Radiology and Oncology | Ljubljana | Slovenia | www.radioloncol.com Radiol Oncol 2022; 56(3): 390-397. doi: 10.2478/raon-2022-0034 390 research article Abbreviated 13 C-mixed triglyceride breath test for detection of pancreatic exocrine insufficiency performs equally as standard 5-hour test in patients after gastrectomy performed for gastric cancer Darko Siuka 1 , Kristina Kumer 2 , Borut Stabuc 1,3 , David Stubljar 4 , David Drobne 1,3 , Rado Jansa 1,3 1 Department of Gastroenterology, University Medical Centre Ljubljana, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia 2 Institute of Clinical Chemistry and Biochemistry, University Medical Centre Ljubljana, Ljubljana, Slovenia 3 Medical Faculty, University of Ljubljana, Ljubljana, Slovenia 4 In-Medico, Research and Development, Metlika, Slovenia Radiol Oncol 2022; 56(3): 390-397. Received 28 March 2022 Accepted 12 June 2022 Correspondence to: Darko Siuka, M.D., Department of Gastroenterology, Japljeva 2, 1000 Ljubljana, University Medical Centre Ljubljana, Ljubljana, Slovenia, E-mail: darko_siuka@yahoo.com, Phone: +386 41 958 682; and Assist. Prof. Rado Janša, M.D, Ph.D, Department of Gastroenterology, Japljeva 2, 1000 Ljubljana, University Medical Centre Ljubljana, Ljubljana, Slovenia, E-mail: rado.jansa@gmail.com Disclosure: No potential conflicts of interest were disclosed. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Background. 13 C-mixed triglyceride breath test ( 13 C-MTGT) is a non-invasive test for the detection of moderate and severe pancreatic exocrine insufficiency (PEI), but it requires prolonged breath sampling. The aim of this study was to determine the diagnostic power of abbreviated 13 C-MTGT in detecting PEI in patients after subtotal and total gastrec- tomy performed due to gastric cancer. Subjects and methods. This cross-sectional observational study included 3 groups of subjects; healthy controls, patients with subtotal and patients with total gastrectomy. Demographic and clinical data of patients were collected. Stool samples to determine faecal elastase (Fe-1) and chymotrypsin were collected and measured by ELISA. All sub- jects performed 5-hour 13 C-MTGT breath test. The concentration and relative content of 13 C in exhaled air was meas- ured by isotope ratio mass spectrometer (IRMS). PEI was confirmed as values of 13 C-exhalation < 26.8% after 5 hours. Results. Overall, 65 participants were included into analysis, 22 having PEI (n = 11 after subtotal and n = 11 after total gastrectomy, both performed for gastric cancer). 13 C-MTGT breath test showed difference in percent of exhaled 13 C between PEI and non-PEI patients already after 60 minutes (p = 0.034). Receiver operating characteristic (ROC) curve analysis showed that cut-off value of 13.74% after 150 minutes is showing equivalent diagnostic power to the longer test with sensitivity and specificity both above 90% for the exclusion of PEI in patients after subtotal and/or total gastrectomy. Conclusions. In this study abbreviated 13 C-MTGT test could be shortened from 5 to 2.5 hours without decrease in its diagnostic accuracy for detection of PEI in patients with subtotal or total gastrectomy performed for gastric cancer. This allows significant time savings in the diagnostics of PEI in this subgroup of patients. Key words: abbreviated 13 C-mixed triglyceride breath test; pancreatic exocrine insufficiency; gastrectomy; faecal elastase; gastric cancer Introduction Pancreatic exocrine insufficiency (PEI) is a malab- sorption syndrome caused by deficiency or inacti- vation of pancreatic enzymes and/or bicarbonate in the gastrointestinal tract. This leads to maldiges- tion, malabsorption, and malnutrition with conse- quent higher morbidity, higher long-term mortal- Radiol Oncol 2022; 56(3): 390-397. Siuka D et al. / Abbreviated breath test 391 ity, and reduced quality of life. 1 We distinguish primary PEI, in which the mechanism is tied to the pancreas itself (various diseases of the pancre- atic parenchyma or pancreatic duct) and second- ary PEI, which is often unrecognized because the mechanisms of PEI are extrapancreatic. 1,2 Secondary PEI also includes PEI in patients with altered anatomy due to gastric surgery (subtotal and total gastrectomy). Subtotal and total gas- trectomy are common surgical procedures, very often performed in patients with gastric tumours, mostly with resectable adenocarcinoma. 3 Thus, be- sides chronic pancreatitis, diabetes mellitus (DM), coeliac disease, cystic fibrosis, inflammatory bowel disease and pancreatic cancer, the surgical proce- dures are the most common causes of PEI. In these diseases, there is a presence of decreased exocrine secretion. 2,4 The pathophysiology of PEI post-gastrectomy is attributed to several factors. Firstly, the loss of the gastric reservoir leads to an absence of the ini- tial mechanical digestion of food and faster transit of osmotically active food particles into the small intestine. The less digested food particles are less potent stimulators of cholecystokinin (CCK), re- sulting in a decrease in endogenous stimulation to release digestive enzymes. Secondly, loss of duode- nal transit of food with reconstructive techniques bypassing the duodenum, such as Billroth-II (B2) and Roux-en Y (RY) reconstructions, leads to less CCK being released in response to the detection of chyme in the duodenum and upper jejunum. Thirdly, the release of pancreatic enzymes is not coordinated with the intestinal transit of food and inadequate mixing occurs (post-cibal asynchrony), leading to ineffective digestion. Finally, truncal vagotomy has been shown to reduce secretin- stimulated pancreatic trypsin and lipase secretion by 50-60%. This is attributed to the interruption of the cephalic phase of pancreatic digestion, during which sensory inputs are transmitted to the exo- crine pancreas through the vagus nerve. 5 PEI has great impact on the quality of life, mor- bidity and mortality of these patients also in pa- tients after gastrectomy, especially if the condition remains unrecognised. 6 Diagnostic tests for the direct pancreatic func- tion are gold standard as they are most sensi- tive for the detection of PEI but are invasive. The alternative are non-invasive tests such as faecal elastase-I (Fe-1), however with low sensitivity and specificity falls in diagnosing mild to moderate PEI. 7,8 The specificity of this test seems to be even reduced after total and subtotal gastrectomy. 8-10 Therefore, diagnostics of PEI patients after gastrec- tomy may be difficult, as faecal elastase (Fe-1), the standard of PEI detection, may be of normal range values. The sensitivity of these tests is low due to its extrapancreatic mechanism of PEI in these pa- tients. 11 On the other hand, the 13 C mixed triglycer- ide breath test ( 13 C-MTGT) is a non-invasive assay that indirectly evaluates pancreatic lipase activity and pancreatic exocrine function. The disadvan- tage of this breath test is the long time required for the test (5 −6 hours). This is time consuming for patients and for medical staff, so there is a great need for a test that will be of shorter duration and therefore more patient-friendly. 1,2,11-14 Limited number of studies have tested patients with sus- pected PEI who underwent a long 6-hour or modi- fied, shortened 13 C-MTGT breath test and showed some good results for shortening the test from 6 to 4 hours. 15-17 As mentioned, the long time period of breath sampling and immobilization is a drawback and the period less than 6 hours led to decreased sensitivity of 13 C-MTGT. Even though with shorter times (1-5 hours), sensitivity and specificity ranged from 73% to 85% and 83% to 100%, respectively. 16 However, none of these studies were performed in a subgroup of patients after subtotal and total gastrectomy with test whether even shorter dura- tion of test can be performed. We hypothesised that in this specific subgroup of post-gastrectomy patients the 13 C-MTGT breath test could be signifi- cantly shortened due to the changed anatomy after resection of the stomach. Since this has not been explored before we performed this prospective ob- servational study that specifically focused on pa- tients with resectable gastric cancer. Therefore, the purpose of our study is to deter- mine the diagnostic value of abbreviated 13 C mixed triglyceride respiratory test ( 13 C-MTGT) for the evaluation of PEI in patients after subtotal and to- tal gastrectomy performed for gastric cancer. The goal was to determine and confirm the equivalence of the sensitivity of the shortened and standard 13 C-MTGT breath test in detecting PEI, while de- termining the optimal required cut-off time of the abbreviated 1 3 C-MTGT breath test with preserved sensitivity and specificity of PEI determination. Subjects and methods Participants The study was designed as a cross-sectional, ob- servational study from a single centre, University Medical Centre of Ljubljana. The subjects were Radiol Oncol 2022; 56(3): 390-397. Siuka D et al. / Abbreviated breath test 392 divided into three groups: healthy controls, sub- jects with subtotal gastrectomy and subjects with total gastrectomy. The group of healthy controls served as a base population for better estimation of diagnostic accuracy for abbreviated 13 C-MTGT breath test. All subjects were adults, 18 years of age or older. Before voluntary participation all partici- pants needed to give the written informed consent. The study design and execution were approved by National Ethics Committee of Republic of Slovenia for Medical Ethics (registration number 140/02/10). Exclusion criteria for patients in both gastrecto- my groups, as well as in the group of healthy indi- viduals, were conditions often associated with PEI (type 1 and 2 diabetes, celiac disease, acute pancrea- titis, chronic pancreatitis, surgical conditions such as pancreatectomy, pancreatic head tumours, etc.). Since we studied the impact of changed anatomy af- ter gastric surgery on the performance of 13 C-MTGT breath test we excluded patients with primary metastatic gastric cancer. The other exclusion crite- ria were other metastatic diseases, liver disease in which bile secretion is impaired, inability to partici- pate in research due to psychiatric illness, pregnan- cy, lactation and allergy to butter or chocolate (these patients are unable to performed the test). Healthy controls were without any clinical signs and symp- toms of gastric diseases, normal pancreatic elastase and without concomitant diseases. Upon inclusion, demographic and clinical data on patients (gender, age, associated diseases, regu- lar therapy, eating habits, smoking, coffee drinking, physical activity, weight, height, calculated body mass index [BMI]) were collected. Gastrointestinal symptoms and the degree of expression (diar- rhoea, steatorrhea, abdominal pain, weight loss, flatulence, anorexia, increased appetite) were also recorded. Blood analyses Moreover, peripheral blood for haemogram, amyl- ase, lipase, CRP, hepatogram (AST, ALT, total and direct bilirubin, AF and GGT, prothrombin time, INR), electrolytes, urea, creatinine, calcium, lipi- dogram was drawn from all subjects in the morn- ing after a 12-hour fast. Subjects submitted the first morning urine for amylase, lipase, glucose and stool to determine faecal elastase and faecal chymo- trypsin. Analysing pancreatic faecal elastase (FE-1) and chymotrypsin levels subjects needed to pass the stool samples. The concentrations were meas- ured by Enzyme-Linked ImmunoSorbent Assay method (ELISA) and detected photometrically. Performance of 13 C-mixed triglyceride breath test ( 13 C-MTGT) All subjects underwent our standardized 13 C-MTGT breath test that took in total 5 hours (= 300 min). This is in line to already published pro- cedure and is standard of care in our institution. 12 The first exhalation is done as a baseline, before eating test meal and then at 30-minute intervals. After the first exhalation the subject ate a test meal consisting of two slices of white bread, each weigh- ing 100 g, with one piece of bread accompanied by a piece of butter weighing 20 g. With another piece of bread, subjects consumed 30 g of choco- late spread (Nutella, Ferrero Rocher, Germany). The chocolate cream was mixed with 250 mg of a substrate of mixed triglycerides (1,3-distearyl- 2-octanyl glycerol) labelled with the isotope 13 C (Euriso-top, Saarbrücken, Germany). After eating the bread, the subjects drank 200 mL of water. They were requested to sit throughout the whole exami- nation. The subjects blew exhaled air into test tubes at intervals of 30 minutes. Based on the difference in concentration between 13 C and 12 C, the relative isotope ratio (IRMS) mass spectrometer was used to determine the relative 13 C content of exhaled CO 2 . The concentration of 13 C in exhaled air and measurement of the ratio of 13 C to 12 C in exhaled CO 2 were analysed. The measured isotope ratio in the samples were expressed as the relative differ- ence ( δ per mL in %) and subtracted from the base- line. The values of 13 C exhalation were compared with the standard parameter of 13 C of healthy vol- unteers. PEI was confirmed according to Keller et al. if patients had a ratio of 13 C below 26.8%. 17 Statistical analysis Statistical analyses were performed using the soft- ware package SPSS 21.0 (IBM Inc., Chicago, USA). Normally distributed variables were expressed as arithmetic mean and standard deviation, and One- Way ANOVA test was used for comparisons be- tween variables. In case of abnormally distributed variables the differences between continuous vari- ables were analysed by the nonparametric Mann- Whitney test. Differences between categorical vari- ables and calculation of the positive/negative pre- dictive values (PPV, NPV) were performed by us- ing the Pearson’s chi-square test. The optimal time of the 13 C MTGT breath test was tested with a re- ceiver operating characteristic (ROC) analysis with area under curve (AUC), sensitivity and specificity. Respective cut-off values were performed for each Radiol Oncol 2022; 56(3): 390-397. Siuka D et al. / Abbreviated breath test 393 Results Overall, 65 participants were included into analy- sis and were then divided into 3 groups: (i) healthy controls (n = 20), (ii) group of patients with subtotal resection (n = 23) and (iii) group of patients with total gastrectomy (n = 22). Baseline characteristics timepoint of 13 C measurements, and their diagnos- tic accuracy for PEI was calculated. Calculation of statistical power assumed a sample of 20 patients in each group with 80% in order to confirm or re- fuse the hypothesis when assuming an error α be- low 0.05. Thus, statistical significance for all tests was determined as p-value below 0.05. TABLE 1. Basic characteristics of subjects enrolled in the study All subjects N = 65 Healthy controls N = 20 Subtotal resection N = 23 Total resection N = 22 p-value Sex M/F 38 (58.5%)/27 (41.5%) 7/13 14/9 17/5 0.020 Age [years] 59.3 ± 16.9 43.4 ± 13.4 62.7 ± 13.8 70.2 ± 11.4 < 0.001 Age group < 0.001 18 −40 y 8 (12.3%) 7 (35.0%) 1 (4.3%) 0 41 −65 y 35 (53.8%) 13 (65.0%) 15 (65.3%) 7 (31.8%) > 65 let 22 (33.8%) 0 7 (30.4%) 15 (62.2%) Weight [kg] 67.9 ± 15.3 66.6 ± 16.0 70.0 ± 13.7 67.0 ± 16.8 0.738 Height [m] 1.7 ± 0.1 1.7 ± 0.1 1.7 ± 0.1 1.7 ± 0.1 0.576 BMI 23.2 ± 4.2 22.3 ± 4.3 24.1 ± 4.0 23.0 ± 4.2 0.333 PEI (< 26.8) # 22 (33.8%) 0 11 (47.8%) 11 (50.0%) 0.001 Pancreatic elastase (mcg/g) 349.8 ± 182.1 440.2 ± 126.3 312.2 ± 188.8 307.0 ± 195.2 0.026 Normal 50 (76.9%) 20 (100%) 16 (69.6%) 14 (63.6%) Mild decrease 7 (10.8%) 0 2 (8.7%) 5 (22.7%) Moderate decrease 2 (3.1%) 0 2 (8.7%) 0 Severe decrease 6 (9.2%) 0 3 (13.0%) 3 (13.6%) Chymotrypsin (U/g) 225.3 ± 160.8 301.7 ± 187.4 181.9 ± 130.3 201.3 ± 144.8 0.033 Normal 52 (80.0%) 20 (100%) 14 (60.9%) 18 (81.8%) PEI 13 (20.0%) 0 9 (39.1%) 4 (18.2%) Smoking 0.445 No 56 (86.2%) 19 (95.0%) 18 (78.3%) 19 (86.4%) < 15 cigarettes /day 4 (6.2%) 0 3 (13.0%) 1 (4.5%) > 15 cigarettes /day 5 (7.7%) 1 (5.0%) 2 (8.7%) 2 (9.1%) Coffee 0.136 No 23 (35.4%) 4 (20.0%) 7 (30.4%) 12 (54.5%) 1 −2 cups /day 29 (44.6%) 10 (50.0%) 12 (52.2%) 7 (31.8%) > 2 cups /day 12 (18.5%) 6 (30.0%) 3 (13.0%) 3 (13.6%) Alcohol 0.108 No 47 (72.3%) 12 (60.0%) 15 (65.2%) 17 (77.3%) < 2 units/day 16 (24.6) 8 (40.0%) 5 (21.7%) 3 (13.6%) > 2 units/day 2 (3.1%) 0 0 2 (9.1%) Cholesterol (mmol/l) 4.5 ± 0.8 4.5 ± 0.7 4.4 ± 1.0 4.5 ± 0.7 0.736 HDL_cholesterol 1.5 ± 0.5 1.5 ± 0.4 1.4 ± 0.4 1.5 ± 0.6 0.637 LDL_cholesterol 2.5 ± 0.7 2.5 ± 0.6 2.5 ± 0.8 2.5 ± 0.7 0.921 Triglycerides 1.2 ± 0.8 0.9 ± 0.2 1.2 ± 0.9 1.5 ± 0.9 0.033 # According to the 13 C-mixed triglyceride breath test; BMI = body mass index; F = female; M = male; PEI = pancreatic exocrine insufficiency Radiol Oncol 2022; 56(3): 390-397. Siuka D et al. / Abbreviated breath test 394 of subject at enrolment are presented in Table 1. According to the baseline the groups of patients with gastrectomy differed in age and in gender ra- tio when compared to the healthy controls. Moreover, PEI were identified in patients after subtotal and total gastrectomy with 13 C-MTGT breath test, FE-1, and faecal chymotrypsin, but not with 100% coverage. 13 C-MTGT breath test after 300 minutes with a score < 26.8% was taken as a reference to determine PEI 17,18 , and at the end de- termined 22/45 (48,9%) patients with PEI. Approximately half of the patients in group of patients after subtotal and total gastrectomy had PEI confirmed. Meanwhile, no significant differ- ences in patients’ characteristics or habits were de- termined between patients with PEI and patients without PEI (Table 2). After performing 13 C-MTGT breath test there has been an observation of difference in percent of exhaled 13 C between the patients without PEI and patients with PEI soon after 2 measurements at 60 minutes (Table 3). In later timepoints, after 3 rd measurement at 90 minutes the differences were increasing (p < 0.001) confirming that the abbrevi- ated of 13 C-MTGT breath test to exclude PEI can be reliably used in patients after gastrectomy. The required test time was not shorter in pa- tients with total gastrectomy than in those after subtotal gastrectomy (Table 4) as no differences were observed in any of the timepoints. The optimal duration of the abbreviated 13 C-MTGT breath test was determined by cut-off values and ROC analysis showing that shorten- ing the test to 150 minutes with the cut-off value of 13.74% is showing high sensitivity and specific- ity, both above 90% and high PPV and NPV for the exclusion of PEI in patients after subtotal and/ or total gastrectomy. The reliability of the abbrevi- ated 13 C-MTGT breath test showed an equivalence of sensitivity in comparison to the standard, 5-hour 13 C-MTGT breath test (Table 5, Figure 1) in this subgroup of patients. Discussion PEI in patients after subtotal and total gastrectomy should be detected as early as possible and with a highly sensitive test as early treatment of PEI im- proves outcome for these patients. Diagnostic of measuring fecal elastase in stool is most commonly performed, but it is important to supplement or even substitute it with more sensitive tests such as the 13 C-MTGT breath test as it is crucial to treat PEI TABLE 2. Differences between patient with positive and negative pancreatic exocrine insufficiency (PEI) determined by 13 C-mixed triglyceride breath* PEI p-value Positive < 26.8 (n = 22) Negative > 26.8 (n = 43) Sex Male/Female 16/6 22/21 0.095 Age [years] 63.5 ± 12.8 57.2 ± 18.5 0.157 Weight [kg] 72.8 ± 15.8 65.5 ± 14.7 0.069 Height [m] 1.7 ± 0.1 1.7 ± 0.1 0.447 BMI 24.4 ± 4.0 22.5 ± 4.1 0.082 Smoking 0.181 No 17 (77.3%) 39 (90.7%) < 15/day 3 (13.6%) (2.3%) 15/day 2 (9.1%) 3 (7.0%) Coffee 0.107 No 9 (40.9%) 14 (32.6%) 1 −2/day 12 (54.5%) 17 (39.5%) > 2/day 1 (4.5%) 11 (25.6%) Alcohol 0.527 No 14 (63.6%) 33 (76.7%) < 2 units/day 7 (31.8%) 9 (20.9%) > 2 units/day 1 (4.5%) 1 (2.3%) Cholesterol 4.5 ± 0.8 4.4 ± 0.8 0.523 HDL_cholesterol 1.3 ± 0.4 1.5 ± 0.5 0.091 LDL_cholesterol 2.6 ± 0.8 2.5 ± 0.6 0.630 Triglycerides 1.6 ± 1.0 1.0 ± 0.6 0.011 * Determined by 13 C-mixed triglyceride breath test @300 min: PEI group 19.6 ± 9.5; non-PEI group 40.9 ± 10.4 (< 0.001); BMI = body mass index TABLE 3. Percent of exhaled 13 C in patients with pancreatic exocrine insufficiency (PEI) and without PEI at respective timepoint of 13 C measurement PEI p-value* Positive < 26.8 (n = 22) Negative > 26.8 (n = 43) 30 min 0.29 ± 0.71 0.47 ± 0.62 0.233 60 min 0.97 ± 1.87 2.23 ± 2.00 0.034 90 min 2.05 ± 2.96 5.23 ± 3.24 < 0.001 120 min 3.53 ± 3.94 8.85 ± 4.05 < 0.001 150 min 8.39 ± 6.36 20.88 ± 5.96 < 0.001 180 min 10.12 ± 7.03 25.07 ± 6.63 < 0.001 210 min 12.21 ± 7.37 29.33 ± 7.29 < 0.001 240 min 14.50 ± 7.66 33.52 ± 8.06 < 0.001 270 min 17.10 ± 8.25 37.33 ± 9.09 < 0.001 300 min 17.72 ± 9.44 40.76 ± 10.43 < 0.001 *Determined by Mann-Whitney test Radiol Oncol 2022; 56(3): 390-397. Siuka D et al. / Abbreviated breath test 395 early in these patients. However, the execution of this test takes significant time, generally 5 −6 hours. The test is feasible as soon as patients are able to eat, and all of our patients have passed the test within 6 months of gastrectomy. All patients underwent a C13 breath test less than 6 months after gastrectomy. Previously it has been shown that the time required for a breath test in patients with fast food passage in the upper gas- trointestinal tract may be shorter 16,17 , so it is still necessary to determine the most optimal time re- quired for breath test in patients with gastrectomy where changed anatomy impacts test meal transi- tion time even more. The aim of the current study was to find the optimal duration and cut-off value for the 13 C-MTGT breath test in secondary PEI at respective timepoints in two groups of patients, namely with subtotal and with total gastrectomy performed for gastric cancer. Be cause the time after gastrectomy in which patients underwent 13C-MTGT breath test after gastrectomy was too short, laboratory-detectable malnutrition had not yet occurred. If the 13C-MTGT breath test would be performed after a longer period of time, we would expect reduced laboratory nutritional mark- ers at the same time as the pathological 13C-MTGT breath test, which in principle would not affect the 13C-MTGT breath test itself. Other conditions that could simultaneously lead to PEI and consequently a change in the 13C-MTGT breath test could be ruled out by additional investi- gations (DM, etc). Our analysis showed that the diagnostic sensi- tivity and specificity of the abbreviated 13 C-MTGT breath test for detection of PEI was equivalent to the sensitivity of the longer 5-hour 13 C-MTGT breath TABLE 4. Percent of exhaled 13 C according to diagnosis of in respective timepoint of C13 measurement Healthy controls (n = 20) Diagnosis p-value* p-value** Subtotal resection (n = 23) Total resection (n = 22) 30 min 0.54 ± 0.74 0.32 ± 0.71 0.38 ± 0.51 0.700 0.936 60 min 2.28 ± 2.32 1.27 ± 1.88 1.92 ± 1.86 0.193 0.534 90 min 5.12 ± 3.76 3.15 ± 3.12 4.32 ± 3.45 0.202 0.495 120 min 8.63 ± 4.76 5.669 ± 4.54 7.04 ± 4.63 0.162 0.593 150 min 20.60 ± 7.09 13.96 ± 9.00 15.87 ± 8.11 0.056 0.714 180 min 24.91 ± 7.86 16.94 ± 10.74 18.77 ± 9.00 0.031 0.790 210 min 29.31 ± 8.61 20.45 ± 12.33 21.51 ± 9.55 0.023 0.937 240 min 33.67 ± 9.26 24.18 ± 13.81 24.14 ± 10.11 0.014 1.000 270 min 37.71 ± 9.82 28.04 ± 15.26 26.47 ± 10.63 0.010 1.000 300 min 41.14 ± 10.40 32.01 ± 17.21 28.51 ± 11.00 0.008 0.658 * Mann-Whitney test; ** Tukey Post-hoc analysis between subtotal and total resection groups TABLE 5. Cut-off values for prediction of non-pancreatic exocrine insufficiency (non-PEI) within respective timepoints in all subjects All patients cut-off AUC 95% CI p-value Sensitivity Specificity PPV NPV 30 min 0.25 0.591 0.444 −0.737 0.233 53.5% 68.2% 42.9% 76.7% 60 min 1.16 0.662 0.522 −0.801 0.034 67.4% 54.5% 46.2% 74.4% 90 min 3.79 0.776 0.654 −0.898 < 0.001 67.4% 81.8% 56.3% 87.9% 120 min 4.71 0.845 0.738 −0.952 < 0.001 88.4% 72.7% 76.2% 86.4% 150 min 13.74 0.929 0.853 −1.000 < 0.001 93.0% 90.9% 87.0% 95.2% 180 min 16.19 0.938 0.869 −1.000 < 0.001 93.0% 90.9% 87.0% 95.2% 210 min 18.64 0.948 0.888 −1.000 < 0.001 95.3% 90.9% 90.9% 95.3% 240 min 20.85 0.962 0.902 −1.000 < 0.001 97.7% 90.9% 95.2% 95.5% 270 min 25.71 0.962 0.891 −1.000 < 0.001 97.7% 95.5% 95.5% 97.7% 300 min 26.95 0.962 0.889 −1.000 < 0.001 100% 95.5% 100% 97.7% AUC = area under curve; NPV = negative predictive values; PPV = positive predictive values Radiol Oncol 2022; 56(3): 390-397. Siuka D et al. / Abbreviated breath test 396 test in patients after subtotal and total gastrectomy. Two and half hours have been determined as opti- mal to detect patients with PEI with the cut-off val- ue of exhaled 13 C at 13.74% after 2.5 hours (Table 5). Ta king all that, there was also no difference in the required duration of the 13 C-MTGT breath test when comparing patients after total gastrectomy and the duration of the test in patients after sub- total gastrectomy, even though the transit time in the upper gastrointestinal tract depends on the type of gastrectomy and affects the time required for a breath test. Since the number of patients was small, no significant differences occurred, but with a larger number, we would expect a shorter duration time of the 13 C-MTGT breath test required when used in patients after total gastrectomy compared to subtotal gastrectomy patients. Our study was the first in this regard to perform the sub-analysis of patients with subtotal and total gastrectomy, and at the same time confirming shortening of the test. 16,17 Keller et al. in 2011 indicated that shortening the test to less than 6 hours, decreases the sensitivity, how- ever, even with considerable shorter sampling, the sensitivity and specificity ranged from 73% to 85% and 83% to 100%, respectively, and reached even higher sensitivity and specificity rates in mild to moderate PEI (100% and 92%, respectively). 17 They also showed that abbreviated version of the test was promising. Abbreviated test as such makes the examination more acceptable and comfortable in time, both for patients and medical staff. Our study contributes to the innovation in the diagnostics and treatment of patients with PEI after gastrectomy and improves their quality of life, as well as facili- tates the diagnostic process of these patients. This is important as in patients after gastrectomy, fecal elastase in the faeces may be preserved and the sen- sitivity of this test is expected to be low because the mechanism of PEI is extrapancreatic. 18,19 Therefore, there is a presence of the risk that patients may be deprived of appropriate treatment with pancreatic enzyme replacement therapy (PERT). 4 Because PEI has a strong impact on quality of life, additional tests such as 13 C-MTGT breath test in addition to Fe-1 or 13 C-MTGT breath test on its own detects more patients. Meanwhile the 13 C-MTGT breath test is a non-invasive test that indirectly assesses pancreatic l ipase activity and pancreatic exocrine, detects levels of undigested or digested products following gastric resection, so it is appropriate for patients after gastrectomy. 11-14,18,20 Other trials have also tested patients with suspected PEI who under- went a modified shortened 13 C-MTGT breath test, but some did not include patients after gastrecto- my. 15-17 On the other hand, they demonstrated high sensitivity for severe PEI ranging 90% to 100% and specificity ranging 80% to 90%. 4,17,21 Our data are though in concordance with these results. The current study showed that our abbrevi- ated version of the 13 C-MTGT after 2.5 hours shows valuable diagnostic power. Both sensitivity and specificity exceeded 90% which represent a strong performance and importantly, after 2.5 hours might detect almost all patients with moderate or severe PEI. Similar performance was observed by Keller et al. in two of their previous research with similar cut-off value but rather after 4 hours. 13,14 The findings of all studies suggested that for clini- cal purposes the testing period may be shortened. Keller et al. performed their study in 181 patients and revealed that cumulative 13 C-exhalation with 13 C-MTGT breath test over 4 hours had 88% sensi- tivity and 94% specificity for detection of PEI when compared to the standard 6-hour test. 17 This reli- ability has been previously confirmed. 16 Thus, the evaluation of pancreatic exocrine function using abbreviated test was in concordance with several studies showing that the abbreviated test might be of diagnostic value and used in clinical practice. 16,17 However, due to different optimal timepoint more studies need to be evaluated confirming the exact time point for determine PEI as previous studies showed only minor abbreviation when compared to our data showing the abbreviation of more than 3 hours. Nevertheless, our findings are significant for bringing innovation into clinical practice and the study design encompassed two groups of patients FIGURE 1. Receiver operating characteristic (ROC) curves for respective time points of breathing test for all subjects. NPV = negative predictive values; PPV = positive predictive values; Sens = sensitivity; Spec = specificity Radiol Oncol 2022; 56(3): 390-397. Siuka D et al. / Abbreviated breath test 397 that might develop PEI, our analysis had limita- tions. The sample size that was used is relatively small. Out of 65 subjects, only 22 had PEI. Se condly, the patients were not split by the surgical proce- dure. They had undergone the Roux-en-Y method or the Billroth I (BI) and the types might be associ- ated with differences in fat digestive and absorp- tive function as BI reconstruction was proven to be superior to that after Roux-en-Y reconstruction. 13 Furthermore, the basic characteristics of healthy controls did not match in age with patients’ group. Here it must be highlighted that the controls were used only as a baseline group stimulating statisti- cal power of PPV and NPV in subjects. The testing time was not compared to other treatment modali- ties and possible diet was not evaluated to impact the testing results. Finally, in our study gastric emptying was not performed so its influence on the duration of the test or on the rates of abbrevi- ated 13 C-exhalation was not covered, despite that gastric emptying parameter was proven similar in patients and controls, and correction for these did not improve accuracy of 13 C-MTGT. 13 On e of the limitations was also not regarding the possible con- comitant adjuvant/ neoadjuvant chemotherapy. The importance of our study is that it demon- strated the possibility of shortening the 13 C-MTGT breath test for patients after total and subtotal gas- trectomy, which may make the test less time con- suming and therefore more patient-friendly and medical stuff-friendly and suitable for wider clini- cal use in these two groups of patients for the as- sessment of PEI. Conclusions The negative side of the breath test for detection of PEI is the long 5-hour procedure, which is burden- some for patients and medical personnel. Because of this there is a great clinical need for the test to be shortened. In the study we confirmed that this can be performed in a subgroup of patients with re- sected stomach due to gastric cancer. The abbrevi- ated 13 C-MTGT breath test to 2.5 hours performed equally as the standard 5-hour test in this subgroup of patients. The results of study support the use of abbreviated test in patients after gastrectomy. 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