University of Florence

About: University of Florence is a education organization based out in Florence, Toscana, Italy. It is known for research contribution in the topics: Population & Carbonic anhydrase. The organization has 27292 authors who have published 79599 publications receiving 2341684 citations. The organization is also known as: Università degli studi di Firenze & Universita degli studi di Firenze.

Robustness and sensitivity analysis of risk measurement procedures

Abstract: Measuring the risk of a financial portfolio involves two steps: estimating the loss distribution of the portfolio from available observations and computing a ‘risk measure’ that summarizes the risk of the portfolio. We define the notion of ‘risk measurement procedure’, which includes both of these steps, and introduce a rigorous framework for studying the robustness of risk measurement procedures and their sensitivity to changes in the data set. Our results point to a conflict between the subadditivity and robustness of risk measurement procedures and show that the same risk measure may exhibit quite different sensitivities depending on the estimation procedure used. Our results illustrate, in particular, that using recently proposed risk measures such as CVaR/expected shortfall leads to a less robust risk measurement procedure than historical Value-at-Risk. We also propose alternative risk measurement procedures that possess the robustness property.

Reliability of transient elastography for the diagnosis of advanced fibrosis in chronic hepatitis C

Abstract: Background: Transient elastography (TE) has received increasing attention as a means to evaluate disease progression in patients with chronic liver disease. Aim: To assess the value of TE for predicting the stage of fibrosis. Methods: Liver biopsy and TE were performed in 150 consecutive patients with chronic hepatitis C-related hepatitis (92 men and 58 women, age 50.6 (SD 12.5) years on the same day. Necro-inflammatory activity and the degree of steatosis at biopsy were also evaluated. Results: The areas under the curve for the prediction of significant fibrosis (>F2), advanced fibrosis (>F3) or cirrhosis were 0.91, 0.99 and 0.98, respectively. Calculation of multilevel likelihood ratios showed that values of TE , 6o r>12, , 9o r>12, and ,12 or >18, clearly indicated the absence or presence of significant fibrosis, advanced fibrosis, and cirrhosis, respectively. Intermediate values could not be reliably associated with the absence or presence of the target condition. The presence of inflammation significantly affected TE measurements in patients who did not have cirrhosis (p,0.0001), even after adjusting for the stage of fibrosis. Importantly, TE measurements were not influenced by the degree of steatosis. Conclusions: TE is more suitable for the identification of patients with advanced fibrosis than of those with cirrhosis or significant fibrosis. In patients in whom likelihood ratios are not optimal and do not provide a reliable indication of the disease stage, liver biopsy should be considered when clinically indicated. Necro-inflammatory activity, but not steatosis, strongly and independently influences TE measurement in patients who do not have cirrhosis.

Snapshot of Moving and Expanding Clones of Mycobacterium tuberculosis and Their Global Distribution Assessed by Spoligotyping in an International Study

Abstract: The present update on the global distribution of Mycobacterium tuberculosis complex spoligotypes provides both the octal and binary descriptions of the spoligotypes for M. tuberculosis complex, including Mycobacterium bovis, from >90 countries (13,008 patterns grouped into 813 shared types containing 11,708 isolates and 1,300 orphan patterns). A number of potential indices were developed to summarize the information on the biogeographical specificity of a given shared type, as well as its geographical spreading (matching code and spreading index, respectively). To facilitate the analysis of hundreds of spoligotypes each made up of a binary succession of 43 bits of information, a number of major and minor visual rules were also defined. A total of six major rules (A to F) with the precise description of the extra missing spacers (minor rules) were used to define 36 major clades (or families) of M. tuberculosis. Some major clades identified were the East African-Indian (EAI) clade, the Beijing clade, the Haarlem clade, the Latin American and Mediterranean (LAM) clade, the Central Asian (CAS) clade, a European clade of IS6110 low banders (X; highly prevalent in the United States and United Kingdom), and a widespread yet poorly defined clade (T). When the visual rules defined above were used for an automated labeling of the 813 shared types to define nine superfamilies of strains (Mycobacterium africanum, Beijing, M. bovis, EAI, CAS, T, Haarlem, X, and LAM), 96.9% of the shared types received a label, showing the potential for automated labeling of M. tuberculosis families in well-defined phylogeographical families. Intercontinental matches of shared types among eight continents and subcontinents (Africa, North America, Central America, South America, Europe, the Middle East and Central Asia, and the Far East) are analyzed and discussed.