External comparisons with the case-cohort design

The case-cohort design can be an economic alternative to the standard cohort design. Prentice (Biometrika 1986;73:1-11) showed how the case-cohort design can be used to obtain relative risk estimates for comparisons within the cohort being studied. In this paper, the authors consider ways in which the case-cohort design can be used for comparing risk in exposure groups within the cohort to the risk in an external population. The problem reduces to estimating the number of expected cases at each exposure level in the total cohort, when exposure status is available only for members of a subcohort, i.e., a random sample of the total cohort. The authors describe theoretical and empirical properties of several variations of the design and analysis of case-cohort studies. Empirical properties were examined by replicating the selection of the subcohort in a study of second cancer risk after chemotherapy for a first cancer. Use of a case-cohort design in that study would have saved five-sixths of the cost of gathering covariate information at the price of only an 11% loss in efficiency relative to a full cohort study.     

Is Coronary Graft Doppler More Sensitive for Indiviual Graft Flows Than TEE During CABG Surgery?

Abstract    In this case report we describe a situation where despite a normal TEE exam immediately postcardiopulmonary bypass, there was no flow in the left internal mammary artery graft to the left anterior descending artery. This was picked up by coronary Doppler and subsequently repaired.     

Determination of the risk of a 2d cancer in patients treated for a first cancer

A paradoxical effect of radiotherapy and chemotherapy for cancer is that some of these treatments can themselves cause new cancers. Most epidemiologic methods can be applied successfully to the investigation of this problem and this paper reviews various approaches that have already been used by various researchers. The authors first review the more traditional methods, i.e., cohort and case-control studies and they then describe designs that have been proposed more recently, such as case-cohort studies. A distinction is established between internal comparisons, carried out within the study population, and external comparisons, in which a general population external to the population under study is used as the reference category. This presentation is mainly aimed at investigators using tumor registry data. However, the general principles formulated here are easily generalized to contexts other than that of registries.     

Comparison of bone mass measured by histomorphometry on iliac biopsy and by dual photon absorptiometry of the lumbar spine

In a prospective study we compared bone mass measured independently by dual photon absorptiometry (DPA) on lumbar spine and by histomorphometry on transiliac biopsy. Measurements were done in 83 patients (23 males, 60 females) with various generalized bone diseases, including spinal osteoporosis, primary hyperparathyroidism and osteopetrosis. Iliac bone density was analyzed on bone biopsy with an automatic image analyzer and expressed as the trabecular bone volume (TBV), the cortical thickness (CT) and the total bone density (TBD) which includes the density of both spongy and cortical bone within the periosteal envelope. The bone mineral content (BMC) and density (BMD) were measured from L2 to L4 with a Novo Lab 22a device. For the 83 patients, there were significant correlations between values given by both methods, with r values ranging from 0.74 to 0.43, according to the bone mass parameters analyzed. In the 37 patients with untreated vertebral osteoporosis, the TBV--but not the CT nor the TBD--correlated significantly with the BMD of the spine (r = 0.53, p less than 0.001). In conclusion, there is a significant correlation between bone density of the iliac crest assessed histomorphometrically and spinal density measured by DPA. Despite the fact that DPA measures both trabecular and cortical bone of the spine, it correlates better with iliac trabecular bone mass than with the overall iliac bone density.     

The effect of total arterial grafting on medium-term outcomes following coronary artery bypass grafting

Background  

While it is believed that total arterial grafting (TAG) for coronary artery bypass grafting (CABG) confers improved long-term outcomes when compared to conventional grafting with left internal mammary artery and saphenous vein grafts (LIMA+SVG), to date, this has not become the standard of care. In this study, we assessed the impact of TAG on medium-term outcomes after CABG.     

Incidence and Management of Chyle Leaks Following Pancreatic Resection: A High Volume Single-Center Institutional Experience

Background   No data on incidence, management, or natural history of chyle leaks following pancreatic resection have been published. We sought to identify possible risk factors associated with chyle leaks following pancreatic resection, as well as determine the natural history of this rare complication. Methods   Between 1993 and 2008, 3,532 patients underwent pancreatic resection at a single institution. Data on demographics, operative details, primary tumor status, and chyle leak were collected. To identify risk factors associated with chyle leak, a matched 3:1 paired analysis was performed. Results   Of 3,532 patients undergoing pancreatic resection, 47 (1.3%) developed a chyle leak (n = 34, contained chyle leak versus n = 13, diffuse chylous ascites). Chyle leak was identified at median 5 days following surgery. Median drain triglyceride levels were 592 ng/dl. After matching on tumor size, disease etiology, and resection type, the number of lymph nodes harvested and history of concomitant vascular resection predicted higher risk of chyle leak (both P < 0.05). Total parenteral nutrition (TPN) was required in more patients with chylous ascites (92.3%) than those with chyle leaks (44.1%) (P = 0.003). The median time to resolution was shorter for contained chyle leaks (13 days) versus chylous ascites (36 days) (P < 0.001). Patients with chylous ascites tended to have shorter overall survival (3-year, 18.8%) versus patients with no chyle leak (3-year, 46.9%) (P = 0.12). In contrast, patients with a contained chyle leak had a similar survival as patients with no chyle leak (3-year, 53.4% versus 46.9%, respectively) (P = 0.32). Conclusion   Chyle leak was a rare (1.3%) complication following pancreatic resection that was associated with number of lymph nodes harvested and concomitant vascular resection. In general, chyle leaks were successfully managed with TPN with no adverse impact on outcome. Patients with chylous ascites, however, had a more protracted clinical course and tended to have a worse long-term survival. Presented at the Society for Surgery of the Alimentary Tract, 49th Annual Meeting, San Diego, CA, May 18th, 2008 Support: Dr. Pawlik is supported by Grant Number 1KL2RR025006-01 from the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH), and NIH Roadmap for Medical Research. The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official view of NCRR or NIH.     

France: a focus on the new reproduction

This bibliographic essay's initial focus is on publications reflecting European concern with the ethical implications of reproductive technologies. Titles by P. Verspieren, the Institut Catholique de Lyon, C. Lefèvre, E. Loumaye and J-F. Malherbe, and J-L. Baudouin and C. Labrusse-Riou are briefly discussed. Also mentioned are recently published works on biomedical technologies by B. Edelman, M-A. Hermite, Labrusse-Riou, and M. Remond-Gouilloud; on the social impact of science by G. Hottois, J. DeVooght, R. Rasmont, and P. Van Gansen; on medical ethics by C. Ambroselli, and by Malherbe; on AIDS by E. Hirsch, by E. Conan, and by Malherbe and S. Zorrilla. All cited titles are in French.