Procoagulant phenotype of virus-infected pericytes is associated with portal thrombosis and intrapulmonary vascular dilations in fatal COVID-19.

BACKGROUND & AIMS: Mechanisms and clinical impact of portal microthrombosis featuring severe COVID-19 are unknown. Intrapulmonary vascular dilation (IPVD)-related hypoxia has been described in severe liver diseases. We hypothesized that portal microthrombosis is associated with IPVD and fatal respiratory failure in COVID-19. METHODS: Ninety-three patients who died from COVID-19, were analysed for portal microvascular damage (histology), IPVD (histology and chest-computed tomography, CT), and hypoxemia (arterial blood gas). Seventeen patients who died from COVID-19-unrelated pneumonia served as controls. Vascular lesions and microthrombi were phenotyped for endothelial (vWF) and pericyte (αSMA/PDGFR-ß) markers, tissue factor (TF), viral spike-protein and nucleoprotein (SP, NP), fibrinogen, platelets (CD41a). Viral particles in vascular cells were assessed by transmission electron microscopy (TEM). Cultured pericytes were infected with SARS-CoV-2 to measure TF expression and tubulisation of human pulmonary microvascular endothelial cells (HPMEC) was assessed upon vWF treatment. RESULTS: IPVD was present in 16/66 COVID-19 patients with both liver and lung histology, with a younger age (62 vs 78yo), longer illness (25 vs 14 days), worsening hypoxemia (PaO2/FiO2 from 209 to 89), and more ventilatory support (63 vs 22%) compared to COVID-19/Non-IPVD. IPVD, absent in controls, were confirmed by chest-CT. COVID-19/IPVD liver histology showed portal microthrombosis in >82.5% of portal areas, with a thicker wall of αSMA/PDGFR-ß+/ SP+/NP+ pericytes compared with COVID-19/Non-IPVD. Thrombosed portal venules correlated with αSMA+ area, whereas infected SP+/NP+ pericytes expressed TF. SARS-CoV-2 viral particles were observed in portal pericytes. In-vitro SARS-CoV-2 infection of pericytes up-regulated TF and induced endothelial cells to overexpress vWF, which expanded HPMEC tubules. CONCLUSIONS: SARS-CoV-2 infection of liver pericytes elicits a local procoagulant response associated with extensive portal microthrombosis, IPVD and worsening respiratory failure in fatal COVID-19. IMPACT AND IMPLICATIONS: Vascular involvement of the liver represents a serious complication of COVID-19 infection that must be considered in the work-up of patients with long-lasting and progressively worsening respiratory failure, as it may associate with the development of intrapulmonary vascular dilations. This clinical picture is associated with a pro-coagulant phenotype of portal venule pericytes, which is induced by SARS-CoV-2 infection of pericytes. Both observations provide a model that may apply, at least in part, to other vascular disorders of the liver, featuring obliterative portal venopathy, similarly characterized at the clinical level by development of hypoxemia and at the histological level, by phlebosclerosis and reduced caliber of the portal vein branches in the absence of cirrhosis. Moreover, our findings bring light to an as yet overlooked player of thrombosis pathophysiology, i.e. pericytes, which may provide novel therapeutic tools to halt prothrombotic mechanisms.

Multicentric evaluation of the variability of digital morphology performances also respect to the reference methods by optical microscopy.

INTRODUCTION: Despite the important diagnostic role of peripheral blood morphology, cell classification is subjective. Automated image-processing systems (AIS) provide more accurate and objective morphological evaluation. The aims of this multicenter study were the evaluation of the intra and inter-laboratory variation between different AIS in cell pre-classification and after reclassification, compared with manual optical microscopy, the reference method. METHODS: Six peripheral blood samples were included in this study, for each sample, 70 May-Grunwald and Giemsa stained PB smears were prepared from each specimen and 10 slides were delivered to the seven laboratories involved. Smears were processed by both optical microscopy (OM) and AIS. In addition, the assessment times of both methods were recorded. RESULTS: Within-laboratory Reproducibility ranged between 4.76% and 153.78%; between-laboratory Precision ranged between 2.10% and 82.2%, while Total Imprecision ranged between 5.21% and 20.60%. The relative Bland Altman bias ranged between -0.01% and 20.60%. The mean of assessment times were 326 ± 110 s and 191 ± 68 s for AIS post reclassification and OM, respectively. CONCLUSIONS: AIS can be helpful when the number of cell counted are low and can give advantages in terms of efficiency, objectivity and time saving in the morphological analysis of blood cells. They can also help in the interpretation of some morphological features and can serve as learning and investigation tools.

Performance evaluation of automated cell counts compared with reference methods for body fluid analysis.

OBJECTIVES: Cellular analysis of body fluids (BFs) can assist clinicians for the diagnosis of many medical conditions. The aim of this work is the evaluation of the analytical performance of the UF-5000 body fluid mode (UF-BF) analyzer compared to the gold standard method (optical microscopy, OM) and to XN-1000 (XN-BF), another analyzer produced by the same manufacturer (Sysmex) and with a similar technology for BF analysis. METHODS: One hundred BF samples collected in K3EDTA tubes were analyzed by UF-BF, XN-BF and OM. The agreement was evaluated using Passing and Bablok regression and Bland-Altman plot analysis. The receiver operating characteristic (ROC) curves were selected for evaluating the diagnostic agreement between OM classification and UF-BF parameters. RESULTS: Comparison between UF-BF and OM, in all BF types, showed Passing and Bablok's slope comprised between 0.99 (polymorphonuclear cells count, PMN-BF) and 1.39 (mononuclear cells count, MN-BF), the intercepts ranged between 26.47 (PMN-BF parameter) and 226.80 (white blood cell count). Bland-Altman bias was comprised between 7.3% (total cell count, TC-BF) and 52.9% (MN-BF). Comparison between UF-BF and XN-BF in all BF showed slopes ranged between 1.07 (TC-BF and PMN-BF) and 1.16 (MN-BF), intercepts ranged between 8.30 (PMN) and 64.78 (WBC-BF). Bland-Altman bias ranged between 5.8 (TC-BF) and 21.1% (MN-BF). The ROC curve analysis showed an area under the curve ranged between 0.9664 and 1.000. CONCLUSIONS: UF-BF shows very good performance for the differential counts of cells in ascitic, pleural and synovial fluids and therefore it is useful to screen and count cells in this type of BF.

The importance of being external. methodological insights for the external validation of machine learning models in medicine.

Background and Objective Medical machine learning (ML) models tend to perform better on data from the same cohort than on new data, often due to overfitting, or co-variate shifts. For these reasons, external validation (EV) is a necessary practice in the evaluation of medical ML. However, there is still a gap in the literature on how to interpret EV results and hence assess the robustness of ML models. METHODS: We fill this gap by proposing a meta-validation method, to assess the soundness of EV procedures. In doing so, we complement the usual way to assess EV by considering both dataset cardinality, and the similarity of the EV dataset with respect to the training set. We then investigate how the notions of cardinality and similarity can be used to inform on the reliability of a validation procedure, by integrating them into two summative data visualizations. RESULTS: We illustrate our methodology by applying it to the validation of a state-of-the-art COVID-19 diagnostic model on 8 EV sets, collected across 3 different continents. The model performance was moderately impacted by data similarity (Pearson ρ = 0.38, p< 0.001). In the EV, the validated model reported good AUC (average: 0.84), acceptable calibration (average: 0.17) and utility (average: 0.50). The validation datasets were adequate in terms of dataset cardinality and similarity, thus suggesting the soundness of the results. We also provide a qualitative guideline to evaluate the reliability of validation procedures, and we discuss the importance of proper external validation in light of the obtained results. CONCLUSIONS: In this paper, we propose a novel, lean methodology to: 1) study how the similarity between training and validation sets impacts the generalizability of a ML model; 2) assess the soundness of EV evaluations along three complementary performance dimensions: discrimination, utility and calibration; 3) draw conclusions on the robustness of the model under validation. We applied this methodology to a state-of-the-art model for the diagnosis of COVID-19 from routine blood tests, and showed how to interpret the results in light of the presented framework.

Pathological characteristics of liver sinusoidal thrombosis in COVID-19 patients: A series of 43 cases.

AIM: Coronavirus disease (COVID-19) is characterized by pneumonia with secondary damage to multiple organs including the liver. Liver injury (elevated alanine aminotransferase [ALT] and aspartate aminotransferase [AST]) often correlates with disease severity in COVID-19 patients. The aim of this study is to identify pathological microthrombi in COVID-19 patient livers by correlating their morphology with liver injury, and examine hyperfibrinogenemia and von Willebrand factor (vWF) as mechanisms of their formation. METHODS: Forty-three post-mortem liver biopsy samples from COVID-19 patients were obtained from Papa Giovanni XXIII Hospital in Bergamo, Italy. Three morphological features of microthrombosis (sinusoidal erythrocyte aggregation [SEA], platelet microthrombi [PMT], and fibrous thrombi) were evaluated. RESULTS: We found liver sinusoidal microthrombosis in 23 COVID-19 patients (53%) was associated with a higher serum ALT and AST level compared to those without (ALT: 10-fold, p = 0.04; AST: 11-fold, p = 0.08). Of 43 livers, PMT and SEA were observed in 14 (33%) and 19 (44%) cases, respectively. Fibrous thrombi were not observed. Platelet microthrombi were associated with increased ALT (p < 0.01), whereas SEA was not (p = 0.73). In COVID-19 livers, strong vWF staining in liver sinusoidal endothelial cells was associated with significantly increased platelet adhesion (1.7-fold, p = 0.0016), compared to those with weak sinusoidal vWF (2-fold, p < 0.0001). Sinusoidal erythrocyte aggregation in 19 (83%) liver samples was mainly seen in zone 2. Livers with SEA had significantly higher fibrinogen (1.6-fold, p = 0.031) compared to those without SEA in COVID-19 patients. CONCLUSIONS: Liver PMT is a pathologically important thrombosis associated with liver injury in COVID-19, while SEA is a unique morphological feature of COVID-19 patient livers. Sinusoidal vWF and hyperfibrinogenemia could contribute to PMT and SEA formation.

Liver injury in COVID-19 and IL-6 trans-signaling-induced endotheliopathy.

BACKGROUND AND AIMS: COVID-19 is associated with liver injury and elevated interleukin-6 (IL-6). We hypothesized that IL-6 trans-signaling in liver sinusoidal endothelial cells (LSECs) leads to endotheliopathy (a proinflammatory and procoagulant state) and liver injury in COVID-19. METHODS: Coagulopathy, endotheliopathy, and alanine aminotransferase (ALT) were retrospectively analyzed in a subset (n = 68), followed by a larger cohort (n = 3,780) of patients with COVID-19. Liver histology from 43 patients with COVID-19 was analyzed for endotheliopathy and its relationship to liver injury. Primary human LSECs were used to establish the IL-6 trans-signaling mechanism. RESULTS: Factor VIII, fibrinogen, D-dimer, von Willebrand factor (vWF) activity/antigen (biomarkers of coagulopathy/endotheliopathy) were significantly elevated in patients with COVID-19 and liver injury (elevated ALT). IL-6 positively correlated with vWF antigen (p = 0.02), factor VIII activity (p = 0.02), and D-dimer (p <0.0001). On liver histology, patients with COVID-19 and elevated ALT had significantly increased vWF and platelet staining, supporting a link between liver injury, coagulopathy, and endotheliopathy. Intralobular neutrophils positively correlated with platelet (p <0.0001) and vWF (p <0.01) staining, and IL-6 levels positively correlated with vWF staining (p <0.01). IL-6 trans-signaling leads to increased expression of procoagulant (factor VIII, vWF) and proinflammatory factors, increased cell surface vWF (p <0.01), and increased platelet attachment in LSECs. These effects were blocked by soluble glycoprotein 130 (IL-6 trans-signaling inhibitor), the JAK inhibitor ruxolitinib, and STAT1/3 small-interfering RNA knockdown. Hepatocyte fibrinogen expression was increased by the supernatant of LSECs subjected to IL-6 trans-signaling. CONCLUSION: IL-6 trans-signaling drives the coagulopathy and hepatic endotheliopathy associated with COVID-19 and could be a possible mechanism behind liver injury in these patients. LAY SUMMARY: Patients with SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection often have liver injury, but why this occurs remains unknown. High levels of interleukin-6 (IL-6) and its circulating receptor, which form a complex to induce inflammatory signals, have been observed in patients with COVID-19. This paper demonstrates that the IL-6 signaling complex causes harmful changes to liver sinusoidal endothelial cells and may promote blood clotting and contribute to liver injury.

What is the normal composition of pericardial fluid?

OBJECTIVE: Biochemical and cytological pericardial fluid (PF) analysis is essentially based on the knowledge of pleural fluid composition. The aim of the present study is to identify reference intervals (RIs) for PF according to state-of-art methodological standards. METHODS: We prospectively collected and analysed the PF and venous blood of consecutive subjects undergoing elective open-heart surgery from July 2017 to October 2018. Exclusion criteria for study enrolment were evidence of pericardial diseases at preoperatory workup or at intraoperatory assessment, or any other condition that could affect PF analysis. RESULTS: The final study sample included 120 patients (median age 69 years, 83 men, 69.1%). The main findings were (1) High levels of proteins, albumin and lactate dehydrogenase (LDH), but not of glucose and cholesterol (2) High cellularity, mainly represented by mesothelial cells. RIs for pericardial biochemistry were: protein content 1.7-4.6 g/dL PF/serum protein ratio 0.29-0.83, albumin 1.19-3.06 g/dL, pericardium-to-serum albumin gradient 0.18-2.37 g/dL, LDH 141-2613 U/L, PF/serum LDH ratio 0.40-2.99, glucose 80-134 mg/dL, total cholesterol 12-69 mg/dL, PF/serum cholesterol ratio 0.07-0.51. RIs for pericardial cells by optic microscopy were: 278-5608 × 106 nucleated cells/L, 40-3790 × 106 mesothelial cells/L, 35-2210 × 106 leucocytes/L, 19-1634 × 106 lymphocytes/L. CONCLUSIONS: PF is rich in nucleated cells, protein, albumin, LDH, at levels consistent with inflammatory exudates in other biological fluids. Physicians should stop to interpret PF as exudate or transudate according to tools not validated for this setting.

Standardization and harmonization in hematology: Instrument alignment, quality control materials, and commutability issue.

INTRODUCTION: In the hub and spoke laboratory network, the number of hematology analyzers (HAs) within each core center has increased, and the control of HAs alignment is becoming necessary requirement to ensure analytical quality. In this scenario, HA alignment can be assessed by analyzing the same control material used for internal quality control on multiple HAs, assuming its commutability. The aim of the study was to verify the applicability of a protocol for the alignment of HAs based on control material rather than on fresh whole-blood samples. METHODS: The alignment of five HAs was evaluated for red (RBC, Hb, MCV, RET), white (WBC, NE, LY, MO, EO, BA, IG), and platelet (PLT) series parameters, following a protocol by SIBioC, using human sample (HS) and quality control material (QC), after the verification of commutability, according to the IFCC protocol. Maximum bias was derived from biological variation data. RESULTS: A complete alignment between instruments was confirmed for the majority of the parameters investigated both for HS and QC material. Partial misalignments or inconcludent results were instead evident for MCV, MO, EO, BA, and IG. Interestingly, QC material was found to be not commutable for LY, MO, and BA. CONCLUSION: The alignment of hematologic analyzers for main cell population parameters may be verified with both QC and HS, displaying consistent results and interpretation. The evaluation for some white series parameters (EO, BA, and IG) is critical, and particular attention must be paid to the values of the material used for the alignment.

A novel haemocytometric COVID-19 prognostic score developed and validated in an observational multicentre European hospital-based study.

COVID-19 induces haemocytometric changes. Complete blood count changes, including new cell activation parameters, from 982 confirmed COVID-19 adult patients from 11 European hospitals were retrospectively analysed for distinctive patterns based on age, gender, clinical severity, symptom duration, and hospital days. The observed haemocytometric patterns formed the basis to develop a multi-haemocytometric-parameter prognostic score to predict, during the first three days after presentation, which patients will recover without ventilation or deteriorate within a two-week timeframe, needing intensive care or with fatal outcome. The prognostic score, with ROC curve AUC at baseline of 0.753 (95% CI 0.723-0.781) increasing to 0.875 (95% CI 0.806-0.926) on day 3, was superior to any individual parameter at distinguishing between clinical severity. Findings were confirmed in a validation cohort. Aim is that the score and haemocytometry results are simultaneously provided by analyser software, enabling wide applicability of the score as haemocytometry is commonly requested in COVID-19 patients.

Multicentric evaluation of analytical performances digital morphology with respect to the reference methods by manual optical microscopy.

AIMS: Optical microscopic (OM) evaluation of peripheral blood (PB) cells is still a crucial step of the laboratory haematological workflow. The morphological cell analysis is time-consuming and expensive and it requires skilled operator. To address these challenges, automated image-processing systems, as digital morphology (DM), were developed in the last few years. The aim of this multicentre study, performed according to international guidelines, is to verify the analytical performance of DM compared with manual OM, the reference method. METHODS: Four hundred and ninety PB samples were evaluated. For each sample, two May Grunwald-stained and Giemsa-stained smears were performed and the morphological evaluation of cells was analysed with both DM and OM. In addition, the assessment times of both methods were recorded. RESULTS: Comparison of DM versus OM methods was assessed with Passing-Bablok and Deming fit regression analysis: slopes ranged between 0.17 for atypical, reactive lymphocytes and plasma cells (LY(AT)) and 1.24 for basophils, and the intercepts ranged between -0.09 for blasts and 0.40 for LY(AT). The Bland-Altman bias ranged between -6.5% for eosinophils and 21.8% for meta-myemielocytes. The diagnostic agreement between the two methods was 0.98. The mean of assessment times were 150 s and 250 s for DM and OM, respectively. CONCLUSION: DM shows excellent performance. Approximately only 1.6% of PB smears need the OM revision, giving advantages in terms of efficiency, standardisation and assessment time of morphological analysis of the cells. The findings of this study may provide useful information regarding the use of DM to improve the haematological workflow.

Liver histopathology in severe COVID 19 respiratory failure is suggestive of vascular alterations.

SARS2-CoV-2 breakout in Italy caused a huge number of severely ill patients with a serious increase in mortality. Although lungs seem to be the main target of the infection, very few information are available about liver involvement, possibly evocating a systemic disease. Post-mortem wedge liver biopsies from 48 patients died from severe pulmonary COVID-19 disease with respiratory failure were collected from two main hospitals in northern Italy. No patient had clinical symptoms of liver disease or signs of liver failure before and during hospitalization; for each of them liver function tests were available. All liver samples showed minimal inflammation features. Histological pictures compatible with vascular alterations were observed, characterized by increase in number of portal vein branches associated with lumen massive dilatation, partial or complete luminal thrombosis of portal and sinusoidal vessels, fibrosis of portal tract, focally markedly enlarged and fibrotic. SARS-CoV-2 was found in 15 of 22 samples tested by in situ hybridization method. Our preliminary results confirm the clinical impression that liver failure is not a main concern and this organ is not the target of significant inflammatory damage. Histopathological findings are highly suggestive for marked derangement of intrahepatic blood vessel network secondary to systemic changes induced by virus that could target not only lung parenchyma but also cardiovascular system, coagulation cascade and endothelial layer of blood vessels. It still remains unclear if the mentioned changes are directly related to virus infection or if SARS-CoV-2 triggers a series of reactions leading to striking vascular alterations.

Preliminary evaluation of a new flow cytometry method for the routine hematology workflow.

Background In a generalist laboratory, the integration of the data obtained from hematology analyzers (HAs) with those from multiparametric flow cytometry (FMC) could increase the specificity and sensitivity of first level screening to identify the pathological samples. The aim of this study was to perform a preliminary evaluation of a new simple hybrid method (HM). The method was obtained by integration between HAs reagents into FCM, with a basic monoclonal antibodies panel for the leukocytes differential count. Methods Eighty-one peripheral blood samples, collected in K3EDTA tubes, were analyzed by XN-module, and CyFlow Space System, using both standard MoAbs and HM method analysis, and with the optical microscopy (OM). Within-run imprecision was carried out using normal samples, the carryover was evaluated, data comparison was performed with Passing-Bablok regression and Bland-Altman plots. Results The within-run imprecision of HM methods ranged between 1.4% for neutrophils (NE) and 10.1% for monocytes (MO) always equal or lower to the OM. The comparison between HM methods vs. OM shows Passing-Bablok regression slopes comprised between 0.83 for lymphocyte (LY) and 1.14 for MO, whilst the intercepts ranged between -0.18 for NE and 0.25 for LY. Bland-Altman relative bias was comprised between -12.43% for NE, and 19.77% for eosinophils. In all 11 pathological samples the agreement between the methods was 100%. Conclusions The new hybrid method generates a leukocytes differential count suitable for routine clinical use and it is also useful for identifying morphological abnormalities with a reduction in cost and improvement of screening for first level hematology workflow.

Comparison between optical microscopy and automation for cytometric analysis of pericardial fluids in a cohort of adult subjects undergoing cardiac surgery.

AIMS: Limited information is available on number and type of cells present in the pericardial fluid (PF). Current evidence and has been garnered with inaccurate application of guidelines for analysis of body fluids. This study was aimed at investigating the performance of automate cytometric analysis of PF in adult subjects. METHODS: Seventy-four consecutive PF samples were analysed with Sysmex XN with a module for body fluid analysis (XN-BF) and optical microscopy (OM). The study also encompassed the assessment of limit of blank, limit of detection and limit of quantitation (LoQ), imprecision, carryover and linearity of XN-BF module. RESULTS: XN-BF parameters were compared with OM for the following cell classes: total cells (TC), leucocytes (white blood cell [WBC]), polymorphonuclear (PMN) and mononuclear (MN) cells. The relative bias were -4.5%, 71.2%, 108.2% and -47.7%, respectively. Passing and Bablok regression yielded slope comprised between 0.06 for MN and 5.8 for PMN, and intercept between 0.7 for PMN and 220.3 for MN. LoQ was comprised between 3.8×106 and 6.0×106 cells/L for WBC and PMN. Linearity was acceptable and carryover negligible. CONCLUSIONS: PF has a specific cellular composition. Overall, automated cell counting can only be suggested for total number of cells, whereas OM seems still the most reliable option for cell differentiation.

Lack of harmonization in high fluorescent cell automated counts with body fluids mode in ascitic, pleural, synovial, and cerebrospinal fluids.

INTRODUCTION: Cellular analysis in body fluids (BFs) provides important diagnostic information in various pathological settings. This study was hence aimed at comparing automated cell count obtained with Mindray BC-6800 (BC-BF) vs Sysmex XN-series (XN-BF) and evaluating other quantitative and qualitative information provided by these analyzers in ascitic (AF), pleural (PF), synovial (SF), and cerebrospinal (CSF) fluids. METHODS: Three hundred and fifty-one samples (99 AFs, 45 PFs, 75 SFs, and 132 CSFs) were analyzed in parallel with BC-BF, XN-BF, and optical microscopy (OM). The study also included the assessment of diagnostic agreement among BC-BF, XN-BF, and OM. RESULTS: The comparison of BC-BF vs XN-BF yielded slopes of Passing and Bablok regression always comprised between 0.9 and 1.0 except for EO-BF and HF-BF, whilst the intercepts ranged from -0.4 for MN-BF and 12.0 for PMN-BF. The bias was comprised between -103.3% and 67.1% for HF-BF and EO-BF, respectively. A significant bias was found for TC-BF, WBC-BF, HF-BF (negative bias) and for PMN-BF and EO-BF (positive bias). The agreement (Cohen's kappa) between XN-BF and BC-BF was always ≥0.7, ranging between 0.87 in CSFs and 0.94 in AFs, and that with OM was similar (ie, 0.85 and 0.96). CONCLUSION: The cytometric analysis of BF samples using BC-BF and XN-BF is clinically favorable when appropriately combined with OM. Quantitative and qualitative parameters displayed optimal agreement, whilst instrument-specific cut-offs should be defined and implemented for HF-BF and EO-BF. Further efforts should be made for achieving better harmonization in cytometric analysis of BF samples.

A Preliminary Proposal for Quality Control Assessment and Harmonization of Leukocytes Morphology-structural Parameters (cell Population Data Parameters).

BACKGROUND: The cell population data (CPD) measured by Sysmex XN-9000 can be used for screening many hematological and non-hematological disorders. Since little information is available on harmonization of CPD among different instrumentation and clinical laboratories, this study aimed at assessing the current degree of CPD harmonization between separate Sysmex XN modules allocated to the same laboratory. METHODS: A total number of 78291 data were used for verification of within-run imprecision, analyzers harmonization, reference ranges and assessment of blood sample stability of CPD parameters, including results of daily quality control testing and those generated in samples collected from blood donors and healthy volunteers. RESULTS: Within-run imprecision of CPD parameters ranged between 0.4 and 14.1%. Good agreement was found among five different XN-modules, especially when values were adjusted after calculation of instrument-specific alignment factors. The bias of all parameters remained always lower than the reference change values in samples stored for up to 8 hours, regardless of storage temperature. CONCLUSIONS: The imprecision of CPD parameters was acceptable, except for those reflecting the dispersion of cellular clusters. Due to the lack of reference control materials, we showed that the use of data generated on a large number of normal routine samples (i.e., a Moving Average population) may be a reliable approach for testing analyzers harmonization. Nevertheless, availability of both calibration and quality control materials for these parameters is highly advisable in the future. We finally showed that whole blood samples may be stable for up to 2-4 hours for most CPD parameters.