Marik PE, et al. - Researchers undertook this retrospective, observational, Electronic Medical Record based study to assess four easily available biomarkers—procalcitonin (PCT), serum lactate level, total white blood cell (WBC) count and the neutrophil-lymphocyte count ratio (NLCR)—for their diagnostic accuracy to diagnose blood stream infection (BSI) among patients with suspected sepsis. Overall 1,767 discreet patient admissions were analyzed. The findings are suggestive of the likely effectiveness of PCT of less than 0.5 ng/mL as a screening instrument to exclude BSI as the reason for sepsis, while consideration should be given to BSI diagnosis in patients with a PCT above this threshold. For BSI diagnosis, total WBC count and blood lactate level may not be reliable biomarkers. Experts suggested the likely usefulness of NLCR as a screening test for BSI when PCT assays are not available.