Common use of Study Population Clause in Contracts

Study Population. All patients who underwent elective surgery with primary anastomosis creation for a first primary colon carcinoma between January the 1, 2013 and December the 31, 2019, and registered in the DCRA were potentially eligible. Data extracted from the DCRA comprised characteristics concerning patient, tumor, surgical and follow−up information. The 30−day follow−up was registered until December 31, 2017, and from January 1, 2018, the 90−day follow−up was registered. Index surgical procedures were divided into right hemicolectomy, transversectomy, left hemicolectomy, sigmoid resection, and subtotal colectomy. AL was defined as a defect of the intestinal wall or abscess at the site of the colorectal anastomosis, for which a reintervention was required within 30 to 90−days from primary resection. Since the date of AL diagnosis is not available in the DCRA, the present study reports the follow−up from index colectomy to reintervention. Reinterventions were divided into two categories: (1) surgical reinterventions including laparoscopic and open surgical reinterventions, and (2) non−surgical reinterventions including radiologic−, endoscopic−, and other unspecified reinterventions. For each type of index colectomy, the occurrence of AL, type of reintervention, and timing of reintervention were determined. Primary outcomes after reoperation were mortality, ICU admission, and stoma construction. Secondary outcomes were prolonged hospital stay (primary admission of >14 days after index procedure), readmission, stoma creation per type (defunctioning ileo or colostomy, end ileo or colostomy), and mortality for patients with and without stoma creation during reoperation. Baseline study population characteristics are reported for patients with and without AL. Outcomes after reoperation were reported for the total study population and for each type of index colectomy. Sub−analyses were performed to assess differences in outcomes for reoperation performed during the weekend vs. week and for different annual hospital volumes. Since the Dutch standard states that hospitals should perform at least 50 colonic resections per year,19 volumes were categorized into low− (<50), low−intermediate (50−75), intermediate−high (76−100), and high (>100 ) volume hospitals. Categorical and dichotomous variables are reported as absolute numbers with percentages and were compared using the Xxxxxxx Xxx−square test or Xxxxxx−Exact test. Continuous variables are reported as median with interquartile range (IQR), and a Kruskal Wallis rank−sum test was used to assess statistical significance. The time interval between surgery and reoperation was calculated using the date of surgery and the date of reintervention. To visualize the timing of reoperation, the number of reoperations per two days was plotted for each type of resection separately. Statistical significance was defined as a p-value <0.05. RStudio version 1.4.1106 (2021) was used for statistical analyses.