SARS-CoV-2 seroprevalence and infection rate in Manila, Philippines prior to national vaccination program implementation: a repeated cross-sectional analysis.

BACKGROUND: SARS-CoV-2 seroepidemiological studies are used to guide public health decision making and to prepare for emerging infectious diseases. Disease occurrence estimates are limited in the Philippines, the country with the highest reported number of coronavirus disease-related deaths in the Western Pacific region. We aimed to estimate SARS-CoV-2 seroprevalence and infection rate among outpatient clinic attendees in Metro Manila prior to the implementation of the national coronavirus disease vaccination program. METHODS: We conducted repeated cross-sectional surveys at the animal bite clinic in San Lazaro Hospital, Manila, the Philippines across four periods, 3 months apart, between May 2020 and March 2021. Multivariable logistic regression was used to assess associations between different characteristics and infection status including seropositivity. RESULTS: In total 615 participants were enrolled, ranging from 115 to 174 per period. Seroprevalence quadrupled between the first (11.3%) and second (46.8%) periods and plateaued thereafter (third-46.0%, fourth-44.6%). Among seropositive participants, total antibody concentration was comparable throughout the first to third periods but declined between the third and fourth periods. Infection prevalence was comparable across enrollment periods (range 2.9-9.5%). Post-secondary education [aOR 0.42 (95% CI 0.26, 0.67)] was protective, and frontline work [aOR 1.81 (95% CI 1.18, 2.80)] was associated with increased odds of seropositivity. Frontline work status [aOR 2.27 (95% CI 1.10, 4.75)] and large household size [aOR 2.45 (95% CI 1.18, 5.49)] were associated with increased odds of infection. CONCLUSIONS: The quadrupling of seroprevalence over 3 months between the first and second enrollment periods coincided with the high burden of infection in Metro Manila in early 2020. Our findings suggest a limit to the rise and potential decline of population-level SARS-CoV-2 infection-induced immunity without introduction of vaccines. These results may add to our understanding of how immunity develops against emerging infectious diseases including coronaviruses.

Performance of anti-SARS-CoV-2 antibody testing in asymptomatic or mild COVID-19 patients: A retrospective study in outbreak on a cruise ship.

OBJECTIVES: A few studies on antibody testing have focused on asymptomatic or mild coronavirus disease 2019 (COVID-19) patients with low initial anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody responses. Anti-SARS-CoV-2 antibody-testing performance was evaluated using blood samples from asymptomatic or mild COVID-19 patients. METHODS: Blood samples were collected from 143 COVID-19 patients during an outbreak on a cruise ship 3 weeks after diagnosis. Simultaneously, a follow-up SARS-CoV-2 genetic test was performed. Samples stored before the COVID-19 pandemic were also used to evaluate the lateral flow immunochromatographic assay (LFA) and electrochemiluminescence immunoassay (ECLIA). Titers of anti-SARS-CoV-2 IgM and IgG antibodies against the nucleocapsid and spike proteins were measured using the enzyme-linked immunosorbent assay to confirm which antibodies were influenced on LFA- and ECLIA- false-negative result in crew-member samples. RESULTS: Sensitivity, specificity, positive-predictive, and negative-predictive values of LFA-detected IgM antibodies were 0.231, 1.000, 1.000, and 0.613, respectively; those of LFA-detected IgG antibodies were 0.483, 0.989, 0.972, and 0.601, respectively; and those of ECLIA-detected total antibodies were 0.783, 1.000, 1.000, and 0.848, respectively. All antibody titers measured using ELISA were significantly lower in blood samples with negative results than in those with positive results in both LFA and ECLIA. In the patients with negative results from the follow-up genetic testing, IgM-, IgG-, and total-antibody positivity rates were 22.9%, 47.6%, and 72.4%, respectively. CONCLUSIONS: These findings suggest that anti-SARS-CoV-2 antibody testing has lower performance in asymptomatic or mild COVID-19 patients than required in the guidelines.

The Effect of In Vitro Hemolysis on Measurement of Cell-Free DNA.

BACKGROUND: Hemolysis during blood drawing is a common cause of laboratory artifacts. Although circulating cell-free tumor DNA and fetal DNA are currently measured in routine practice, the effect of in vitro hemolysis on the measurement of cell-free DNA (cfDNA) has not been investigated. When in vitro hemolysis occurs, cellular DNA could be released from damaged white blood cells and reduce the fraction of circulating tumor DNA and fetal DNA. METHODS: Blood from healthy individuals was collected and passed through a narrow needle to cause in vitro hemolysis. Plasma was separated before and after mechanical damage, and concentrations of free hemoglobin and cfDNA of 2 reference genes were measured. RESULTS: cfDNA of 2 reference genes and free hemoglobin increased after mechanical damage. A clear correlation between cfDNA and free hemoglobin was observed. CONCLUSION: cfDNA concentrations are higher in hemolyzed plasma. Therefore, the fraction of circulating tumor DNA and fetal DNA can be underestimated in plasma hemolyzed by inappropriate blood collection techniques.

Plasmid-Mediated AmpC ß-Lactamase and Underestimation of Extended-Spectrum ß-Lactamase in Cefepime-Susceptible Elevated-Ceftazidime-MIC Enterobacteriaceae Isolates.

Phenotypic detection of extended-spectrum ß-lactamase (ESBL) is important for public health and infection control; however, plasmid-mediated AmpC ß-lactamases (pAmpCs) can interfere with the ESBL phenotyping. We focused on Enterobacteriaceae strains that were susceptible to cefepime but had a mildly elevated minimum inhibitory concentration (MIC) of ceftazidime and studied the effect of pAmpC on the ESBL phenotyping in this population. Genotyping of ESBL and pAmpC was performed on 528 clinical isolates of Escherichia coli, Klebsiella spp., and Proteus spp. with a ceftazidime MIC of ≥2 µg/mL and cefepime MIC≤8 µg/mL; these isolates were collected at Nagasaki University Hospital from January 2005 to March 2011. In this sample, 145 isolates (27.5%) tested positive for pAmpC (pAmpC group). The concordance rates of phenotypic and genotypic detection of ESBLs were 69.2% in the pAmpC group and 88.8% in the non-pAmpC group (P=0.04). pAmpC was more commonly detected in isolates with non-CTX-M genes (5/53, 9.4%) than in isolates with CTX-M genes (8/121, 6.6%). Our data suggest that the presence of pAmpC increases the false negative detection of ESBL. When ESBL phenotyping is used, the underestimation of the prevalence of ESBL producers should be taken into account.

[Diagnostic Utilities of an Automated and Standardized DNA Quantification during Cytomegalovirus Monitoring].

The accurate and standardized diagnosis of cytomegalovirus (CMV) infection is important for immunocom- promised patients. We prospectively evaluated the performance of an automated and standardized real-time polymerase chain reaction (PCR) -based DNA quantification for the detection of CMV. The results of PCR- based analysis were also compared with pp65 antigenemia (Ag) assay in the clinical records. The PCR- based analysis of 144 plasma samples from 26 patients with hematologic diseases detected CMV in 69 (48.0%) samples (range, <150-1.28 X 104 copies/mL) while Ag detected CMV in 32(22.2%) samples (range, 1-37/50,000 cells). The number of concordant samples between the two tests was 95(66.0%). There were nine patients who had an Ag-positive period sandwiched by Ag-negative periods and, in all these patients, the Ag-positive period was completely covered by PCR-positive period. These results suggest that PCR can detect CMV more sensitively than Ag. The automated and standardized PCR for detection of CMV can support the appropriate management in patients with risks of CMV infection. [Original].

[The Test Performance and the Differences between Sites of Blood Collection Using the Point of Care Testing-Enabled Blood Glucose Analyzer].

The point-of-care testing (POCT) has been widely performed as decentralized laboratory testing at the site of patient care. Antsense ROSE (ROSE), a POCT device for measurement of blood glucose, is handheld and time-saving and reduces risks of infection because disposable tips are used. In this study, we evaluated the testing performance of ROSE. This study was approved by the ethics committee of Nagasaki University Graduate School of Biomedical Sciences. Clinical blood samples were used for evaluating the reproducibility of testing, the calibration stability, the linearity of dilution, and the effects of dissolved oxygen partial pressure hematocrit, coexisting materials, and anticoagulant agents on the results of ROSE. Blood glucose values during 75g oral glucose tolerance testing (OGTT) were measured for analysis of the differences between sites of blood collection. Comparing with the automatic analyzer based on the hexokinase assay, the accuracy of blood glucose values measured by ROSE was evaluated. ROSE showed good performances in reproducibility, calibration stability, and dilution linearity. The values measured by ROSE were stable to oxygen partial pressure, hematocrit, coexisting materials, and anticoagulant agents and were correlated with those by the automatic analyzer. The values in capillary blood obtained from the ear or the finger elevated as approximately 30-70% as those in venous blood, at 0.5 and 1 hour after OGTT. The inhibitory effect by sodium fluoride (NaF) was 5-25% decrease after 24 hours. In conclusion, ROSE provides the blood glucose values accurately and is a rapid and useful device as a POCT.

An instructive case suggesting warfarin resistance which is independent on the regulation of the CYP2C9 and VKORC1 genotype.

To improve the safety and effectiveness of warfarin (WF) therapy, the initial dose trends to be practically decided based on single nucleotide polymorphism (SNP) genotyping of two genes, cytochrome P450 (CYP) 2C9 and vitamin K epoxide reductase complex1 (VKORC1). We encountered a 43-year-old female who was hospitalized for investigation and treatment because of intermittent convulsive seizures. Right brain cortical vein thrombi were confirmed by magnetic resonance imaging (MRI) scan; therefore, a 3 mg dose of WF was empirically initiated. The prothrombin time (PT), expressed as the international normalized ratio (INR), did not change at all, even when WF was increased to a dose of 11 mg/day. Direct sequence analysis revealed *3 in CYP2C9 and 3673 GA, 6484 CT, 6853 GC and 9041 GA in VKORC1, indicating that the genotypic pattern of the two genes is the responsible SNP for the moderate phenotype on WF sensitivity. Conclusively, our case may present an unknown mechanism other than the concern mentioned above.