The review question was clear. Inclusion criteria were broad for study design but potentially replicable for all aspects. Several relevant data sources were searched. The restriction to papers in English meant that some studies may have been overlooked. There was no reported study quality assessment and it was unclear whether attempts were made to minimise error and bias in the review process. These shortcomings were potential threats to the reliability of the review findings.
The authors overall conclusion suggested that a statistical synthesis was carried out but a pooled effect was not reported. There was no assessment of statistical heterogeneity and substantial clinical variation was evident from the study tables.
The authors' conclusion reflects the evidence in terms of a trend between increased nurse staffing and decreased adverse patient outcomes. Given the uncertain quality of the included studies and the inability to judge the robustness of the review process, the reliability of these statements is uncertain.