Outbreak column 19: needleless connectors (NCs) tales from nine outbreaks.

A critical review of historical outbreak reports that are still influencing practice today is presented.  These outbreak reports were used as evidence in support of guideline recommendations and of the US Food and Drug Administration's (FDA) advisory notice requiring post-product surveillance for needleless connectors (NC) which have a positive displacement. Guideline recommendations were subsequently changed but not before other authorities had issued recommendations based on the original.  All the above led some purchasers to look for different NC designs.  The conclusions are that the evidence, as reported, does not support there being an increased risk from positive displacement NCs. Identified in this review were unsubstantiated claims, incompleteness in reporting of specifics, opinions considered as evidence and unexplored outbreak-provoking explanations.