Laboratory Approach to the Diagnosis of Culture-Negative Infective Endocarditis.

Blood-culture negative endocarditis (BCNE) accounts for up to 35% of all cases of infective endocarditis (IE) and is a serious life-threatening condition with considerable morbidity and mortality. Rapid detection and identification of the causative pathogen is essential for timely, directed therapy. Blood-culture negative endocarditis presents a diagnostic and therapeutic challenge. Causes of BCNE are varied including: treatment with antibiotic agents prior to blood culture collection; sub-optimal specimen collection; and/or infection due to fastidious (eg. nutritionally variant streptococci), intracellular (eg. Coxiella burnetii, Bartonella species) or non-culturable or difficult to culture organisms (eg. Mycobacteria, Tropheryma whipplei and fungi); as well as non-infective aetiologies. Here, we review aetiological and diagnostic approaches to BCNE including newer molecular based techniques, with a brief summary of imaging investigation and treatment principles.