Klaske van Sluis

Objective and subjective voice outcomes: a systematic review 23 groups within one study. Speaker groups had to be gr n =7. There had to be a comparison of two or more speaker groups within the study. At least one of the primary outcome measurements had to be reported. Studies were graded ac- cording to the criteria of risk on bias described by the Cochrane Handbook for Systematic Reviews of Interventions, shown in the appendix, i.e. A = low risk of bias, B = unclear risk of bias, and C = high risk of bias [25, 26]. Level A and level B rated studies were included. Articles were excluded when they mainly reported on device research, primary or secondary voice prosthesis placement, adverse effects, or on pulmonary rehabilitation. Articles only reporting on sec- ondary outcomes or rated as a Level C article were excluded. Reference lists were checked to collect more data. Studies which were rated with low risk of bias (level A) were indicated as best evidence available. These level A rated studies are highlighted in the result section, as well as the significant outcomes reported by the included studies (level A and B). Only predefined outcome pa- rameters were taken into account. Outliers were excluded in the overall results section and are elaborated on further in the discussion section. Outcomes of in- cluded studies were analyzed and, where possible, pooled. Data were tabulated and graphically represented in violin plots. 2.3 Results The search and selection process is visualized in Figure 1. The first and second author screened 50 out of 2405 papers on title and abstract to meet the selection criteria for inclusion. The first author performed the remaining screening of titles and abstracts. Seventy papers were evaluated in full for relevance and validity by the first and second author. References of the articles that were retrieved in full were screened, which resulted in two additional articles. The first and second author both performed a critical appraisal of the design of the studies. The third author evaluated all non-English articles. A decision on the inclusion of the articles was made in consensus of the three raters. The definitive selection included 28 publications. There were two papers that discussed the same study, but were written in two different languages [27, 28]. We included the English version [27]. Furthermore, there were two publications of the same author published in 2013 and 2015, the 2015 pa- per containing additional speakers and evaluations to the 2013 paper [29, 30]. Therefore, we have chosen to only report on the 2015 paper in this systematic review [30]. This left 26 papers for further evaluation (Table 2.2). In Table 2.2 details of the selected studies are provided. The scope of the research, the number of included participants and risk of bias rating is shown. In total, only three of the 26 studies (12%) reached level A (low risk of bias), shown in bold [30–32]. The remaining articles reached level B (unclear risk of bias). A total of 1,097 participants are included in the studies, only the groups of interest are taken into account. Groups of interest were ES ( n =313), TES