Sepsis is an abnormal host response to infection that leads to a dysfunction of one or several organs. The Third International Sepsis Consensus has recently revised the definition of sepsis and septic shock, and has proposed the use of the sequential organ failure assessment (SOFA) score to evaluate acute organ dysfunction.1  The use of SOFA is preferred over qSOFA (quick sequential organ failure assessment) or SIRS (systemic inflammatory response syndrome) criteria in intensive care unit (ICU) patients, but outside the ICU, qSOFA can be easily used in clinical practice as its validity appears to be higher than that of SOFA and SIRS.2 The search for sepsis biomarkers continues as there are ongoing trials for the identification and validation of tests useful in diagnosis, monitoring, or prognosis assessment. From procalcitonin to presepsin to soluble urokinase-type plasminogen activator receptor (suPAR), each proposed biomarker has its advantages and disadvantages, and most of the novel biomarkers are limited to initial use in selected clinical facilities with specialized laboratories, prior to entering clinical practice worldwide. Therefore, a return to the basics is much needed, and recent studies have shown that simple, readily available tests such as the mean platelet volume (MPV) or the platelet distribution width (PDW) can be considered useful sepsis biomarkers under certain circumstances. For example, a study from 2014 involving preterm infants has shown that sepsis was associated with low platelet counts and high MPV and PDW values. Importantly, the higher the MPV the higher the mortality in this specific cohort, with 10.35 fL proposed as cut-off for sepsis diagnosis and 10.75 fL proposed as cut-off for prognosis of mortality.3 These results are also in accordance with an older study that included very low birth weight neonates, and that also showed that different pathogens cause different host responses in terms of platelet dynamics, namely that Gram-negative or fungal sepsis associate lower platelet counts compared to Gram-positive sepsis.4 A different study confirmed that mortality is increased among neonates with thrombocytopenia, but failed to obtain a statistically significant correlation between MPV, PDW and mortality.5  Adult patients with sepsis have shown similar kinetics of platelet counts and MPV, with fungal sepsis being associated with more profound and prolonged thrombocytopenia as well as higher values of MPV, followed by Gram-negative sepsis, while Gram-positive sepsis associated the least pronounced changes in platelet dynamics.6 In conclusion, MPV, PDW and thrombocytopenia are readily available tests that are routinely performed and can be used in selected cases of sepsis to assess prognosis, risk of mortality and to monitor the progression of the disease.

1. Singer M, Deutschman CS, Seymour CW, et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA 2016;315:801-10. [Crossref]

2. Seymour CW, Liu VX, Iwashyna TJ, et al. Assessment of Clinical Criteria for Sepsis: For the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA 2016;315:762-74. [Crossref]

3. Catal F, Tayman C, Tonbul A, et al. Mean platelet volume (MPV) may simply predict the severity of sepsis in preterm infants. Clin Lab 2014;60:1193-200.

4. Guida JD, Kunig AM, Leef KH, McKenzie SE, Paul DA. Platelet count and sepsis in very low birth weight neonates: is there an organism-specific response? Pediatrics 2003;111:1411-5. [Crossref]

5. Ahmad MS, Waheed A. Platelet counts, MPV and PDW in culture proven and probable neonatal sepsis and association of platelet counts with mortality rate. J Coll Physicians Surg Pak 2014;24:340-4. [Crossref]

6. Aydemir H, Piskin N, Akduman D, Kokturk F, Aktas E. Platelet and mean platelet volume kinetics in adult patients with sepsis. Platelets 2015;26:331-5. [Crossref]