrometry are discussed to enable replacement of isotope ratio mass spectrometry by IR spectrometry, in particular, for the purpose of compound-specific isotope ratio analysis in biological matrices.

Review article: 13C-urea breath test in the diagnosis of Helicobacter pylori infection -- a critical review

The urea breath test is a non-invasive, simple and safe test which provides excellent accuracy both for the initial diagnosis of Helicobacter pylori infection and for the confirmation of its eradication after treatment. Some studies have found no differences between urea breath test performed under non-fasting conditions. The simplicity, good tolerance and economy of the citric acid test meal probably make its systematic use advisable. The urea breath test protocol may be performed with relatively low doses (<100 mg) of urea: 75 mg or even 50 mg seem to be sufficient. With the most widely used protocol (with citric acid and 75 mg of urea), excellent accuracy is obtained when breath samples are collected as early as 10-15 min after urea ingestion. A unique and generally proposed cut-off level is not possible because it has to be adapted to different factors, such as the test meal, the dose and type of urea, or the pre-/post-treatment setting. Fortunately, because positive and negative urea breath test results tend to cluster outside of the range between 2 and 5 per thousand, a change in cut-off value within this range would be expected to have little effect on clinical accuracy of the test.

Cut-off point, timing and pitfalls of the 13C-urea breath test as measured by infrared spectrometry

BACKGROUND

The best timing and the best cut-off level of the 13C-urea breath test have not yet been well established.

AIMS

To evaluate the cut-off value and the influence of medication on the 13C-urea breath test as measured by infrared spectrometry.

METHODS

A series of 223 patients, sent for endoscopy performed 13C-urea breath test in fasting conditions with 75 mg of 13C-urea and 20 ml of citric acid. Breath samples were collected before and then 10, 20, 25 and 30 minutes after ingestion. As gold standard, histological examination of gastric biopsies was used. A questionnaire was completed concerning the intake of medication, likely to influence the test, in the 2 months preceding the test. Sensitivity, specificity, positive predictive value and negative predictive value at 10, 20, 25 and 30 minutes at different cut-off values (3, 3. 5, 4, 4. 5, 5.0 0/00 DOB] were calculated.

RESULTS

A total of 182 patients did not take medication. There was no significant difference between the different cut-off levels at different times. Compared with the group of 41 patients who did take medication, likely to influence the test, the differences were significant (Fisher exact test).

CONCLUSION

There was no significant difference between the different cut-off values. A 10-minute test with a cut-off level between 4 and 5% delta over baseline (sensitivity: 100%, specificity: 95%) is, therefore, proposed. To avoid false negative results due to unknown intake of medication, every patient submitted to the 13C-urea breath test should fill out a questionnaire.

Accurate diagnosis of Helicobacter pylori. 13C-urea breath test

The preferred schema for management of Helicobacter pylori infection is diagnosis, treatment, and confirmation of cure. The 13C-urea breath test is ideal for active H. pylori infection for those in whom endoscopy is not required (e.g., those in whom cancer is not suspected) because it offers the combination of simplicity, accuracy, reliability, and absence of exposure to radioactivity. New versions of the test also offer increasing simplicity and lower costs.

The application of infrared spectroscopy to breath CO2 isotope ratio measurements and the risk of spurious results

Stable CO2 isotope breath tests are established as a valuable tool in diagnostic and investigative medicine with the potential to become more prominent in the future. However, their development and widespread clinical use is limited by the requirement of isotope ratio mass spectroscopic analysis. To overcome this restriction alternative analytical techniques have been developed; the most promising, offering relative simplicity and lower costs, are those instruments using infrared spectroscopy. Clinical investigations using such instruments show them to perform well but very little attention has been given to the possibility of interference from the infrared absorption spectrum of other compounds in the breath. To provide an unambiguous answer to this concern we have analysed literature on over 200 detected breath compounds and their infrared absorption spectra to identify any absorption bands coincident with the nu3 absorption band of CO2. It was found that only five breath trace compounds possess coincident fundamental absorption bands, none of which pose the risk of spurious results. We conclude that the 13C16O2/12C16O2 ratio can confidently be measured for isotopic breath tests using an infrared spectrometer, the position of the nu3 absorption band of CO2 in the infrared spectrum precluding any discernible risk of spurious measurements due to coincidental absorption bands.

Application of isotope-selective nondispersive infrared spectrometry (IRIS) for evaluation of [13C]octanoic acid gastric-emptying breath tests: comparison with isotope ratio–mass spectrometry (IRMS)

Suitability of isotope-selective nondispersive infrared spectrometry (IRIS) for evaluation of [13C]octanoic acid gastric-emptying breath test was assessed and compared with standard isotope ratio–mass spectrometry (IRMS). The estimated bias of IRMS and IRIS measurements of baseline-corrected 13CO2exhalation amounted to ± 0.1 and ± 0.6 Δδ values (n = 360), respectively. In breath tests performed on 60 diabetic patients, the gastric emptying parameters were calculated by nonlinear regression analysis of the time course of 13CO2exhalation: half-emptying time (t1/2,breath, 90 ± 39 min), lag phase (tlag,breath, 34 ± 27 min), and gastric emptying coefficient (GEC, 2.9 ± 0.5). A reasonable linear correlation was found between the two methods (y = IRIS, x = IRMS) with respect to Δδ values (y = 0.35 + 0.92x, r = 0.985, Sy|x = ±0.6, n = 1116) and a rather good agreement of the computed gastric emptying parameters was obtained (t1/2,breath: y = 0.99x + 4.06, Sy|x = ±6.3; tlag,breath: y = 0.97x + 0.96, Sy|x = ±3.4; GEC: y = 0.97x − 0.01, Sy|x = ±0.09).