Bluemel S, Menne D, Fried M, Schwizer W, Steingoetter A
Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland.
Menne Biomed Consulting, Tübingen, Germany.
Neurogastroenterol Motil. 2015 Oct;27(10):1487-94. doi: 10.1111/nmo.12648. Epub 2015 Aug 12.
(13) C-acetate breath testing (BT) is applied to assess and compare gastric emptying of liquid meals. Gastric half-emptying times (t50 ) from BT show offsets compared to t50 values from γ-scintigraphy and ultrasonography. Linear transformations have been proposed to correct these offsets. This investigation critically validates the BT for the assessment of liquid gastric emptying by using simultaneously recorded meal and total gastric content volume emptying data from magnetic resonance imaging (MRI).
Data were collected during a recently published double-blind, randomized, cross-over MRI gastric emptying study of three (13) C-labeled enteral formulas differing in protein sources (PMID: 24699556). Breath testing-derived t50 was computed with the analysis methods commonly applied in gastric emptying research, i.e., the exponential-beta function and the Wagner-Nelson (WN) method, respectively.
Breath testing t50 values from exponential-beta function and WN method showed a positive and negative offset to MRI data, respectively. Linear regression detected low concordance between MRI and both BT methods revealing meal specific and emptying rate-dependent offsets. The WN method showed worse agreement and correlation with MRI emptying data. Breath testing rather reflected meal volume than total gastric content volume emptying.
CONCLUSIONS & INFERENCES: This validation study indicates that the (13) C-acetate breath test may not be applied to compare gastric emptying of arbitrary liquid meals without prior validation by imaging methods. t50 values from BT are biased by (i) the properties of the meal and (ii) the selected method used for (13) CO2 exhalation analysis. No linear transformation common for all meals was applicable to correct the offsets between BT and MRI.
¹³C - 醋酸呼气试验(BT)用于评估和比较流食的胃排空情况。与γ闪烁扫描法和超声检查法测得的胃半排空时间(t50)相比,BT测得的t50存在偏差。有人提出用线性变换来校正这些偏差。本研究通过同时记录磁共振成像(MRI)的餐食和胃内容物总体积排空数据,对BT评估液体胃排空的有效性进行了严格验证。
数据收集自最近发表的一项双盲、随机、交叉MRI胃排空研究,该研究涉及三种蛋白质来源不同的¹³C标记肠内配方食品( PMID:24699556)。分别采用胃排空研究中常用的分析方法,即指数 - β函数法和瓦格纳 - 尼尔森(WN)法,计算呼气试验得出的t50。
指数 - β函数法和WN法测得的呼气试验t50值分别与MRI数据存在正向和负向偏差。线性回归显示MRI与两种BT方法之间的一致性较低,表明存在餐食特异性和排空率依赖性偏差。WN法与MRI排空数据的一致性和相关性较差。呼气试验更多反映的是餐食体积而非胃内容物总体积排空情况。
本验证研究表明,在未经成像方法预先验证的情况下,¹³C - 醋酸呼气试验可能不适用于比较任意流食的胃排空情况。BT测得的t50值受以下因素影响:(i)餐食的特性;(ii)用于¹³CO₂呼出分析的所选方法。不存在适用于所有餐食的通用线性变换来校正BT与MRI之间的偏差。