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Purpose We investigated the correlation between the number of examined lymph nodes (ELNs) and correct staging and long-term survival in non-small-cell lung cancer (NSCLC) by using large databases and determined the minimal threshold for the ELN count. Methods Data from a Chinese multi-institutional registry and the US SEER database on stage I to IIIA resected NSCLC (2001 to 2008) were analyzed for the relationship between the ELN count and stage migration and overall survival (OS) by using multivariable models. The series of the mean positive LNs, odds ratios (ORs), and hazard ratios (HRs) were fitted with a LOWESS smoother, and the structural break points were determined by Chow test. The selected cut point was validated with the SEER 2009 cohort. Results Although the distribution of ELN count differed between the Chinese registry (n = 5,706) and the SEER database (n = 38,806; median, 15 versus seven, respectively), both cohorts exhibited significantly proportional increases from N0 to N1 and N2 disease (SEER OR, 1.038; China OR, 1.012; both P < .001) and serial improvements in OS (N0 disease: SEER HR, 0.986; China HR, 0.981; both P < .001; N1 and N2 disease: SEER HR, 0.989; China HR, 0.984; both P < .001) as the ELN count increased after controlling for confounders. Cut point analysis showed a threshold ELN count of 16 in patients with declared node-negative disease, which were examined in the derivation cohorts (SEER 2001 to 2008 HR, 0.830; China HR, 0.738) and validated in the SEER 2009 cohort (HR, 0.837). Conclusion A greater number of ELNs is associated with more-accurate node staging and better long-term survival of resected NSCLC. We recommend 16 ELNs as the cut point for evaluating the quality of LN examination or prognostic stratification postoperatively for patients with declared node-negative disease.

BACKGROUND: Testing stimulates learning, improves long-term retention, and promotes technical performance. No purpose-orientated test of competence in the theoretical aspects of VATS lobectomy has previously been presented. The purpose of this study was, therefore, to develop and gather validity evidence for a theoretical test on VATS lobectomy consisting of multiple-choice questions.METHODS: Four European VATS lobectomy experts were interviewed to explore their views on important theoretical VATS lobectomy knowledge (step 1). This information was used to construct the test items in compliance with existing guidelines for multiple-choice questions (step 2). The experts rated the relevance of the items to confirm content validity in a modified Delphi approach (step 3). Finally, the test was administered to physicians, who were categorised into different experience levels based on their experience in VATS procedures overall and in VATS lobectomies specifically. Their answers were used to achieve construct validity (step 4).RESULTS: Initially, 81 items were constructed and two Delphi iterations reduced the test to 50 items. Item analysis led to the exclusion of 19 items and the mean discrimination index of the 31 final items was 0.26. Cronbach's alpha for internal consistency was 0.75. The mean item difficulty was calculated to 0.63. According to performed VATS procedures, significantly different test performances were detected when comparing the group performances (p = 0.002) and the experts performed significantly better than the novices (p < 0.001) and intermediates (p = 0.01). In the category of performed VATS lobectomies, significant group performances were also found. In this category, the experts were also significantly better than the novices (p < 0.001), the trainees (p = 0.002), and the intermediates (p = 0.01).CONCLUSIONS: This study led to the development of a theoretical test on VATS lobectomy consisting of multiple-choice que