Predicting gender differences as latent variables: summed scores, and individual item responses: a methods case study

BACKGROUND: Modeling latent variables such as physical disability is challenging since its measurement is performed through proxies. This poses significant methodological challenges. The objective of this article is to present three different methods to predict latent variables based on classical summed scores, individual item responses, and latent variable models. METHODS: This is a review of the literature and data analysis using "layers of information". Data was collected from the North Carolina Back Pain Project, using a modified version of the Roland Questionnaire. RESULTS: The three models are compared in relation to their goals and underlying concepts, previous clinical applications, data requirements, statistical theory, and practical applications. Initial linear regression models demonstrated a difference in disability between genders of 1.32 points (95% CI 0.65, 2.00) on a scale from 0–23. Subsequent item analysis found contradictory results across items, with no clear pattern. Finally, IRT models demonstrated three items were demonstrated to present differential item functioning. After these items were removed, the difference between genders was reduced to 0.78 points (95% CI, -0.99, 1.23). These results were shown to be robust with re-sampling methods. CONCLUSIONS: Purported differences in the levels of a latent variable should be tested using different models to verify whether these differences are real or simply distorted by model assumptions

DADOS-Prospective: an open source application for Web-based prospective data collection

BACKGROUND: Randomized, prospective trials involving multi-institutional collaboration have become a central part of clinical and translational research. However, data management and coordination of multi-center studies is a complex process that involves developing systems for data collection and quality control, tracking data queries and resolutions, as well as developing communication procedures. We describe DADOS-Prospective, an open-source Web-based application for collecting and managing prospective data on human subjects for clinical and translational trials. DADOS-Prospective not only permits users to create new clinical research forms (CRF) and supports electronic signatures, but also offers the advantage of containing, in a single environment, raw research data in downloadable spreadsheet format, source documentation and regulatory files stored in PDF format, and audit trails. RESULTS: Feedback from formal and field usability tests was used to guide the design and development of DADOS-Prospective. To date, DADOS-Prospective has been implemented in five prospective clinical studies at our institution. Four of these studies are still in the CRF creation phase and one study has been entirely launched. CONCLUSION: DADOS-Prospective has significant advantages over existing Web-based data collecting programs. At our institution, it has been demonstrated to be an efficient tool for prospective clinical studies

Laparoscopic Appendectomy Outcomes on the Weekend and During the Week are no Different: A National Study of 151,774 Patients

Background: The "weekend effect” is defined as increased morbidity and mortality for patients admitted on weekends compared with weekdays. It has been observed for several diseases, including myocardial infarction and renal insufficiency; however, it has not yet been investigated for laparoscopic appendectomy in acute appendicitis—one of the most prevalent surgical diagnoses. Methods: The present study is based on the Nationwide Inpatient Sample (NIS) from 1999 to 2008. The following outcomes were compared between patients undergoing laparoscopic appendectomy for acute appendicitis admitted on weekdays versus weekends: severity of appendicitis, intraoperative and postoperative complications, conversion rate, in-hospital mortality, and length of hospital stay. Unadjusted and risk-adjusted generalized linear regression analyses were performed. Results: Overall, 151,774 patients were included, mean age was 39.6years, 52.6% (n=79,801) were male, and 25.3% (n=38,317) were admitted on weekends. After risk adjustment, the conversion rate was lower [odds ratio (OR): 0.94, p=0.004, number needed to harm (NNH): 244], whereas pulmonary complications (OR: 1.12, p=0.028, NNH: 649) and reoperations (OR: 1.21, p=0.013, NNH: 1,028) were slightly higher on weekends than on weekdays. Overall postoperative complications (OR: 1.03, p=0.24), mortality (OR: 1.37, p=0.075) and length of hospital stay (mean on weekday: 2.00days, weekends: 2.01days, p=0.29) were not statistically different. Conclusions: The present investigation provides evidence that no clinically significant "weekend effect” for patients undergoing laparoscopic appendectomy exists. Therefore, hospital or staffing policy changes are not justified based on the findings from this large national stud