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.

[EX Q]: Context: The aim of this study was to determine the clinical significance and prognostic impact of extranodal metastasis (EM) in gastric carcinoma.', 'The study included 1023 patients who underwent gastrectomy with lymphadenectomy for primary gastric carcinoma between January 1993 and December 1996. EM was defined as the presence of tumour cells in extramural soft tissue that was discontinuous with either the primary lesion or locoregional lymph nodes.', "EM was detected in 146 (14.3 per cent) of the 1023 patients and in 1060 (3.0 per cent) of the 35 811 nodules that were retrieved as 'lymph nodes' from adipose connective tissues. The incidence of EM was significantly higher in patients with tumours that were large (diameter 10 cm or more), infiltrative, deeply invading or undifferentiated and in those with lymph node, peritoneal or liver metastases, or lymphatic or vascular involvement. After curative operation overall survival was significantly worse for patients with EM than those without (P < 0.001). Multivariate analysis identified EM as an independent prognostic factor (hazard ratio 1.82 (95 per cent confidence interval 1.23 to 2.71); P = 0.003).
Answer: EM is an independent prognostic factor and should therefore be included in the tumour node metastasis (TNM) staging system.
[EX A]: Is extranodal metastasis an indicator of poor prognosis in patients with gastric carcinoma?

[EX Q]: Context: A new protocol for postoperative calcium management was developed with the aim of achieving an increase in the proportion of patients being safely discharged on the first postoperative day. We present our experience with the first 50 patients treated under this new protocol.', 'A cohort study was performed involving the first 50 patients admitted for total or completion thyroidectomy, those data were then compared with a control group. Intact PTH (iPTH) was measured at 4-h postoperatively and patients with iPTH in the normal range were discharged on the first postoperative day.', 'Mean age and sex distribution were similar in both groups. Mean lowest postoperative corrected calcium levels in the study group were 2.19 mmol/l and 2.15 mmol/l in the control group (P = 0.24). Parathyroid auto-transplantation was associated with low PTH levels (risk ratio = 0.49). Over 50% of patients (n = 27) were successfully discharged on the first postoperative day in the study group and no patient required readmission. Length of stay was significantly shorter in the study group, mean 1.64 vs. 2.20 days (P < 0.05).
Answer: The use of iPTH accurately predicts hypocalcaemia after total thyroidectomy and can be used to facilitate safe early discharge for patients.
[EX A]: Does postoperative PTH measurement facilitate day 1 discharge after total thyroidectomy?

[EX Q]: Context: Maraviroc (MVC) is a potential candidate for 'on demand' preexposure prophylaxis. In the present study, we evaluated the efficacy of a single oral dose of MVC to prevent ex-vivo HIV-1 infection of rectal tissue in humans.", 'Eight HIV-1-negative healthy volunteers received a single oral dose of MVC (300 or 600\u200amg), and two additional volunteers received tenofovir disoproxil fumarate/emtricitabine (TDF/FTC, 300/200\u200amg) for 10 days. Rectal biopsies were performed prior to the ex-vivo challenge (day 0), at day 7 (4\u200ah after MVC) or after 10 days with TDF/FTC. Rectal biopsies were infected ex-vivo, and viral inhibition and CCR5 occupancy was analyzed. MVC concentration in plasma and rectal tissue was measured just after biopsy and after viral incubation.', 'Ex-vivo rectal tissue protection with MVC was incomplete in all but two participants, whereas TDF/FTC avoided ex-vivo infection in the two controls. Median dose-normalized concentration of MVC was significantly higher in rectal tissue than in plasma (561.1 and 155.1\u200ang/ml, respectively). A significant loss of MVC during the virus incubation (about 60%) and a low CCR5 occupancy (approximately 45%) were detected in rectal cells.
Answer: An ex-vivo challenge with a single oral dose of MVC does not prevent ex-vivo infection of human rectal mucosa. The lack of prophylactic efficacy observed suggests that 'on demand' MVC preexposure prophylaxis would not prevent rectal HIV-1 transmission.
[EX A]:
Does single oral dose of maraviroc prevent ex-vivo HIV infection of rectal mucosa in HIV-1 negative human volunteers?