How frequent are meta-analyses with “double-zero” studies in systematic reviews?

Oliver Kuß, Michaela Wandrey & Mareike Kunze
Introduction: Meta-analyses for rare binary (e.g., adverse events or safety) outcomes often include studies that have no events in one (“single-zero”) or even both (“double-zero”) treatment arms. A variety of methods to deal with this problem statistically have been proposed.[for full text, please go to the a.m. URL]