Relationship between volume and outcome for congenital diaphragmatic hernia: a systematic review protocol

Congenital diaphragmatic hernia is a rare and life-threatening anomaly that occurs during fetal development and results in an incomplete or incorrect formation of the diaphragm. Surgical therapy of the diaphragm should be performed after clinical stabilization of the neonate. Higher hospital or surgeon volume has previously been found to be associated with better clinical outcomes for different especially high-risk, low-volume procedures. Therefore, we aim to examine the relationship between hospital or surgeon volume and outcomes for congenital diaphragmatic hernia.

This systematic review protocol has been designed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocol. We will perform a systematic literature search in MEDLINE, Embase, CINAHL and Biosis Previews without applying any limitations. In addition, we will search for relevant conference abstracts. We will screen titles and abstracts of retrieved studies, obtain potentially relevant full texts, and assess the eligibility of those full texts against our inclusion criteria. We will include comparative studies analyzing the relationship between hospital or surgeon volume and clinical outcomes. We will systematically assess risk of bias of included studies and extract data on the study design, patient characteristics, case-mix adjustments, statistical methods, hospital and surgeon volume, and outcomes into standardized tables. Title and abstract screening, full-text screening, critical appraisal, and data extraction of results will be conducted by two reviewers independently. Other data will be extracted by one reviewer and checked for accuracy by a second one. Any disagreements will be resolved by discussion. We will not perform a meta-analysis as we expect included studies to be clinically and methodologically very diverse. We will synthesize findings from primary studies in a structured narrative way and using GRADE.

Given the lack of a comprehensive summary of findings on the relationship between hospital or surgeon volume and outcomes for congenital diaphragmatic hernia, this systematic review will put things right. Results can be used to inform decision makers or clinicians and to adapt medical care.

PROSPERO (CRD42018090231)