Suchergebnisse

The potential of location-shift models to find adequate models between the proportional odds model and the non-proportional odds model is investigated. It is demonstrated that these models are very useful in ordinal modelling. While proportional odds models are often too simple, non-proportional odds models are typically unnecessary complicated and seem widely dispensable. In addition, the class of location-shift models is extended to allow for smooth effects. The additive location-shift model contains two functions for each explanatory variable, one for the location and one for dispersion. It is much sparser than hard-to-handle additive models with category-specific covariate functions but more flexible than common vector generalised additive models. An R package is provided that is able to fit parametric and additive location-shift models.

In binary and ordinal regression one can distinguish between a location component and a scaling component. While the former determines the location within the range of the response categories, the scaling indicates variance heterogeneity. In particular since it has been demonstrated that misleading effects can occur if one ignores the presence of a scaling component, it is important to account for potential scaling effects in the regression model, which is not possible in available recursive partitioning methods. The proposed recursive partitioning method yields two trees: one for the location and one for the scaling. They show in a simple interpretable way how variables interact to determine the binary or ordinal response. The developed algorithm controls for the global significance level and automatically selects the variables that have an impact on the response. The modeling approach is illustrated by several real-world applications.

Zusammenfassung
Hintergrund und Ziel der Arbeit
Für die klinische Sichtung in der Zentralen Notaufnahme (ZNA) existiert bisher für den Massenanfall von Verletzten kein standardisierter Sichtungsalgorithmus. Mit dem Erscheinen der vierten überarbeiteten und erweiterten Auflage des Manchester-Triage-Systems (MTS) wird dem Nutzer ein spezielles Präsentationsdiagramm ("Massenanfall") angeboten. In der vorliegenden Studie wurde erstmalig das Präsentationsdiagramm "Massenanfall" des MTS im klinischen Setting hinsichtlich seiner Güte untersucht.

Methodik
In der vorliegenden monozentrischen, prospektiven Studie wurden 215 traumatologische und 235 nichttraumatologische Patienten unter Verwendung des Präsentationsdiagramms "Massenanfall" gesichtet und in eine der drei Sichtungskategorien (SK I–III) eingruppiert.

Ergebnisse
Das MTS-Diagramm stufte die traumatologische Kohorte in 80 % der Fälle korrekt ein. In 15,35 % erfolgte eine Über- und in 4,65 % eine Untertriage. Hierbei wurde eine Sensitivität/Spezifität von 84/99 % für die SK I, 87/78 % für SK II sowie 76/94 % für SK III erreicht. Die nichttraumatologischen Patienten wurden in 59,57 % korrekt kategorisiert sowie in 15,75 % über- und in 24,68 % untertriagiert. Die Sensitivität/Spezifität für SK I lag bei 50/95 %, für SK II bei 49/71 % und für SK III bei 73/65 %.

Diskussion
Zusammenfassend war der Algorithmus leicht und schnell anzuwenden und identifizierte traumatologische Patienten mit lebensbedrohlichen Verletzungen treffsicher. Es wurde aber auch deutlich, dass die Diskriminante "Gehfähigkeit" zu Beginn der Sichtung bzw. rein physiologische Entscheidungskriterien mit einer schlechten Testgüte einhergingen. Nichttraumatologische Krankheitsbilder wurden qualitativ ungenügend kategorisiert.

Background Recruiting asymptomatic participants with early disease stages into studies is challenging and only little is known about facilitators and barriers to screening and recruitment of study participants. Thus we assessed factors associated with screening rates in the MACUSTAR study, a multi-centre, low-interventional cohort study of early stages of age-related macular degeneration (AMD). Methods Screening rates per clinical site and per week were compiled and applicable recruitment factors were assigned to respective time periods. A generalized linear mixed-effects model including the most relevant recruitment factors identified via in-depth interviews with study personnel was fitted to the screening data. Only participants with intermediate AMD were considered. Results A total of 766 individual screenings within 87 weeks were available for analysis. The mean screening rate was 0.6 ± 0.9 screenings per week among all sites. The participation at investigator teleconferences (relative risk increase 1.466, 95% CI [1.018–2.112]), public holidays (relative risk decrease 0.466, 95% CI [0.367–0.591]) and reaching 80% of the site's recruitment target (relative risk decrease 0.699, 95% CI [0.367–0.591]) were associated with the number of screenings at an individual site level. Conclusions Careful planning of screening activities is necessary when recruiting early disease stages in multi-centre observational or low-interventional studies. Conducting teleconferences with local investigators can increase screening rates. When planning recruitment, seasonal and saturation effects at clinical site level need to be taken into account. ; Name of action: Intermediate AMD: Development of novel clinical endpoints for clinical trials in patients with a regulatory and patient access intention - MACUSTAR This project has received funding from the Innovative Medicines Initiative 2 Joint Undertaking under grant agreement No 116076. This Joint Undertaking receives support from the European Union's Horizon 2020 research and ...