Comparison of Freelite and N-Latex serum free light chain assays: a critical review

Introduction: The measurement of serum free light chain (FLC) represents a fundamental aspect on the assessment of patients with monoclonal gammopathies (MG). Different analytical methods for FLC have become available with the possibility to obtain different value with a substantial impact on the assessment of patients with MG. This study aimed to evaluate FLC results obtained with two different assays and how the difference value obtained can impact in the patient's assessment. Materials and methods: Ninety-three patient serum samples that underwent analysis for FLC with two different methods, Serum Freelite (The Binding Site, Birmingham, UK) and N-Latex FLC (Siemens, Marburg, Germany), were included in this retrospective study. Statistical analysis was performed to evaluate correlation, difference, and the grade of concordance between the results obtained with the two methods. Results: Significant statistical differences between the results obtained from the two methods were found (P < 0.05). A good correlation was found (0.99 for κ FLC, 0.95 for λ FLC, and 0.94 for the κ/λ ratio, respectively). We found a weighted kappa value of 0.65 for κ/λ ratio, 0.65 for λ FLC and 0.90 for κ FLC. A positive bias found with the Bland-Altman plot mirrors overestimation of κ FLC and κ/λ ratio with Freelite compared to N-Latex, whilst a negative bias underscores underestimation of λ FLC by Freelite compared to N-Latex. Conclusion: Although in general the concordance between Freelite and N-Latex appears satisfactory, several discrepancies could be evidenced and consequently the two assays are not interchangeable

The impact of different sample matrices in delayed measurement of glucose

OBJECTIVES: This study was designed to compare glucose values in serum or lithium-heparin samples immediately centrifuged with those paired specimens collected in tubes containing Naf-KOx and centrifuged and analyzed 2.5h after collection. METHODS: Three blood samples were drawn from 20 volunteers. Blood samples collected in tubes with and clot activator and gel separator but without anticoagulant (SST) as well as those collected in tubes containing Lithium-Heparin and gel separator were centrifuged within 30min and analyzed 2h thereafter. Blood samples drawn in tubes containing the glycolysis inhibitor NaF-KOx were centrifuged after 2.5h and then analyzed. RESULTS: The glucose median value was 4.72mmol/L in SST tubes, 4.67mmol/L in lithium-heparin and 4.44mmol/L in NaF-KOx tubes. The difference between SST and lithium-heparin tubes was not statistically or clinically significant, whereas that between SST and Naf-KOx tubes was both analytically and clinically meaningful, exceeding the current quality specifications for glucose measurement. CONCLUSIONS: The rapid centrifugation of blood collected in serum or lithium-heparin tubes with gel separator is seemingly more reliable for delayed measurement of glucose compared to the use of blood tubes containing NaF-KOx

Altered lipid profile in patients with COVID-19 infection

Background: In this study, we aimed to investigate the pathological alterations of LDL-cholesterol, HDL-cholesterol, total cholesterol and triglycerides in COVID-19 patients during the acute phase of infection, and after recovery. Methods: A retrospective study was performed to examine serum levels of LDL-cholesterol, HDL-cholesterol, total cholesterol and triglycerides on 55 COVID-19 patients who were hospitalized in our center between February and April 2020. The lipid profile and the hematological parameters were analyzed in the same group of patients before (Group before) and after clinical management (Group after). The laboratory tests results were compared between these two groups, as well as with a group of healthy subjects (Healthy controls), matched for age and sex and selected among the blood donors. Results: LDL-cholesterol, HDL-cholesterol, total cholesterol levels were significantly lower in COVID-19 patients (Group before) as compared with normal subjects (P<0.0001). Comparing healthy controls and the group after, statistically significant differences were observed for all parameters except for total cholesterol (P=0.9006). Total cholesterol, HDL-cholesterol, LDL-cholesterol and triglyceride were found to be significantly higher after recovery than during the acute phase of infection (P<0.0001). C-reactive protein levels were found to be inversely correlated with those of LDL-cholesterol (rs =\u20130573, P<0.0001), total cholesterol (r=\u20130.732, P<0.0001), and HDL-cholesterol (r=\u20130.700, P<0.0001). Conclusions: The results of our study seemingly attest that lipids, especially cholesterol, may play an important role in viral replication, internalization and immune activation in patients with COVID-19 infection. Moreover, lipid abnormalities observed during and after this infection could be used for assessing indirectly the response to clinical treatment

The unexpected erythroblast: a case report

The complete blood cell count (CBC) is an essential test for diagnosis and management of a variety of hematological disturbances. Although the most recent generation of hematological analyzers generates rapid and accurate results, spurious data of white blood cells (WBC) or other parameters of the CBC can be occasionally observed and may be associated with derangement of the clinical decision making. Accurate knowledge of the advantages and limitations of the modern instrumentation is hence crucial. As a paradigmatic example, we describe here the case of incorrect identification of erythroblasts due to the presence of toxoplasma in peripheral venous blood

Preliminary assessment of the new Sysmex XN parameter Iron-Def for identifying iron deficiency

Background: Although the clinical assessment of iron status is usually based on iron stores, a rapid and accurate diagnosis of iron deficiency is challenging since ferritin is often unavailable as an urgent test and its value is frequently increased in acute phase conditions. This study was therefore aimed at evaluating the diagnostic performance of the new Sysmex XN "Iron Deficiency?" (Iron-Def) parameter for identifying patients with iron deficiency. Materials and methods: The study population consisted of 688 consecutive patients (median age: 71 years; 341 women and 347 men), referred for routine diagnostics to the Laboratory of Clinical Pathology of Lecco Hospital, Italy. A complete clinical chemistry profile and haematological testing were performed for identifying iron deficiency anaemia. Results: A significant negative correlation was found between Sysmex XN Iron-Def and ferritin, serum iron, mean cell haemoglobin concentration, mean cell haemoglobin, mean corpuscular volume and age, while a positive correlation was noted with transferrin, percentage of microcytic red cell, red blood cell count and red blood cell distribution width. The diagnostic accuracy of Iron-Def for identifying patients with a percentage of saturation of transferrin <15% (n=104) was 84%, with a sensitivity of 0.952 and specificity of 0.538. A sub-analysis of 71 patients with ferritin <20 ng/dL yielded an even better diagnostic performance (86%, with a sensitivity of 0.935 and specificity of 0.620). Discussion: Although additional confirmatory investigations would be needed, the preliminary findings of our study attest that Iron-Def may be an easy, inexpensive, rapid and reliable parameter for screening iron deficiency anaemia

Effect of delayed centrifugation of whole blood on serum samples stability

Background This study was aimed to investigate the effect of delayed centrifugation of whole blood samples on the quality of serum test results for five conventional clinical chemistry parameters and haemolysis index (HI). Methods Five aliquots of whole blood were prepared from each of 22 volunteer subjects. Aliquot 1 was immediately centrifuged and tested, aliquots 2\u20135 were centrifuged and tested after 3 h, 6 h, 12 h and 24 h of storage of whole blood at room temperature. Results variations of aspartate aminotransferase (AST), lactate dehydrogenase (LDH), potassium (K), total calcium (Ca), inorganic phosporous (iPhos) and haemolysis index (HI) were then compared with values of the baseline aliquot. Results After 3 h of storage all parameters except HI and AST exhibited modest but analytically significant variations. After 6 h of storage analytically significant variations were observed for AST, LDH, Ca and iPhos, whereas analytically significant variations were found for LDH, Ca and HI after 12 h of storage. All differences were analytically significant after 24 h of storage of whole blood at room temperature. Values exceeding the acceptable limits were observed for LDH, K and iPhos after 3 h of storage, for AST after 24 h of storage. Calcium remained stable throughout the study period. The HI displayed a considerable increase (i.e., 31.5%) after 24 h of storage. Conclusions The results of our experimental study about the impact of delayed centrifugation of whole blood specimens for obtaining serum attest that <3 h at room temperature should be considered the most appropriate time for storing samples before serum analysis

Spurious elevation of serum potassium concentration measured in samples with thrombocytosis

Background: Several factors that can lead to falsely elevated values of serum. Thrombocytosis is one of these factors, since breakage or activation of platelets during blood coagulation in vitro may lead to spurious release of potassium. The purpose of the study was to evaluate to which extent the platelet count may impact on potassium in both serum and plasma.Methods: The study population consisted of 42 subjects with platelets values comprised between 20 and 750×109/L. In each sample potassium was measured in both serum and plasma using potentiometric indirect method on the analyzer Modular P800 (Roche, Milan, Italy). Platelet count was performed with the hematological analyzer Advia 120 (Siemens, Milano, Italy).Results: Significant differences were found between potassium values in serum and in plasma. A significant correlation was also observed between serum potassium values and the platelet count in whole blood, but not with the age, sex, erythrocyte and leukocyte counts in whole blood. No similar correlation was noticed between plasma potassium and platelet count in whole blood. The frequency of hyperkalemia was also found to be higher in serum (20%) than in plasma (7%) in samples with a platelet count in whole blood >450×109/L.Conclusions: The results of this study show that platelets in the biological samples may impact on potassium measurement when exceeding 450×109/L. We henceforth suggest that potassium measurement in plasma may be more accurate than in serum, especially in subjects with thrombocytosis

Spurious elevation of serum potassium concentration measured in samples with thrombocytosis

Background: Several factors that can lead to falsely elevated values of serum. Thrombocytosis is one of these factors, since breakage or activation of platelets during blood coagulation in vitro may lead to spurious release of potassium. The purpose of the study was to evaluate to which extent the platelet count may impact on potassium in both serum and plasma.Methods: The study population consisted of 42 subjects with platelets values comprised between 20 and 750×109/L. In each sample potassium was measured in both serum and plasma using potentiometric indirect method on the analyzer Modular P800 (Roche, Milan, Italy). Platelet count was performed with the hematological analyzer Advia 120 (Siemens, Milano, Italy).Results: Significant differences were found between potassium values in serum and in plasma. A significant correlation was also observed between serum potassium values and the platelet count in whole blood, but not with the age, sex, erythrocyte and leukocyte counts in whole blood. No similar correlation was noticed between plasma potassium and platelet count in whole blood. The frequency of hyperkalemia was also found to be higher in serum (20%) than in plasma (7%) in samples with a platelet count in whole blood >450×109/L.Conclusions: The results of this study show that platelets in the biological samples may impact on potassium measurement when exceeding 450×109/L. We henceforth suggest that potassium measurement in plasma may be more accurate than in serum, especially in subjects with thrombocytosis

Evaluation of body fluid mode of Sysmex XN-9000 for white blood cell counts in cerebrospinal fluid

Background: This study was planned to evaluate the analytical performance of the novel and fully automated Sysmex XN-9000 analyzer for rapid analysis of cerebrospinal fluid (CSF) samples. Methods: Forty-four CSF samples were used for method comparison studies between Sysmex XN-9000 body fluid mode and conventional optical microscopy. The bias between data obtained with the two methods was estimated with Bland-Altman plot analysis. The analytical evaluation also included the assessment of imprecision, linearity and carry-over. Results: A good agreement was found between results obtained with Sysmex XN-9000 body fluid mode and optical microscopy. The mean bias was 1.6 7106 cells/L for total white blood cells (95% CI: 1221.8 7106 to 25.1 7106 cells/L), 1.3 7106 cells/L for polymorphonuclear cells (95% CI: 1213.9 7106 to 16.5 7106 cells/L) and 120.6 7106 cells/L for mononuclear cells (95% CI: 1221.5 7106 to 20.3 7106 cells/L). The carryover was found to be lower than 0.01% and the imprecision was lower than 5%. The XN-9000 body fluid mode was also characterized by excellent linearity in the range of values comprised between 85 7106\u20133,197 7106 cells/L, with correlation coefficients (r) always equal to 1.00 (P<0.001). Conclusions: The Sysmex XN-9000 body fluid mode displays excellent analytical performance in terms of imprecision, linearity, carry-over and comparability with conventional optical microscopy, so that it may be used as a first-line, screening technique for rapid analysis of CSF samples referred for both routine and, especially, for urgent testing

Advances in the fabrication of graphene transistors on flexible substrates

Graphene is an ideal candidate for next generation applications as a transparent electrode for electronics on plastic due to its flexibility and the conservation of electrical properties upon deformation. More importantly, its field-effect tunable carrier density, high mobility and saturation velocity make it an appealing choice as a channel material for field-effect transistors (FETs) for several potential applications. As an example, properly designed and scaled graphene FETs (Gr-FETs) can be used for flexible high frequency (RF) electronics or for high sensitivity chemical sensors. Miniaturized and flexible Gr-FET sensors would be highly advantageous for current sensors technology for in vivo and in situ applications. In this paper, we report a wafer-scale processing strategy to fabricate arrays of back-gated Gr-FETs on poly(ethylene naphthalate) (PEN) substrates. These devices present a large-area graphene channel fully exposed to the external environment, in order to be suitable for sensing applications, and the channel conductivity is efficiently modulated by a buried gate contact under a thin Al2O3 insulating film. In order to be compatible with the use of the PEN substrate, optimized deposition conditions of the Al2O3 film by plasma-enhanced atomic layer deposition (PE-ALD) at a low temperature (100 °C) have been developed without any relevant degradation of the final dielectric performance