Given a passage with a context and an answer, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.

Input: Consider Input: Context: Thailand has the lowest incidence of gastric cancer in the world. Helicobacter pylori infection, a low serum pepsinogen I/II ratio, and interleukin (IL)-1beta-511 polymorphisms are suspected to be risk factors for gastric cancer.', 'A total of 167 Thais, comprising 56 cancer patients and 111 volunteers without cancer, underwent an esophagogastroduodenoscopic examination and three fixed-point biopsies; a cancer tissue biopsy was also done, and blood samples were collected. The subjects without cancer were divided into normal subjects and chronic gastritis patients. IL-1beta-511 polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism, and the serum levels of pepsinogen I and II were determined by a radioimmunoassay. Helicobacter pylori IgG antibody and tissue pathology were tested in all groups.', 'The pepsinogen I/II ratio was significantly lower in the gastric cancer group than in the normal and chronic gastritis groups [odds ratio (OR), 2.3; 95% confidence interval (CI), 1.10-4.80; P = 0.025]. Gastric cancer patients were positive for the H. pylori IgG antibody more frequently than negative (OR, 2.946; 95% CI, 1.4-6.39; P = 0.005). However, only 15 (27%) cancer patients were both positive for H. pylori IgG antibody and had low serum pepsinogen I/II. The C/C genotype was found more frequently in the gastric cancer group than in the group with a normal gastric mucosa (OR, 0.64; 95% CI, 0.50-0.81; P = 0.014).
Answer: A low serum pepsinogen I/II ratio combined with positivity for H. pylori IgG, and a IL-1beta-511 C/C genotype may be independent risk factors for gastric cancer in Thais.

Output: Are helicobacter pylori infection in combination with the serum pepsinogen I/II ratio and interleukin-1beta-511 polymorphisms independent risk factors for gastric cancer in Thais?


Input: Consider Input: Context: Before desflurane is advocated for patients undergoing neurosurgical procedures, it is necessary to determine the effect of desflurane on cerebral blood flow (CBF). In this study, CBF values are compared between desflurane and isoflurane at two doses. In addition, CBF reactivity to CO2 and the effect of prolonged exposure were compared between the two agents.', 'Cerebral blood flow measurements with intravenous 133Xe were performed in 24 patients undergoing craniotomy for mass lesions, randomized to receive either isoflurane or desflurane in oxygen and air. Cerebral blood flow was determined at 1 and 1.5 MAC concentrations at PaCO2 of 25 mmHg in the absence of surgical stimulation. Intraoperatively, with 1.25 MAC anesthesia, CBF was determined at target PaCO2 of 25 and 35 mmHg. In 15 patients, an additional measurement at 1.25 MAC was made before closure.', 'At 1.0 MAC, mean +/- SD CBF values for the desflurane and isoflurane groups were 18 +/- 2 and 20 +/- 3 ml x 100 g-1 x min-1, respectively. At 1.5 MAC, CBF values were the same for the two anesthetics; 17 +/- 3 ml x 100 g-1 x min-1 for isoflurane and 19 +/- 4 ml.100 g-1 x min-1 for desflurane. During 1.25 MAC anesthesia, there were no differences between groups, with CO2 reactivity 1.3 +/- 1.2 ml x 100 g-1 x min-1 x mmHg-1 for desflurane and 1.6 +/- 0.6 ml.100 g-1 x min-1 x mmHg-1 for isoflurane. There was no demonstrable decrease in CBF with prolonged exposure to either agent.
Answer: Desflurane and isoflurane are similar in terms of absolute CBF, the response to increasing doses, and the preservation of CO2 reactivity.

Output: Do desflurane and isoflurane have similar effects on cerebral blood flow in patients with intracranial mass lesions?


Input: Consider Input: Context: Coronary artery calcium (CAC) is a powerful CAD risk marker when assessed by dedicated calcium scoring CT scan. We assessed diagnostic implications of CAC visible on attenuation correction CT scans (CTAC) from SPECT/CT myocardial perfusion imaging (MPI).', 'Visual presence or absence of CAC was assessed on CTAC in 1047 consecutive patients undergoing SPECT/CT MPI. Accuracy of MPI was assessed in patients undergoing invasive coronary angiography (ICA) within 1\xa0year (n\xa0=\xa0109). Outcomes were identified by retrospective chart review.', 'Prevalence of true positive SPECT/CT MPI studies was greater among patients with CAC on CTAC (70% vs 16%; p\xa0<\xa0.001); prevalence of false positive studies was greater among those without (68% vs 15%; p\xa0<\xa0.001). PPV of MPI was 0.82 in patients with CAC, but only 0.19 in those without. Within median follow-up of 27.7\xa0months, patients with CAC had higher all-cause mortality (6% vs 0.4%; p\xa0<\xa0.001), more late revascularizations (8% vs 0.4%; p\xa0<\xa0.001), and more MI (5% vs 0.2%; p\xa0<\xa0.001). Hazard ratio for all-cause mortality, MI, or late revascularization was 22.7 (p\xa0<\xa0.001) for patients with CAC vs those without.
Answer: Visual assessment of CAC on CTAC should be performed during SPECT/CT MPI because it affects diagnostic certainty and may improve risk stratification.


Output: Does visual identification of coronary calcifications on attenuation correction CT improve diagnostic accuracy of SPECT/CT myocardial perfusion imaging?