Evaluation of the immune response to COVID-19 vaccine mRNA BNT162b2 and correlation with previous COVID-19 infection.

BACKGROUND: The kinetics of immune response after vaccination with mRNA-BNT162b2 (Comirnaty®) and the correlation with previous COVID-19 infection are still unclear. METHODS: Thirty-six subjects receiving mRNA-BNT162b2 were prospectively studied [10 days after the first dose (Time 1), 7 days and 16 weeks after the second dose (Time 2 and Time 3)] to determine antibody titers against nucleocapside, trimeric spike protein (TSP) and receptor-binding-domain (RBD) of the spike protein. Ten subjects had a previous COVID-19 infection not requiring hospitalization (Group 1) and 26 did not (Group 2). RESULTS: At Time 1 all subjects in Group 1 had IgG against TSP > 800 AU/mL compared to 11/26 (42.3%) in Group 2, whilst at Time 2 all subjects in both groups had > 800 AU/mL. The mean IgG against TSP titer at Time 3 was 711 AU/mL (95% CI 652-800) in Group 1 and 240 AU/mL (95% CI 112-375) in Group 2 (p < 0.0001). However, all subjects in both groups maintained antibody titers above the lower threshold limit at each time-point considered. These results were confirmed also using anti-RBD antibodiy tests. Antibodies against nucleocapside were reactive only in subjects in Group 1 and remained stable during the study period. No subject had a new onset of COVID-19 infection within 16 weeks of follow-up. CONCLUSIONS: Subjects with previous COVID-19 infection have a more rapid immune response to mRNA-BNT162b2 than others and maintained higher antibody titers during 16 weeks of follow-up. However, no new COVID-19 infection also in subjects with lower antibody titers.

Use of the reticulocyte channel warmed to 41 °C of the XN-9000 analyzer in samples with the presence of cold agglutinins

ABSTRACT Objectives The purpose of this study was to compare data obtained from the reticulocyte channel (RET channel) heated to 41 °C with those obtained from impedance channel (I-Channel) at room temperature in the samples with the mean corpuscular hemoglobin concentration (MCHC) < 370 g/L and in samples with the MCHC > 370 g/L, in the presence of cold agglutinins. Methods In this study, 60 blood samples (group 1) with the MCHC < 370 g/L (without cold agglutinins) and 78 blood samples (group 2) with the MCHC > 370 g/L (with cold agglutinins) were used to compare the two analytical channels of the XN-9000 analyzer in different preanalytical conditions. The parameters evaluated in both groups were the following: red blood cell (RBC), hemoglobin (HGB), hematocrit (HCT), mean cell volume (MCV), RBC-most frequent volume (R-MFV), mean hemoglobin concentration (MCH) and mean cellular hemoglobin concentration (MCHC). Results The results of this study showed an excellent correlation with both channels of the XN-9000 analyzer in samples with and without cold agglutinins, except for the MCHC. The bias between the values obtained in the I-channel and those obtained in the RET channel of both groups was insignificant and remained within the limits of acceptability, as reported by Ricos et al. for all considered parameters, except for MCHC. Conclusions The presence of cold agglutinins in blood samples can be detected by a spurious lowering of the RBC count and by a spurious increase in the MCHC. The RET channel represents a great opportunity to correct the RBC count in a rapid manner without preheating. However, neither methodology can completely solve the residual presence of cold agglutinins in all samples, despite the MCHC values being < 370 g/L.

Use of the reticulocyte channel warmed to 41°C of the XN-9000 analyzer in samples with the presence of cold agglutinins.

OBJECTIVES: The purpose of this study was to compare data obtained from the reticulocyte channel (RET channel) heated to 41°C with those obtained from impedance channel (I-Channel) at room temperature in the samples with the mean corpuscular hemoglobin concentration (MCHC)<370g/L and in samples with the MCHC>370g/L, in the presence of cold agglutinins. METHODS: In this study, 60 blood samples (group 1) with the MCHC<370g/L (without cold agglutinins) and 78 blood samples (group 2) with the MCHC>370g/L (with cold agglutinins) were used to compare the two analytical channels of the XN-9000 analyzer in different preanalytical conditions. The parameters evaluated in both groups were the following: red blood cell (RBC), hemoglobin (HGB), hematocrit (HCT), mean cell volume (MCV), RBC-most frequent volume (R-MFV), mean hemoglobin concentration (MCH) and mean cellular hemoglobin concentration (MCHC). RESULTS: The results of this study showed an excellent correlation with both channels of the XN-9000 analyzer in samples with and without cold agglutinins, except for the MCHC. The bias between the values obtained in the I-channel and those obtained in the RET channel of both groups was insignificant and remained within the limits of acceptability, as reported by Ricos et al. for all considered parameters, except for MCHC. CONCLUSIONS: The presence of cold agglutinins in blood samples can be detected by a spurious lowering of the RBC count and by a spurious increase in the MCHC. The RET channel represents a great opportunity to correct the RBC count in a rapid manner without preheating. However, neither methodology can completely solve the residual presence of cold agglutinins in all samples, despite the MCHC values being < 370g/L.