Ratings Use in an Online Discussion System: The Slashdot Case

Large-scale, online communication systems allow many-to-many interactions among users, which can result in a variety of positive outcomes. However, the prevalence of information overload and problems caused by the loss of shared communication channels in text-based environments may create barriers to realizing the benefits of online interactions. Attempts to manage online communication systems in the past depended on techniques that cannot be applied to, or do not allow, large-scale interactions. Slashdot is a large-scale, long-lasting Web discussion community that uses a form of recommendation system to provide feedback about the quality of comments users post to the site. This dissertation examines this novel approach to organizing an online communication system in terms of how users employ the ratings provided by the system, whether comment ratings have an effect on how new users of the site participate, and how users making recommendations about content actually provide ratings. I find that users do employ ratings to change how they view content, but that there is some resistance that prevents them from doing so readily. To overcome this friction, I recommend dynamic changes based on the choices of other users who seem more willing to make interface changes based on comment ratings. I also find that new user participation on Slashdot is affected by feedback on the initial comment made by the new member, but that user observation is just as important in determining how the new member will participate in the future. Finally, I find that ratings are being sufficiently applied to comments, but that some comments are not receiving fair attention because of when or where they are posted within the online discussion. The overall conclusions of this work are that pre-rating content helps to relieve the pressure of attaining sufficient ratings on comments, that rating labels provide valuable feedback for customizing how users with different motivations may read comments, and that comments ratings positively affect user experiences in a large, online discussion system. The Slashdot case shows how the use of recommendations in an online discussion system creates organization that ameliorates the problems of information overload and loss of communication channels, while still allowing for large-scale, heterogeneous interactions.Ph.D.InformationUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/39369/2/lampe_diss_revised.pd

Development and Validation of a Risk Score for Chronic Kidney Disease in HIV Infection Using Prospective Cohort Data from the D:A:D Study

Ristola M. on työryhmien DAD Study Grp ; Royal Free Hosp Clin Cohort ; INSIGHT Study Grp ; SMART Study Grp ; ESPRIT Study Grp jäsen.Background Chronic kidney disease (CKD) is a major health issue for HIV-positive individuals, associated with increased morbidity and mortality. Development and implementation of a risk score model for CKD would allow comparison of the risks and benefits of adding potentially nephrotoxic antiretrovirals to a treatment regimen and would identify those at greatest risk of CKD. The aims of this study were to develop a simple, externally validated, and widely applicable long-term risk score model for CKD in HIV-positive individuals that can guide decision making in clinical practice. Methods and Findings A total of 17,954 HIV-positive individuals from the Data Collection on Adverse Events of Anti-HIV Drugs (D:A:D) study with >= 3 estimated glomerular filtration rate (eGFR) values after 1 January 2004 were included. Baseline was defined as the first eGFR > 60 ml/min/1.73 m2 after 1 January 2004; individuals with exposure to tenofovir, atazanavir, atazanavir/ritonavir, lopinavir/ritonavir, other boosted protease inhibitors before baseline were excluded. CKD was defined as confirmed (>3 mo apart) eGFR In the D:A:D study, 641 individuals developed CKD during 103,185 person-years of follow-up (PYFU; incidence 6.2/1,000 PYFU, 95% CI 5.7-6.7; median follow-up 6.1 y, range 0.3-9.1 y). Older age, intravenous drug use, hepatitis C coinfection, lower baseline eGFR, female gender, lower CD4 count nadir, hypertension, diabetes, and cardiovascular disease (CVD) predicted CKD. The adjusted incidence rate ratios of these nine categorical variables were scaled and summed to create the risk score. The median risk score at baseline was -2 (interquartile range -4 to 2). There was a 1: 393 chance of developing CKD in the next 5 y in the low risk group (risk score = 5, 505 events), respectively. Number needed to harm (NNTH) at 5 y when starting unboosted atazanavir or lopinavir/ritonavir among those with a low risk score was 1,702 (95% CI 1,166-3,367); NNTH was 202 (95% CI 159-278) and 21 (95% CI 19-23), respectively, for those with a medium and high risk score. NNTH was 739 (95% CI 506-1462), 88 (95% CI 69-121), and 9 (95% CI 8-10) for those with a low, medium, and high risk score, respectively, starting tenofovir, atazanavir/ritonavir, or another boosted protease inhibitor. The Royal Free Hospital Clinic Cohort included 2,548 individuals, of whom 94 individuals developed CKD (3.7%) during 18,376 PYFU (median follow-up 7.4 y, range 0.3-12.7 y). Of 2,013 individuals included from the SMART/ESPRIT control arms, 32 individuals developed CKD (1.6%) during 8,452 PYFU (median follow-up 4.1 y, range 0.6-8.1 y). External validation showed that the risk score predicted well in these cohorts. Limitations of this study included limited data on race and no information on proteinuria. Conclusions Both traditional and HIV-related risk factors were predictive of CKD. These factors were used to develop a risk score for CKD in HIV infection, externally validated, that has direct clinical relevance for patients and clinicians to weigh the benefits of certain antiretrovirals against the risk of CKD and to identify those at greatest risk of CKD.Peer reviewe