High immature platelet fraction with reduced platelet count on hospital admission. Can it be useful for COVID-19 diagnosis?

Immature platelets in COVID-19

Platelets play a critical role in immune response. Coronavirus disease 2019 (COVID-19) patients with a severe course often show pathological coagulation parameters including thrombocytopenia, and at the same time the proportion of immature platelets increases. In this study, the platelet count and the immature platelet fraction (IPF) of hospitalized patients with different oxygenation requirements was investigated daily over a course of 40 days. In addition, the platelet function of COVID-19 patients was analyzed. It was found that the number of platelets in patients with the most severe course (intubation and extracorporeal membrane oxygenation (ECMO)) was significantly lower (111.5 ∙ 10⁶ /mL) than in the other groups (mild (no intubation, no ECMO): 203.5 ∙ 10⁶ /mL, p < .0001, moderate (intubation, no ECMO): 208.0 ∙ 10⁶ /mL, p < .0001). IPF tended to be elevated (10.9%). Platelet function was reduced. Differentiation by outcome revealed that the deceased patients had a highly significant lower platelet count and higher IPF (97.3 ∙ 10⁶ /mL, p < .0001, 12.2%, p = .0003).

Leukocyte cell population data as potential markers of COVID-19 disease characterization

Background

The usefulness of leukocyte cell population data (CPD) is currently being investigated. In COVID-19 pandemic several reports showed the clinical importance of hematological parameters. Our study aimed to assess CPDs in Sars CoV-2 patients as new disease markers.

Methods

From February to April 2020 (1st wave) 540 and from September to December 2020 (2nd wave) 2821 patients respectively were enrolled. SARS CoV-2 infection diagnosis was carried out by Multiplex rRT-PCR from nasopharyngeal swabs. CPDs were detected by XN 2000 hematology analyzer (Sysmex Corporation). A comparison between two disease waves was performed. Additionally, C-reactive protein (CRP) and lactate dehydrogenase (LDH) were assayed.

Results

CPDs were classified into: cell complextity, DNA/RNA content and abnormal sized cells. We detected parameters increased from the reference population for all cell types for both 1st and 2nd wave (p<0.05). However, in the 2nd vs 1st wave 5 CPDs vs 9 CPDs were found. In addition we observed higher CPD values of the 1st compared to 2nd wave: (NE-SFL) (p<0.001), (LY-Y) (p<0.0001), (LY-Z) (p<0.0001), (MO-X) (p<0.0001), (MO-Y) (p<0.0001). These findings were confirmed by the higher concentrations of CRP and LDH in the 1st vs 2nd wave: 17.3 mg/L (8.5-59.3) vs 6.3 mg/L (2.3-17.6) (p<0.001) and 241.5 IU/L (201-345) vs 195 IU/L (174-228) (p< 0.001) (median, interquartile range) respectively.

Conclusions

CPDs showed increased cell activation in 1st wave patients confirmed by clinical and biochemical data, associated with worse clinical conditions. Results highlighted the CPDs as disease characterization markers or useful for a risk model.

A Novel Predictive Model in Recognizing Severe COVID-19 and Multiorgan Injuries: Platelet-to-CRP Ratio

Aims

In view of the emerging virus variations and pandemic worldwide, it is urgent to explore effective models predicting disease severity.

Methods

We aimed to investigate whether platelet-to-CRP ratio (PC ratio) could predict the severity of COVID-19 and multi-organ injuries. Patients who complained of pulmonary or gastrointestinal symptoms were enrolled after confirmation of SARS-CoV-2 infection via qRT-PCR. Those who complained of gastrointestinal symptoms were defined as having initial gastrointestinal involvement. Chest computed tomography (CT) was then performed to classify the patients into mild, moderate, and severe pneumonia groups according to the interim management guideline. qRT-PCR was also performed on stool to discern those discharging virus through the gastrointestinal tract. Logistic regression models were applied to analyze the association between PC ratio and severity of pneumonia, risk of initial gastrointestinal involvement, and multi-organ injuries.

Results

When compared to the bottom tertile of PC ratio, the adjusted odds ratio was −0.51, p < 0.001 and −0.53, p < 0.001 in moderate and severe pneumonia, respectively. Furthermore, the adjusted odds ratio for initial gastrointestinal involvement was 0.18 (82% lower) when compared to the bottom tertile of PC ratio, p=0.005. The area under ROC on moderate-to-severe pneumonia and initial gastrointestinal involvement was 0.836 (95% CI: 0.742, 0.930, p < 0.001) and 0.721 (95% CI: 0.604, 0.839, p=0.002), respectively. The upper tertiles of PC ratio showed lower levels of aspartate aminotransferase (p=0.016) and lactic dehydrogenase (p < 0.001).

Conclusions

Platelet-to-CRP ratio could act as an effective model in recognizing severe COVID-19 and multi-organ injuries.

Reference intervals for Sysmex XN hematological parameters as assessed in the Dutch Lifelines cohort

OBJECTIVES

Our aim was to derive reference intervals for all Sysmex XN hematology analyzer parameters. The rationale behind the study was the lack of reference intervals for the XN analyzer cell population data (CPD) and functional parameters.

METHODS

Fresh fasting blood samples from 18,484 participants in the Dutch Lifelines study were analyzed using two automated XN analyzers. Structured health questionnaire data were used to select a subgroup of 15,803 apparently healthy individuals for inclusion in the reference population. The Latent Abnormal Values Exclusion (LAVE) approach was used to reduce the influence of latent diseases in the reference population on the resulting reference intervals. We applied analysis of variance to judge the need for partitioning of the reference intervals by sex or age.

RESULTS

We report reference intervals for 105 XN analyzer hematological parameters with and without applying LAVE. Sex-related partitioning was required for red blood cells, (RBC, RBC-O), hemoglobin (HGB, HGB-O), hematocrit (HCT), mean corpuscular hemoglobin concentration (MCHC), reticulocyte production index (RPI), and side scattered light intensity of the red blood cell population in the RET channel (RBC-Z). Partitioning for age was not warranted. Body mass index (BMI) and smoking had moderate influence on a minority of the parameters.

CONCLUSIONS

We provide reference intervals for all Sysmex XN analyzer routine, CPD and functional parameters, using a direct approach in a large cohort in the Netherlands.

Platelet Subtypes in Inflammatory Settings

In addition to their essential role in hemostasis and thrombosis, platelets also modulate inflammatory reactions and immune responses. This is achieved by specialized surface receptors as well as secretory products including inflammatory mediators and cytokines. Platelets can support and facilitate the recruitment of leukocytes into inflamed tissue. The various properties of platelet function make it less surprising that circulating platelets are different within one individual. Platelets have different physical properties leading to distinct subtypes of platelets based either on their function (procoagulant, aggregatory, secretory) or their age (reticulated/immature, non-reticulated/mature). To understand the significance of platelet phenotypic variation, qualitatively distinguishable platelet phenotypes should be studied in a variety of physiological and pathological circumstances. The advancement in proteomics instrumentation and tools (such as mass spectrometry-driven approaches) improved the ability to perform studies beyond that of foundational work. Despite the wealth of knowledge around molecular processes in platelets, knowledge gaps in understanding platelet phenotypes in health and disease exist. In this review, we report an overview of the role of platelet subpopulations in inflammation and a selection of tools for investigating the role of platelet subpopulations in inflammation.