Sepsis-related peripheral blood smear findings

The diagnosis of sepsis can be complex due to a broad differential diagnosis which requires a combination of clinical evaluation, vital signs assessment and laboratory workup, represented by a comprehensive metabolic panel, including blood lactate, as well as complete blood count (CBC) with differential. Currently, many serum (plasma) markers are used to effectively screen patients for sepsis. Amongst them, we mention C-reactive protein (CRP), procalcitonin (PCT), presepsin, interleukin 6 (IL-6), and neutrophil CD64 levels⁽¹⁾.

The CBC and leukocyte morphology play a quintessential role in the early diagnosis of sepsis. Peripheral blood smears can display various anomalies of granulocytes, monocytes and erythrocytes. Neutrophils can exhibit rod-shaped nuclei, toxic granulation, cytoplasmic vacuoles and Dohle bodies. We also note the presence of bandemia (band neutrophils above 10% of the total white blood cell count), considering the significantly higher incidence of bacteremia reported in cases displaying bandemia⁽²⁾. Other indicators that involve granulocytes are polymorphonuclear neutrophils with a diameter greater than 14 µm, referred to as macropolycytes. They missed a cell division and, therefore, they are tetraploid⁽³⁾. The cytoplasmic particles of lymphocytes are increased, and so is their volume. Monocytes migrate and undergo deformation, their volume and morphology changing to some extent⁽⁴⁾. Crouser et al. established that the morphological variability that takes place during monocyte activation in the early inflammatory response can be assessed by measuring the monocyte distribution width (MDW), an indicator of monocyte anisocytosis. A study showed that MDW could be a novel cellular marker that may help detect sepsis early⁽⁵⁾.

Alterations of erythrocyte membrane and cytoskeleton can occur in early sepsis, that result in disintegrating erythrocytes, and/or erythrocyte aggregates (or clumps). Recent studies have revealed the generation of both stomatocytes and echinocytes in septic patients⁽⁶⁾.

We present the following images of peripheral blood smear related to four clinical cases:

• The case of a male patient with positive blood cultures for Escherichia coli, exhibiting large hypergranulated neutrophils with cytoplasmic vacuoles (Figure A).
• The cases of two oncologic patients (Figure B – pancreatic cancer; Figure C – prostate cancer), with hepatitis C virus reactivation during follow-up, exhibiting polymorphic monocytes, with various nuclear shapes and intense cytoplasmic vacuolation.
• The case of a female patient with Campylobacter spp. detected in peritoneal fluid, displaying neutrophils with blue cytoplasmic inclusions – Döhle bodies (Figure D).
• The case of a male patient with sepsis caused by methicillin-resistant Staphylococcus aureus, presenting RBC 3.59 x 10⁶/µL, Hb 13 g/dL, MCV 104.2 fL, MCH 36.2 pg, and small erythrocyte aggregates on peripheral blood smear (Figure E).

The pictures were available with CellaVision Periphe­ral Blood Application software, MGG, 100x magnification.

Efforts have been made to reduce the burden of sepsis. Predicting the risk of sepsis development could reduce mortality by avoiding multiorgan dysfunction proces­ses. To date, the ideal biomarker of sepsis has not been identified, due to disease heterogeneity. Integrated evaluation based on laboratory and clinical findings can help clinicians recognize it early. CBC parameters have great potential. Considerably, morphologic abnormalities visualized on peripheral blood smear could represent a warning sign for clinicians, prompting for further investigation. Additionally, diversity in morphological development could assist clinicians in defining the severity of sepsis and in monitoring the therapy⁽⁷⁾.   

Corresponding author: Cătălina Grosu-Ferea E-mail: catalina-roxana.ferea@rez.umfcd.ro

Conflict of interest: none declared.

Financial support: none declared.

This work is permanently accessible online free of charge and published under the CC-BY licence.