The last item of the Downs and Black checklist is an assessment of the adequacy of the sample size of the study, which we performed assuming a two-sided P Idelalisib value of 0.05, 80% power, and a 10% relative difference for the main outcome measure.Statistical analysisA meta-analytic approach was planned by using Mantel-Haenztel random-effect models, if deemed appropriate. We presented outcome data by using odds ratios with 95% confidence intervals. An odds ratio of less than 1 suggests a lower rate of the event among the patients exposed to lower hemoglobin levels. Continuous data, such as length of stay and physiologic parameters, were reported as mean or median. We summarized continuous data as mean difference with 95% confidence intervals. We converted hematocrit to hemoglobin by using a standard published equation [25] (Hb [g/dl] = Hct [%]/3).
All data were compiled in Review Manager (version 5.0; The Cochrane Collaboration). A priori sensitivity analyses were planned to explore heterogeneity in study findings, based on age, type of neurocritical condition, risk of bias, and presence of co-interventions.ResultsSearch resultsOur literature search yielded 4,310 studies from major databases after removal of duplicate records (Figure (Figure1).1). Seven studies were deemed potentially elligible [6,26-31], but one was excluded, as it reported only summary data for the overall group [31]. The authors of the latter study were contacted and confirmed that data from each study group were unavailable. Therefore, six studies were included (number of patients = 537) [6,26-30].
The overall interrater agreement between reviewers on inclusion was high (Cohen kappa = 0.80). Discrepancies were resolved with the input of a third reviewer on two occasions.Figure 1Flow diagram of study selection. Hb, hemoglobin concentration; NCP, neurocritically ill patient.Data for the subgroup of neurocritically ill patients from a previous RCT on transfusion thresholds in pediatric ICUs were obtained from the authors for one study [6]. Attempts to contact the authors of two other studies to obtain data on subgroups of published RCTs were unsuccessful [32,33]. Two abstracts of potentially relevant studies were retrieved through the review of conference proceedings; however, one reported data on a study already included in our review [29,34], whereas the other abstract [35] had not yet been published as a full report.
Additional data for this study could not be obtained from the corresponding author. Of note, one relevant ongoing study was identified [36].Study characteristicsAmong the six studies included, three were from the United States [28-30], two from Canada [26,28], and one was completed in Switzerland [27] (Table (Table1).1). All studies were published in peer-reviewed English language journals within Cilengitide the last 5 years, and the period over which the studies were conducted spanned from 1994 to 2011.