Higher correlation between neutralizing antibodies and surrogate neutralizing or binding antibodies in COVID-19 patients than vaccine recipients.

This study determined the seropositive rates and levels of antibodies to severe acute respiratory syndrome coronavirus-2 in 50 patients and 108 vaccinees using microneutralization test (MNT), surrogate virus neutralization test (sVNT), chemiluminescent microparticle immunoassay (CMIA), and electrochemiluminescence immunoassay (ECLIA). MNT, as the reference method, employed living clade S and Delta viruses to measure neutralizing (NT) antibodies, while sVNT employed wild type strain and Delta receptor-binding domains (RBD) as the test antigens to measure sVNT antibodies. CMIA and ECLIA employed only one version of RBD to measure the binding antibodies. Our study performed S gene sequencing of the test virus to exclude undesired mutants that might lead to changes in antibody levels in MNT assay. We showed that spike protein amino acid sequences of our Delta virus contained 13 amino acid changes, with 3 related to the reduced neutralization. The MNT assay showed a significant reduction in seropositive rates and antibody levels in the patients' sera when the Delta variant replaced clade S as the test virus. In contrast, the seropositive rates determined by sVNT assay using wild type strain RBD and Delta RBD were non-significantly different, suggesting that sVNT assay could not identify the difference between the antigenicity of wild type RBD and Delta RBD. Furthermore, the correlation between the levels of NT and sVNT antibodies was moderate with the patients' sera but modest with the post-vaccination sera. The seropositive rates in the patients, as determined by CMIA or ECLIA, were not different from the MNT assay using clade S, but not Delta, as the test virus. In all analyses, the correlations between the antibody levels measured by MNT and the other 3 assays were modest to moderate, with the r-values of 0.3500-0.7882.

A randomized comparison of hemodynamic changes in response to a heart rate-dependent phenylephrine/ephedrine protocol versus ephedrine-only for spinal hypotension during elective cesarean section.

AIM: To compare incidences of abnormal heart rate (HR) between the phenylephrine/ephedrine protocol (P/E protocol) against the ephedrine-only (C) protocol, conventionally used for treating predelivery hypotension following spinal anesthesia for cesarean section. METHODS: Two hundred and sixty-eight parturients with pre-delivery hypotension after spinal anesthesia were equally randomized to (1) Group P/E (n = 134), phenylephrine 100 mcg in 10 mL intravenously if HR ≥ 60 beats/min (bpm), or ephedrine 6 mg intravenously if HR < 60 bpm, and 2) Group C (n = 134). The primary outcome was the incidence of the parturients with abnormal HR after vasopressor administration. The secondary outcome was the mean differences of HR and hypotensive periods during the pre-delivery period. RESULTS: There was no significant difference of between-group incidences of bradycardia (12.0% in Group P/E vs 6.7% in Group C, p = 0.136) and tachycardia (26.9% vs 35.8%, p = 0.114). Mean HR was 81.9 bpm (95% confidence interval [CI] 79.9, 84.3) in Group P/E, and 88.8 bpm (86.8, 90.6) in Group C (p < 0.001). The duration of hypotension in relation to the time interval from spinal anesthesia to delivery was 20.9% (95% CI 18.4-23.2) in Group P/E, and 26.5% (23.9-29.3) in Group C (p < 0.01). The calculated area under the curve (AUC) of abnormal HR in relation to time was significantly reduced only in Group P/E (p < 0.010). CONCLUSIONS: The incidences of out-of-range HR were comparable, but the P/E protocol resulted in a lower mean HR and better control of systolic blood pressure than the ephedrine-only protocol.

Seroprevalence of anti-SARS-CoV-2 antibodies in Thai adults during the first three epidemic waves.

This study determined the presence of anti-SARS-CoV-2 antibodies in 4964 individuals, comprising 300 coronavirus disease-19 (COVID-19) prepandemic serum samples, 142 COVID-19 patients, 2113 individuals at risk due to their occupations, 1856 individuals at risk due to sharing workplaces or communities with COVID-19 patients, and 553 Thai citizens returning after spending extended periods of time in countries with a high disease prevalence. We recruited participants between May 2020 and May 2021, which spanned the first two epidemic waves and part of the third wave of the COVID-19 outbreaks in Thailand. Their sera were tested in a microneutralization and a chemiluminescence immunoassay for IgG against the N protein. Furthermore, we performed an immunofluorescence assay to resolve discordant results between the two assays. None of the prepandemic sera contained anti-SARS-CoV-2 antibodies, while antibodies developed in 88% (15 of 17) of the COVID-19 patients at 8-14 days and in 94-100% of the patients between 15 and 60 days after disease onset. Neutralizing antibodies persisted for at least 8 months, longer than IgG antibodies. Of the 2113 individuals at risk due to their occupation, none of the health providers, airport officers, or public transport drivers were seropositive, while antibodies were present in 0.44% of entertainment workers. Among the 1856 individuals at risk due to sharing workplaces or communities with COVID-19 patients, seropositivity was present in 1.9, 1.5, and 7.5% of the Bangkok residents during the three epidemic waves, respectively, and in 1.3% of the Chiang Mai people during the first epidemic wave. The antibody prevalence varied between 6.5 and 47.0% in 553 Thai people returning from high-risk countries. This serosurveillance study found a low infection rate of SARS-CoV-2 in Thailand before the emergence of the Delta variant in late May 2021. The findings support the Ministry of Public Health's data, which are based on numbers of patients and contact tracing.

Safety of Phenylephrine in Antihypotensive Treatment during Spinal Anesthesia for Cesarean Section.

OBJECTIVE: In Thailand, hypotension after spinal anesthesia for cesarean section is routinely treated by ephedrine. As incidence of fetal acidosis reportedly increases resulting from placental transfer of ephedrine, phenylephrine, an alpha-1 agonist with less lipid solubility, becomes an alternative. However, the potential development of serious bradycardia after phenylephrine is a concern. The objectives of this study were to investigate the incidence of serious bradycardia and identify risk factors associated with phenylephrine-induced serious bradycardia and other side effects of phenylephrine. MATERIAL AND METHOD: This descriptive cross-sectional study was conducted between July 1, 2014 and March 15, 2015 on 509 parturients undergoing cesarean section under spinal anesthesia. Predelivery hypotension was treated by intravenous phenylephrine 100 mcg and pretherapeutic heart rate (pHR) was recorded. If serious bradycardia (HR < 60 bpm and hypotension or HR <45 bpm) developed, atropine 0.6 mg was administered intravenously. Data were analyzed using multivariable logistic regression and AuROC. RESULTS: Incidence of serious bradycardia was 11% (95% CI: 8.0-14.0). A one bpm increment increase in pHR reduced this incidence by 4% (adjusted OR: 0.96; 95% CI: 0.94-0.98, p < 0.001; AuROC: 0.76). As compared to apHR greater than 80 bpm, apHR of 61 to 80 bpm and a pHR of 60 bpm or lower increased the risk of serious bradycardia by 3.55 times and 12.81 times, respectively. Other risk factors were height (adjusted OR: 0.94; 95% CI: 0.89-0.98, p = 0.015), baseline DBP (adjusted OR: 0.97; 95% CI: 0.94-0.99,p = 0.03), and anesthetic level at first minute (adjusted OR: 1.13; 95% CI: 1.02-1.23, p = 0.02). Benign and temporary abnormal ECG readings were noted. CONCLUSION: Phenylephrine for antihypotensive treatment in spinal anesthesia induces bradycardia. Findings indicate an association between slower HR at time phenylephrine is administered and serious bradycardia. Close ECG monitoring and prompt treatment are required.