On Calculation of Failure Probability for Structures Designed Based on Magnitudes of Historical Event

During their operational life, structures may be subject to various types of live load caused by events such as earthquakes, high speed winds, etc. Given the design life of a structure, the probability for a specific live load to cause a failure depends on the magnitude of the load structure it is designed to withstand (designed load). In this article, methods are developed for calculation of the failure probability for structures designed to withstand loads comparable to historical loads at the site of interest

Survival Analysis of the Men’s 100 Meter Dash Record

In the 2012 Summer Olympics in London seven out of eight finalists in the men’s 100 meter dash crossed the finish line in under 10 seconds. This result and other recent performances of exceptional sprinters such as Bolt have made experts wonder, not whether a new record will be set, but when and how much it will lower the present record. Seeking an answer, some researchers have tried to model the available data with the goal of using them to predict future records. This article presents a different approach based on theory of records for independent and identically distributed observations. It modifies the number of attempts to break a record to make the results of the theory of records applicable to this situation. The modification is necessary because many sports records have been broken more frequently than what this theory predicts. Two modifications of the number of attempts are considered, fixed rate via a geometric increase, and random rate via a non-homogeneous Poisson process

Natural history of colonization with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE): a systematic review

Background: No published systematic reviews have assessed the natural history of colonization with methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant Enterococcus (VRE). Time to clearance of colonization has important implications for patient care and infection control policy. Methods: We performed parallel searches in OVID Medline for studies that reported the time to documented clearance of MRSA and VRE colonization in the absence of treatment, published between January 1990 and July 2012. Results: For MRSA, we screened 982 articles, identified 16 eligible studies (13 observational studies and 3 randomized controlled trials), for a total of 1,804 non-duplicated subjects. For VRE, we screened 284 articles, identified 13 eligible studies (12 observational studies and 1 randomized controlled trial), for a total of 1,936 non-duplicated subjects. Studies reported varying definitions of clearance of colonization; no study reported time of initial colonization. Studies varied in the frequency of sampling, assays used for sampling, and follow-up period. The median duration of total follow-up was 38 weeks for MRSA and 25 weeks for VRE. Based on pooled analyses, the model-estimated median time to clearance was 88 weeks after documented colonization for MRSA-colonized patients and 26 weeks for VRE-colonized patients. In a secondary analysis, clearance rates for MRSA and VRE were compared by restricting the duration of follow-up for the MRSA studies to the maximum observed time point for VRE studies (43 weeks). With this restriction, the model-fitted median time to documented clearance for MRSA would occur at 41 weeks after documented colonization, demonstrating the sensitivity of the pooled estimate to length of study follow-up. Conclusions: Few available studies report the natural history of MRSA and VRE colonization. Lack of a consistent definition of clearance, uncertainty regarding the time of initial colonization, variation in frequency of sampling for persistent colonization, assays employed and variation in duration of follow-up are limitations of the existing published literature. The heterogeneity of study characteristics limits interpretation of pooled estimates of time to clearance, however, studies included in this review suggest an increase in documented clearance over time, a result which is sensitive to duration of follow-up

Routine HIV Testing in Adolescents and Young Adults Presenting to an Outpatient Clinic in Durban, South Africa

Objectives: Although youth (12–24 years) in Sub-Saharan Africa have a high HIV risk, many have poor access to HIV testing services and are unaware of their status. Our objective was to evaluate the proportion of adolescents (12–17 years) and young adults (18–24 years) who underwent HIV testing and the prevalence among those tested in an urban adult outpatient clinic with a routine HIV testing program in Durban, South Africa. Design: We conducted a retrospective cross-sectional analysis of adolescent and young adult outpatient records between February 2008 and December 2009. Methods: We determined the number of unique outpatient visitors, HIV tests, and positive rapid tests among those tested. Results: During the study period, 956 adolescents registered in the outpatient clinic, of which 527 (55%) were female. Among adolescents, 260/527 (49%, 95% CI 45–54%) females underwent HIV testing compared to 129/429 (30%, 95% CI 26–35%) males (p<0.01). The HIV prevalence among the 389 (41%, 95% CI 38–44%) adolescents who underwent testing was 16% (95% CI 13–20%) and did not vary by gender (p = 0.99). During this period, there were 2,351 young adult registrations, and of these 1,492 (63%) were female. The proportion consenting for HIV testing was similar among females 980/1,492 (66%, 95% CI 63–68%) and males 543/859 (63%, 95% CI 60–66%, p = 0.25). Among the 1,523 (65%, 95% CI 63–67%) young adults who underwent testing, the HIV prevalence was 22% (95% CI 19–24%) in females versus 14% in males (95% CI 11–17%, p<0.01). Conclusions: Although the HIV prevalence is high among youth participating in an adult outpatient clinic routine HIV program, the uptake of testing is low, especially among 12–17 year old males. There is an urgent need to offer targeted, age-appropriate routine HIV testing to youth presenting to outpatient clinics in epidemic settings

Linkage to HIV, TB and Non-Communicable Disease Care from a Mobile Testing Unit in Cape Town, South Africa

Background: HIV counseling and testing may serve as an entry point for non-communicable disease screening. Objectives: To determine the yield of newly-diagnosed HIV, tuberculosis (TB) symptoms, diabetes and hypertension, and to assess CD4 count testing, linkage to care as well as correlates of linkage and barriers to care from a mobile testing unit. Methods: A mobile unit provided screening for HIV, TB symptoms, diabetes and hypertension in Cape Town, South Africa between March 2010 and September 2011. The yield of newly-diagnosed cases of these conditions was measured and clients were followed-up between January and November 2011 to assess linkage. Linkage to care was defined as accessing care within one, three or six months post-HIV diagnosis (dependent on CD4 count) and one month post-diagnosis for other conditions. Clinical and socio-demographic correlates of linkage to care were evaluated using Poisson regression and barriers to care were determined. Results: Of 9,806 clients screened, the yield of new diagnoses was: HIV (5.5%), TB suspects (10.1%), diabetes (0.8%) and hypertension (58.1%). Linkage to care for HIV-infected clients, TB suspects, diabetics and hypertensives was: 51.3%, 56.7%, 74.1% and 50.0%. Only disclosure of HIV-positive status to family members or partners (RR=2.6, 95% CI: 1.04-6.3, p=0.04) was independently associated with linkage to HIV care. The main barrier to care reported by all groups was lack of time to access a clinic. Conclusion: Screening for HIV, TB symptoms and hypertension at mobile units in South Africa has a high yield but inadequate linkage. After-hours and weekend clinics may overcome a major barrier to accessing care

A Paper-Based Multiplexed Transaminase Test for Low-Cost, Point-of-Care Liver Function Testing

In developed nations, monitoring for drug-induced liver injury through serial measurements of serum transaminases [aspartate aminotransferase (AST) and alanine aminotransferase (ALT)] in at-risk individuals is the standard of care. Despite the need, monitoring for drug-related hepatotoxicity in resource-limited settings is often limited by expense and logistics, even for patients at highest risk. This article describes the development and clinical testing of a paper-based, multiplexed microfluidic assay designed for rapid, semiquantitative measurement of AST and ALT in a fingerstick specimen. Using 223 clinical specimens obtained by venipuncture and 10 fingerstick specimens from healthy volunteers, we have shown that our assay can, in 15 min, provide visual measurements of AST and ALT in whole blood or serum, which allow the user to place those values into one of three readout “bins” [5× ULN, corresponding to tuberculosis/HIV treatment guidelines] with >90% accuracy. These data suggest that the ultimate point-of-care fingerstick device will have high impact on patient care in low-resource settings.Chemistry and Chemical Biolog

Routine HIV Screening in Portugal: Clinical Impact and Cost-Effectiveness

Objective: To compare the clinical outcomes and cost-effectiveness of routine HIV screening in Portugal to the current practice of targeted and on-demand screening. Design: We used Portuguese national clinical and economic data to conduct a model-based assessment. Methods: We compared current HIV detection practices to strategies of increasingly frequent routine HIV screening in Portuguese adults aged 18-69. We considered several subpopulations and geographic regions with varying levels of undetected HIV prevalence and incidence. Baseline inputs for the national case included undiagnosed HIV prevalence 0.16%, annual incidence 0.03%, mean population age 43 years, mean CD4 count at care initiation 292 cells/μL, 63% HIV test acceptance, 78% linkage to care, and HIV rapid test cost €6 under the proposed routine screening program. Outcomes included quality-adjusted survival, secondary HIV transmission, cost, and incremental cost-effectiveness. Results: One-time national HIV screening increased HIV-infected survival from 164.09 quality-adjusted life months (QALMs) to 166.83 QALMs compared to current practice and had an incremental cost-effectiveness ratio (ICER) of €28,000 per quality-adjusted life year (QALY). Screening more frequently in higher-risk groups was cost-effective: for example screening annually in men who have sex with men or screening every three years in regions with higher incidence and prevalence produced ICERs of €21,000/QALY and €34,000/QALY, respectively. Conclusions: One-time HIV screening in the Portuguese national population will increase survival and is cost-effective by international standards. More frequent screening in higher-risk regions and subpopulations is also justified. Given Portugal’s challenging economic priorities, we recommend prioritizing screening in higher-risk populations and geographic settings

Validation and Calibration of a Computer Simulation Model of Pediatric HIV Infection

Background: Computer simulation models can project long-term patient outcomes and inform health policy. We internally validated and then calibrated a model of HIV disease in children before initiation of antiretroviral therapy to provide a framework against which to compare the impact of pediatric HIV treatment strategies. Methods: We developed a patient-level (Monte Carlo) model of HIV progression among untreated children 1,300 untreated, HIV-infected African children. Results: In internal validation analyses, model-generated survival curves fit IeDEA data well; modeled and observed survival at 16 months of age were 91.2% and 91.1%, respectively. RMSE varied widely with variations in CD4% parameters; the best fitting parameter set (RMSE = 0.00423) resulted when CD4% was 45% at birth and declined by 6%/month (ages 0-3 months) and 0.3%/month (ages >3 months). In calibration analyses, increases in IeDEA-derived mortality risks were necessary to fit UNAIDS survival data. Conclusions: The CEPAC-Pediatric model performed well in internal validation analyses. Increases in modeled mortality risks required to match UNAIDS data highlight the importance of pre-enrollment mortality in many pediatric cohort studies

Not All Are Lost: Interrupted Laboratory Monitoring, Early Death, and Loss to Follow-Up (LTFU) in a Large South African Treatment Program

Background: Many HIV treatment programs in resource-limited settings are plagued by high rates of loss to follow-up (LTFU). Most studies have not distinguished between those who briefly interrupt, but return to care, and those more chronically lost to follow-up. Methods: We conducted a retrospective cohort study of 11,397 adults initiating antiretroviral therapy (ART) in 71 Southern African Catholic Bishops Conference/Catholic Relief Services HIV treatment clinics between January 2004 and December 2008. We distinguished among patients with early death, within the first 7 months on ART; patients with interruptions in laboratory monitoring (ILM), defined as missing visits in the first 7 months on ART, but returning to care by 12 months; and those LTFU, defined as missing all follow-up visits in the first 12 months on ART. We used multilevel logistic regression models to determine patient and clinic-level characteristics associated with these outcomes. Results: In the first year on ART, 60% of patients remained in care, 30% missed laboratory visits, and 10% suffered early death. Of the 3,194 patients who missed laboratory visits, 40% had ILM, resuming care by 12 months. After 12 months on ART, patients with ILM had a 30% increase in detectable viremia compared to those who remained in care. Risk of LTFU decreased with increasing enrollment year, and was lowest for patients who enrolled in 2008 compared to 2004 [OR 0.49, 95%CI 0.39–0.62]. Conclusions: In a large community-based cohort in South Africa, nearly 30% of patients miss follow-up visits for CD4 monitoring in the first year after starting ART. Of those, 40% have ILM but return to clinic with worse virologic outcomes than those who remain in care. The risk of chronic LTFU decreased with enrollment year. As ART availability increases, interruptions in care may become more common, and should be accounted for in addressing program LTFU

Cost-Effectiveness of HIV Treatment as Prevention in Serodiscordant Couples

The cost-effectiveness of early antiretroviral therapy (ART) in persons infected with human immunodeficiency virus (HIV) in serodiscordant couples is not known. Using a computer simulation of the progression of HIV infection and data from the HIV Prevention Trials Network 052 study, we projected the cost-effectiveness of early ART for such persons