Graham D Y, Runke D, Anderson S Y, Malaty H M, Klein P D
Department of Medicine, Veterans Affairs Medical Center and Baylor College of Medicine, Houston, Texas 77030, USA.
Am J Gastroenterol. 1999 May;94(5):1214-7. doi: 10.1111/j.1572-0241.1999.01069.x.
Test meals are used in the urea breath test to slow gastric emptying and to increase the area of contact with the substrate. Recently, citric acid has been suggested as an improved liquid test meal. The mechanism is unknown and could act by delaying gastric emptying, decreasing the pH at the site of the bacteria, or both. Our aim was to evaluate the effects of citric acid test meals on urea hydrolysis in vivo, to identify the possible mechanism for enhanced urea hydrolysis, and to identify the minimum effective dose.
We compared the U.S. commercial 13C-urea breath test with four liquid test meals (200 ml of water) consisting of citric acid, ascorbic acid, sodium citrate, and glucose polymer and also after the subcutaneous administration of pentagastrin. We studied healthy volunteers with and without proven H. pylori infection (by serology and histology). 13C-urea was administered orally simultaneously with the liquid test meals or immediately after the pudding had been ingested. Breath samples were taken before and after oral administration of the 13C-urea.
A dose response in urease activity was evident as the amount of citric acid was increased from 1 to 4 g. Citric acid at 1, 2, or 4 g produced significant increases in breath 13CO2 activity, compared with the commercial pudding (p < 0.05). Ascorbic acid (p = 0.053), subcutaneous pentagastrin (to lower pH) (p = 0.199), and glucose polymer (p = 0.03) (to delay gastric emptying) all approximately doubled breath 13CO2, compared with the commercial kit. Nevertheless, the increases were all significantly less than with the 4 g citric acid test meal.
The data are consistent with the marked effect of citric acid on gastric emptying and, possibly, distribution of the urea within the stomach being largely responsible for the enhanced urease activity with citric acid test meals. It should be possible to use a low dose of citric acid (e.g., 1 g per 200 ml) to enhance the simplicity and palatability of the test.
在尿素呼气试验中使用试餐来减缓胃排空并增加与底物的接触面积。最近，柠檬酸被提议作为一种改良的液体试餐。其机制尚不清楚，可能是通过延迟胃排空、降低细菌所在部位的pH值，或两者兼而有之来起作用。我们的目的是评估柠檬酸试餐对体内尿素水解的影响，确定尿素水解增强的可能机制，并确定最小有效剂量。
我们将美国市售的13C尿素呼气试验与四种液体试餐（200毫升水）进行比较，这四种试餐分别由柠檬酸、抗坏血酸、柠檬酸钠和葡萄糖聚合物组成，并且在皮下注射五肽胃泌素后也进行了比较。我们研究了有和没有经证实的幽门螺杆菌感染（通过血清学和组织学）的健康志愿者。13C尿素在液体试餐同时口服，或在摄入布丁后立即口服。在口服13C尿素前后采集呼气样本。
随着柠檬酸量从1克增加到4克，脲酶活性呈现剂量反应。与市售布丁相比，1克、2克或4克柠檬酸使呼气中13CO2活性显著增加（p<0.05）。与市售试剂盒相比，抗坏血酸（p = 0.053）、皮下注射五肽胃泌素（降低pH值）（p = 0.199）和葡萄糖聚合物（p = 0.03）（延迟胃排空）均使呼气中13CO2增加约一倍。然而，这些增加均显著低于4克柠檬酸试餐。
数据表明柠檬酸对胃排空有显著影响，并且可能胃内尿素的分布在很大程度上导致了柠檬酸试餐脲酶活性增强。使用低剂量的柠檬酸（例如每200毫升1克）应该能够提高试验的简便性和适口性。
