www.revhipertension.com Revista Latinoamericana de Hipertensión. Vol. 14 - Nº 1, 2019 The effect of warming specimens of rapid urease test on its diagnostic accuracy El efecto del calentamiento de las muestras de la prueba de ureasa rápida en su precisión diagnóstica 15 Jafar Nasiri1*, https://orcid.org/0000-0003-3624-6849, Arshya Allahdin2, https://orcid.org/0000-0002-7370-9227, Reza Imani3, https://orcid.org/0000-0001-8149-9349, Soleiman Kheiri4, https://orcid.org/0000-0001-8285-8681, Abolfazl Khoshdel 5https://orcid.org/0000-0002-7023-5951 1Gastroenterologist, Assistant Professor, Department of Internal Medicine, Faculty of Medicine, Shaharekord University of Medical Sciences, Shahrekord, Iran 2Assistant of Pathology, Department of Pathology, Faculty of Medicine, Jundishapour Medical Sciences University, Ahwaz, Iran 3Associate Professor, Department of Infectious Diseases, Shahrekord University of Medical Sciences, Shahrekord, Iran 4Associate Professor, Department of Epidemiology and Biostatistics, Faculty of Health, Shahrekord University of Medical Sciences, Shahrekord, Iran 5Associate Professor, Department of Pediatrics, Faculty of Medicine, Shahrekord University of Medical Sciences, Shahrekord, Iran *corresponding author: Jafar Nasiri, Gastroenterologist, Assistant Professor, Department of Internal Medicine, Faculty of Medicine, Shaharekord University of Medical Sciences, hahrekord, Iran, Postal address: Department of Internal Medicine, Shaharekord University of Medical Sciences, Shahrekord, Iran, Postal code: 88157-13471, Tel: +9838- 32223350. Fax: +9838-32243715. Email: [email protected] Introduction: Helicobacter pylori (H. pylori) is a prevalent opsy was placed in formalin solution; one tube was placed cause of dyspepsia, peptic ulcer and gastric cancer in de- in incubator with 37oC and the other at room tempera- veloping countries. Among various diagnostic methods, ture (22-25oC). Positivity of RUT test at different times was rapid urease test (RUT) is the ideal test for its diagnosis compared to histopathological examination. Abstract in patients undergoing endoscopy. Studies have identi- fied the factors causing false negative and positive results. Results: Infection with Helicobacter pylori was confirmed One of these factors is proposed to be the temperature of by histological examination in 66% of patients. After 24 o keeping specimens, but the results have been controver- hours, sensitivity of incubated RUT was 71% at 37 C, and o sial. We aimed to compare the diagnostic accuracy of RUT 68% at room temperature (P=0.85). Specificity at 37 C specimens warmed at 37oC or kept at room temperature was 59% and at room temperature was 76% (P=0.19). o (22-25oC) in different time intervals until 24 hours. Median time to positive tests was 2 hours at 37 C and 3 hours at room temperature, while RUT became positive o Methods: 100 patients with dyspepsia who were indi- faster at 37 C (P=0.553). cated for endoscopic examination were selected based on Conclusion: The non-significant difference between convenience sampling method from patients referring to groups revealed that warming could not improve the Endoscopy center of Hajar Hospital during August-Sep- diagnostic accuracy of RUT test, thus, the standard RUT tember 2006. After recording the demographic and medi- method is recommended. cal history of patients, three biopsy specimens were taken from one portion of the antrum; the first two samples Keywords: Helicobacter pylori; Diagnostic Tests, Routine; were placed in home-made RUT solution and the third bi- Endoscopy, Gastrointestinal; Urease. Introducción: Helicobacter pylori (H. Pylori) es una causa Métodos: se seleccionaron 100 pacientes con dispepsia frecuente de dispepsia, úlcera péptica y cáncer gástrico que estaban indicados para un examen endoscópico según en países en desarrollo. Entre los diversos métodos de di- el método de muestreo de conveniencia de los pacientes agnóstico, la prueba rápida de ureasa (RUT) es la prueba que se referían al centro de Endoscopia del Hospital Hajar ideal para su diagnóstico en pacientes sometidos a en- entre agosto y septiembre de 2006. Después de registrar la Resumen doscopia. Los estudios han identificado los factores que historia demográfica y médica de los pacientes, se tomaron causan resultados falsos negativos y positivos. Se propone tres muestras de biopsia. Una porción del antro; las dos que uno de estos factores es la temperatura para con- primeras muestras se colocaron en una solución de RUT servar las muestras, pero los resultados han sido contro- hecha en casa y la tercera biopsia se colocó en una solu- vertidos. El objetivo fue comparar la precisión diagnóstica ción de formalina; un tubo se colocó en una incubadora de las muestras RUT calentadas a 37°C o mantenidas a con 37°C y el otro a temperatura ambiente (22-25°C). La temperatura ambiente (22-25°C) en diferentes intervalos positividad de la prueba de RUT en diferentes momentos se de tiempo hasta 24 horas. comparó con el examen histopatológico. Resultados: la infección con Helicobacter pylori se con- bacteria to change color in an agar-based like CLO test firmó mediante examen histológico en el 66% de los (campylobacter–like organism) and has high sensitivity pacientes. Después de 24 horas, la sensibilidad del RUT varying from 80-100% and specificity of 97-100%, based incubado fue del 71% a 37°C y del 68% a temperatura on the methods and techniques used8. Obtaining two ambiente (P=0,85). La especificidad a 37°C fue del 59% y samples from antrum can result in a sensitivity of 95% la temperatura ambiente fue del 76% (P=0.19). El tiempo and specificity of 100%9. In addition, although most spec- medio para las pruebas positivas fue de 2 horas a 37°C y imens turn positive in the first 120-180 minutes, investi- 3 horas a temperatura ambiente, mientras que el RUT se gation of specimens for 24 hours and no longer results in convirtió en positivo más rápido a 37°C (P=0.553). most accurate detection of H. Pylori bacteria8. Conclusión: la diferencia no significativa entre los grupos Studies have investigated other factors that play a role in reveló que el calentamiento no podría mejorar la precisión diagnostic accuracy of RUT; some have suggested that us- diagnóstica de la prueba RUT, por lo que se recomienda el ing proton pump inhibitors (PPI) by the patient reduces its método RUT estándar. sensitivity and increases false negative results10. Moreover, 16 other bacterial species may rarely cause false positive11. Palabras clave: Helicobacter pylori; Pruebas de diagnós- Some studies have also advised that the temperature of tico, de rutina; Endoscopia gastrointestinal; Urease. reaction might influence the diagnostic value of RUT; some researchers suggested that using a warmer with 38oC had a 20% higher diagnostic ability in the first 30 minutes, while overall results did not differ significantly12, while other researchers proposed that warming the speci- mens at 37oC increased the sensitivity of RUT until 2 hours and had an earlier mean time to positive test13. elicobacter pylori (H. pylori) is a gram- Due to the significance of RUT in diagnosis of H. pylori, Introduction negative bacterium that affects a large beside the controversial results regarding the effect of number of patients worldwide, with a temperature on diagnostic accuracy of RUT, the present significantly high prevalence in developing countries and study aimed to evaluate the diagnostic accuracy of RUT, low socio-economic communities, although its prevalence in specimens kept at 37oC, compare with specimens kept differs by age, sex, race, and other factors1. H. pylori in- at room temperature in different intervals until 24 hours. fection is reported to have a high prevalence in Iran with a prevalence of more than 80% reported in many cities2. H. pylori infection is of great importance, as it leads to chronic gastritis, peptic ulcer disease, gastric cancer and mucosa-associated lymphoid-tissue (MALT) lymphoma3. The age-standardized risk of gastric cancer varies from 10.2 to 50 per 100,000 person-year in different cities2. Therefore, H. pylori infection requires early and accurate diagnosis4. tudy design: In this prospective study, 100 patients (including 50 males and 50 females) Although international guidelines suggest endoscopy af- with dyspepsia who were indicated for en- Materials and methods ter empirical acid suppression, it is suggested that this ap- doscopic evaluation were selected based on convenience proach, named as “test and treat”, is not beneficial in sampling method among patients referring to Endoscopy countries with high prevalence of H. pylori infection5, like center of Hajar Hospital from July to September 2006. Iran, and endoscopic-based methods are recommended Sample size was calculated to estimate the sensitivity and for eradication of H. pylori infection4. specificity of RUT with the 10% precision and 95% confi- dence, using the overall sensitivity/specificity equal to 50%. Although none of the various methods suggested have been proven as the gold standard, studies have suggested Patients with dyspepsia aged over 14 years who were re- various invasive and noninvasive methods for diagnosis of ferred to Endoscopy center of Hajar Hospital from July to H. pylori infection: non-invasive methods include serol- September 2006 were included into the study. Any patient ogy, immunoblot, stool antigen test, and urea breath test with recent gastrointestinal bleeding, and urgent cases (UBT), and invasive tests include, histologic examination