Correlation of COVID-19 vaccination and RT-PCR ct value among cases in Addis Ababa, Ethiopia: implication for future preparedness.

BACKGROUND: The COVID-19 disease requires accurate diagnosis to effectively manage infection rates and disease progression. The study aims to assess the relationship between vaccination status and RT-PCR cycle threshold (Ct) values by comparing clinical, RDT and RT-PCR results. METHODS: A total of 453 suspected COVID-19 cases were included in this study. Nasopharyngeal swabs were collected for both RDT and RT-PCR testing, with RDTs conducted on-site and RT-PCR at the Ethiopian Public Health Institute (EPHI) genomics laboratory. Detailed clinical, RDT, and RT-PCR results were analyzed. Data analysis included descriptive statistics, cross-tabulation, and Chi-Square tests to investigate the connections between diagnostic outcomes and vaccination status, with a focusing on Ct values. RESULTS: RDT results showed 34.0% negative and 65.8% positive, while RT-PCR results indicated 35.8% negative and 64.2% positive cases. The discrepancies between RDT and RT-PCR results emphasize the importance of thorough testing. No significant association was found between vaccination status and viral load, as indicated by Ct values. Among RT-PCR positive cases, 49.8% had been vaccinated, suggesting challenges in interpreting results among vaccinated individuals. Further analysis revealed that vaccination (first or second dose) had minimal impact on Ct values, indicating limited influence of vaccination status on viral load dynamics in infected individuals. CONCLUSIONS: The study highlights the significant differences between RDT and RT-PCR outcomes, underscoring the need for a comprehensive testing approach. Additionally, the findings suggest that vaccination status does not significantly impact RT-PCR Ct values, complicating the interpretation of diagnostic results in vaccinated individuals, especially in breakthrough infections and potential false positives.

Comparative Analysis of HPV Detection Efficiency: Evaluating Cobas 8800 Performance in Vaginal Self-Sampling versus Clinician-Collected Samples at a Regional Thai Hospital.

BACKGROUND: This study, conducted at a regional Thai hospital, assesses the comparative efficacy of self-collected versus clinician-collected samples for HPV detection using the Cobas 8800 system among Thai women aged 30-60. METHODS: Our methodology involved analyzing 1541 self-collected and 1398 clinician-collected samples. RESULTS: The results show a statistically significant mean difference in cycle threshold (Ct) values favoring clinician-collected samples (1.53; 95% CI: 1.18-1.87, p < 0.0001). This pattern was consistent across various age groups, with the most pronounced differences noted in the oldest cohort (50-59 years), suggesting higher detection efficiency in clinician-collected samples. The study further explored the correlation of Ct values with cytological and histological outcomes, where clinician-collected samples demonstrated superior diagnostic performance, particularly in identifying LSIL and HSIL conditions, evidenced by AUC values of 0.793 and 0.866, respectively. While self-sampling remains a viable method, with sensitivity reaching up to 48.84% for LSIL and 46.15% for HSIL, clinician collection proved more accurate, likely influencing future national screening policies. CONCLUSIONS: This work underscores the need for robust sample collection methods and the importance of ongoing enhancements to self-sampling assays and techniques to ensure their efficacy in cervical cancer screening programs.

Comparison of RT-PCR cycle threshold values between individual and pooled SARS-CoV-2 infected nasopharyngeal swab specimens.

The molecular reverse transcription-polymerase chain reaction (RT-PCR) testing of respiratory tract swabs has become mandatory to confirm the diagnosis of coronavirus disease 2019 (COVID-19). However, RT-PCR tests are expensive, require standardized equipment, and relatively long testing times, and the sample pooling method has been introduced to solve this issue. The aim of this study was to compare the cycle threshold (Ct) values of the individual sample and pooled sample methods to assess how accurate the pooling method was. Repeat RT-PCR examinations were initially performed to confirm the Ct values for each sample before running the pooled test procedure. Sample extraction and amplification were performed in both assays to detect ORF1ab, N, and E genes with a cut-off point value of Ct <38. Overall, there was no difference in Ct values between individual sample and pooled sample groups at all concentrations (p=0.259) and for all pooled sizes. Only pooled size of five could detect the Ct value in the pooled samples for all concentration samples, including low-concentration sample (Ct values 36 to 38). This study highlighted that pooled RT-PCR testing strategy did not reduce the quality of individually measured RT-PCR Ct values. A pool size of five could provide a practical technique to expand the screening capacity of RT-PCR.

Clinical and laboratory predictors of mpox severity and duration: an Italian multicentre cohort study (mpox-Icona).

BACKGROUND: Severe and prolonged mpox courses have been described during the 2022-2023 outbreak. Identifying predictors of severe evolution is crucial for improving management and therapeutic strategies. We explored the predictors of mpox severity and tested the association between mpox severity and viral load in biological fluids. We also analysed the predictors of disease duration and kinetics of inflammatory markers and described the viral presence and duration of shedding in biological fluids. METHODS: This multicentre historical cohort study included adults diagnosed with laboratory-confirmed mpox diagnosis between May 2022 and September 2023 at 15 Italian centres. Patients were followed up from the day of diagnosis until clinical recovery. Biological fluids (blood, urine, saliva, and oropharyngeal and rectal swabs) were collected from each subgroup during the course of the disease and after healing. The primary outcomes were disease severity (presence of mucosal involvement, extended rash, or need for hospitalisation) and its association with the cycle threshold value (Ct-value, surrogate of viral load) in biological fluids, using standard linear and linear mixed-effect logistic regression models. Among the secondary outcomes, predictors of disease duration were assessed using a linear regression model. FINDINGS: A total of 541 patients were enrolled, including four (0.74%) women, with a median age of 38 years (IQR 33-44). Among the 235 people living with HIV (PLWH) (43.44%), 22 (4.07%) had a CD4 count lower than 350 cells/µL. Severe mpox was reported in 215 patients (39.74%). No patient died. Multivariable analysis showed that, severe mpox was more likely among Caucasians (OR 1.82; 95% CI 1.14-2.90, p = 0.012) and patients who had an onset of fever (1.95; 1.27-2.99, p = 0.002), lymphadenopathy (2.30; 1.52-3.48, p < 0.001), sore throat (2.14; 1.27-3.59, p = 0.004), and peri-anal lesions (2.91; 1.93-4.37, p < 0.001). There was a significant difference (p = 0.003) between the median Ct-value in the upper respiratory tract for patients presenting with either mild (35.15; IQR 28.77-42.01) or severe infection (31.00; 25.00-42.01). The risk of developing severe disease decreased by approximately 5% per Ct increase (0.95; 0.91-0.98; p = 0.005). The disease lasted longer in the case of proctitis (+4.78 days; 1.95-7.61, p = 0.001), sore throat (+3.12; 0.05-6.20, p = 0.046), extended rash (+3.42; 0.55-6.28, p = 0.020), as well as in PLWH with a low CD4 count (+12.51; 6.79-18.22, p < 0.001). INTERPRETATION: The identification of predictors of severe or prolonged disease and the direct association MPXV Ct-value in the upper respiratory tract and disease severity could be useful in establishing proper management and early treatment of new mpox cases. FUNDING: ICONA Foundation; Italian Ministry of Health "Ricerca Corrente Linea 2", INMI Lazzaro Spallanzani IRCCS.

Relationship between stone volume, average CT value and operation time and efficiency before ureteral soft lens laser lithotripsy.

BACKGROUND: Soft ureteroscopic holmium laser lithotripsy is becoming increasingly popular as the preferred method for treating mid-to-lower ureteral stones. Studies have indicated that the size, composition, hardness, and fragility of the stones can impact the treatment's effectiveness. OBJECTIVE: To explore the relationship between stone volume, average CT value and operation time and efficiency before ureteral soft lens laser lithotripsy. METHODS: Our study on 126 patients undergoing ureteroscopic holmium laser lithotripsy for ureteral calculi from May 2020 to January 2022 categorized them into groups based on stone volume and CT value. We compared surgical outcomes and analyzed correlations between stone characteristics, operation parameters, and stone clearance rate to identify independent risk factors influencing treatment efficacy. RESULTS: Group A demonstrated significantly shorter operation durations and lower blood loss compared to Group B, along with higher single stone clearance rates and fewer postoperative complications. Similarly, Group C exhibited shorter operation times, reduced blood loss, higher stone clearance rates, and lower complication rates than Group D. Preoperative stone volume and CT value correlated positively with operation time and stone clearance rate, with both factors identified as independent risk factors affecting ureteral stone clearance following holmium laser lithotripsy. CONCLUSION: The stone volume and average CT value before ureteral soft lens laser lithotripsy show a positive correlation with operation time and efficiency, indicating that larger stone volumes and higher CT values lead to slower lithotripsy speeds and reduced operation efficiency. Furthermore, preoperative stone volume and average CT value are identified as independent risk factors for residual stones.

The Impact of Viral Load on the Severity and Outcome Among Patients With COVID-19: A Cross-Sectional Study.

Objectives This study aimed to assess the relationship between illness severity and mortality among COVID-19 patients along with the cycle threshold (Ct) value measured by viral load. Methods A cross-sectional study was conducted based on records of the emergency room at Rashid Hospital located in Dubai, United Arab Emirates. This research was carried out on all of the appropriate records of patients who were hospitalized at Rashid Hospital in Dubai between May 2020 and January 2021. Clinical and laboratory data were used as severity indicators, and in-hospital death was designated as the outcome. Results A total of 1,633 cases were included in the analysis. The percentage of deceased patients was higher in patients with a low Ct value (11.6%) than in patients with a high Ct value (6.9%) (p-value = 0.003). Logistic analysis revealed a statistically significant correlation (OR=2.046; p-value=0.002) between mortality and viral load, as measured by the Ct value. Patients with low Ct values and aberrant laboratory findings had a higher frequency of respiratory problems and required oxygen therapy, according to clinical and laboratory markers. Conclusions A correlation was found between viral load and mortality. Advanced age, history of chronic disease, and abnormal clinical and laboratory findings were all independently linked to a greater mortality rate in COVID-19 patients, indicating that they might be utilized as predictive and prognostic factors along with the viral load.

Establishment of a predictive model of CT value in the diagnosis and differential diagnosis of pulmonary cryptococcosis.

Objective: To investigate the application value of computed tomography (CT) value (HU) in the diagnosis and differential diagnosis of pulmonary cryptococcosis (PC) and to construct a prediction model. Methods: Retrospective analysis of the clinical data of 73 patients who presented with nodular/mass-type occupations on lung CT and confirmed by histopathology in our hospital from January 2019 to May 2022 were divided into PC group (23 patients) and non-PC group (50 patients) according to the pathological findings, and the CT values of each patient's lung lesions were measured. The differences in age, gender, symptoms, lesion involvement in one/both lungs, lung lobe distribution, number of lesions, maximum lesion diameter (cm), lesion margin condition, and CT value results were compared between the two groups. Independent risk factors for PC were analyzed for indicators with statistically significant differences, clinical prediction models were constructed and column line plots were drawn, C (correction) indices were calculated, subject characteristics (ROC) curves were drawn, calibration curves and clinical decision curve analysis (DCA) were performed to further evaluate the predictive efficacy of the models. Results: Comparative analysis of patient data between the two groups showed statistically significant differences in central, peripheral and global CT values (P < 0.05), and multiple regression analysis indicated that central CT value, peripheral CT value and global CT value could be used as independent risk factors for the diagnosis and differential diagnosis of PC. The area under the ROC curve of the model predicting PC was 0.814 (95 % CI: 0.7011-0.9267), and the corrected C-index (Bootstrap = 1000) was 0.781; the actual curve overlapped well with the calibration curve; the DCA results indicated that the column line graph model has high clinical application value. Conclusions: CT value measurements of lesions can be used as an independent risk factor for PC, and clinical prediction models based on the above factors are predictive for the diagnosis and differential diagnosis of PC.

Pathogenic Role of Human Rhinovirus Mono-Infection in Pediatric Lower Respiratory Tract Infection.

Background and objective Human rhinovirus (HRV) is one of the leading causes of pediatric respiratory tract infection with a prevalence rate of 30-50%, mostly affecting children below five years of age and causing a substantial amount of economic loss. In children, it can alone or as a co-infection, cause a wide range of symptoms from mild to life-threatening ones. With the above background, the current study was carried out to emphasize the role of HRV mono-infection in pediatric acute respiratory tract infections by correlating clinical and molecular laboratory findings. Methods This study was carried out in a tertiary care teaching hospital over a duration of four years (March 2019-October 2023). Children up to 14 years of age visiting the outpatient department or admitted to the ward with diagnoses of acute respiratory tract infections (ARTIs) were included. The clinical and laboratory data were retrieved and analyzed. A nasopharyngeal swab (NPS) or throat swab (TS) was collected and sent to the Microbiology laboratory maintaining the cold chain. Nucleic acid was extracted and subjected to multiplex real-time polymerase chain reaction (RT-PCR). Result Of the 245 samples tested for the respiratory viral pathogen, 52 samples tested positive for HRV, of which 27 had HRV mono-infection. The clinico-demographic details of these 27 patients were studied in detail. The majority of the cases (24/27; 88.8%) were less than five years of age. Fever and shortness of breath were the most consistent symptoms in all. Nineteen (19/27; 62.9%) HRV mono-infection cases had underlying co-morbidities, all requiring respiratory support. The HRV mono-infection cases either developed bronchiolitis, lower respiratory tract infection, or pneumonia. All mono-infection cases had cycle threshold value (Ct) < 25, while the Ct value of HRV was > 30 in co-infection with other viruses. Conclusion Mono-infection of HRV in under-five children with underlying comorbidities and a lesser Ct value indicates severe disease manifestation and should be dealt with more cautiously.

Correlation between the thyroid computed tomography value and thyroid function in hyperthyroidism: a retrospective study.

OBJECTIVE: Radioiodine (I-131) therapy for hyperthyroidism is a well-established and safe treatment option. This study aimed to investigate the relationship between the computed tomography (CT) value and the function and volume of the thyroid gland by identifying the factors that induce changes in the CT value of patients with hyperthyroidism. METHODS: This retrospective study evaluated 38 patients with Graves' disease and 10 patients with Plummer disease. To obtain the mean CT value and volume of the thyroid gland, the entire thyroid gland was set as the region of interest. A test dose of 3.7 MBq I-131 was administered before initiating I-131 therapy, and the radioiodine uptake (RIU) rate was assessed after 3, 24, 96, and 168 h. An approximate curve was plotted based on the RIU values obtained, and the effective half-life (EHL) was calculated. The correlation between the mean CT value and the volume of the thyroid gland, 24-h RIU, EHL, and the free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), and TSH receptor antibody (TRAb) levels was evaluated. RESULTS: The CT value exhibited a significant positive correlation with EHL in patients with Graves' disease (r = 0.62, p < 0.0001) as well as patients with Plummer disease (r = 0.74, p < 0.05). However, it did not display any correlation with the remaining parameters. CONCLUSION: The CT value is significantly correlated with EHL, suggesting that it reflects thyroid function and is mainly related to the factors associated with iodine discharge.

Trends in SARS-CoV-2 cycle threshold (Ct) values from nucleic acid testing predict the trajectory of COVID-19 waves.

Forecasting COVID-19 waves helps with public health planning and resource allocation. Cycle threshold (Ct) values obtained from positive SARS-CoV-2 nucleic acid amplification test (NAAT) results offer limited value for individual patient management, but real-time analysis of temporal trends of aggregated Ct values may provide helpful information to predict the trajectories of COVID-19 waves in the community. Ct value trends on 59,609 SARS-CoV-2 NAAT-positive results from 574,403 tests using a single testing assay system, between September 2021 and January 2023, were examined to monitor the trend of the proportion of positive NAAT with lower Ct values (≤28) in relation to changing COVID-19 case numbers over time. We applied regression with autoregressive integrated moving average errors modelling approach to study the relation between Ct values and case counts. We also developed an insight product to monitor the temporal trends with Ct values obtained from SARS-CoV-2 NAAT-positive results. In this study, the proportion of lower Ct values preceded by a range of 7-32 days the rising population COVID-19 testing rate reflecting onset of a COVID-19 wave. Monitoring population Ct values may assist in predicting increased disease activity.

SARS-CoV-2 variant typing using real-time reverse transcription-polymerase chain reaction-based assays in Addis Ababa, Ethiopia.

Objectives: This study aimed to determine the SARS-CoV-2 variants in the first four COVID-19 waves using polymerase chain reaction (PCR)-based variant detection in Addis Ababa, Ethiopia. Methods: A cross-sectional study was conducted using repository nasopharyngeal samples stored at the Ethiopian Public Health Institute COVID-19 testing laboratory. Stored positive samples were randomly selected from the first four waves based on their sample collection date. A total of 641 nasopharyngeal samples were selected and re-tested for SARS-CoV-2. RNA was extracted using nucleic acid purification instrument. Then, SARS-CoV-2 detection was carried out using 10 µl RNA and 20 µl reverse transcription-PCR fluorescent mix. Cycle threshold values <38 were considered positive. Results: A total of 374 samples qualified for B.1.617 Lineage and six spike gene mutation variant typing kits. The variant typing kits identified 267 (71.4%) from the total qualifying samples. Alpha, Beta, Delta, and Omicron were dominantly identified variants from waves I, II, III, and IV, respectively. From the total identified positive study samples, 243 of 267 (91%) of variants identified from samples had cycle threshold values <30. Conclusions: The study data demonstrated that reverse transcription-PCR-based variant typing can provide additional screening opportunities where sequencing opportunity is inaccessible. The assays could be implemented in laboratories performing SARS-CoV-2 molecular testing.

Maxillary bone healing and CT value after Le Fort I osteotomy using absorbable plate system: A retrospective study.

This study aimed to evaluate maxillary bone healing and computed tomography (CT) values after Le Fort I osteotomy with sagittal split ramus osteotomy in patients with class II and III malocclusion. Four absorbable plates and screws were used to fix the maxillary segments in all patients. For 112 sides (58 patients), the bone defect areas at the anterior and posterior sites between the maxillary segments were measured using 3-dimensional CT views reconstructed over a constant CT value at 1 week and 1 year postoperatively. Subsequently, CT values at the upper, middle, and lower sites around the osteotomy line in the medial, middle, and lateral regions were measured. The bone defect area after 1 year increased at the anterior site in class III and at both the anterior and posterior sites in class II (P < 0.05). This study suggests that the increase in bone defect area was affected by lower CT values at the middle site of the middle and lateral regions in class II, and that bony defects between fragments in the maxilla could partially remain in both classes II and III within 1 year after Le Fort I osteotomy.

Vaccination Shortens the Negative Nucleic Acid Conversion Time of the Older Population: A Retrospective Cohort Study of 73,456 Asymptomatic and Mild Patients with COVID-19 in Shanghai.

Purpose: To explore the influencing factors to predict the negative nucleic acid conversion time and ORF1ab gene CT value changes in patients with asymptomatic and mild COVID-19. Patients and Methods: A total of 73,456 patients with asymptomatic and mild COVID-19 admitted to the Mobile Cabin Hospital in Shanghai from April 3 to April 23, 2022 were selected as the research objects. Epidemiological, clinical, and laboratory data were collected. Correlation analysis was performed. Results: In patients <18 years old and ≥65 years old, COVID-19 vaccine can shorten the negative nucleic acid conversion time, which is reflected in the lower median or 75% quantile (P<0.001, P<0.05). In patients with underlying diseases, the negative nucleic acid conversion time of booster vaccination and complete vaccination was lower than that of non-vaccinated group (P<0.001, P<0.05). In patients ≤18 years of age or >65 years of age, patients with comorbidity and patients with symptoms, compared with patients 18-65 years of age, patients without comorbidity and patients without symptoms, there was a greater difference in the rate of rise of CT values between vaccinated and unvaccinated patients (P<0.05). Conclusion: The time of nucleic acid conversion to negative in patients with asymptomatic and mild COVID-19 is affected by age, comorbidity, and first nucleic acid CT value. Vaccination could shorten the negative nucleic acid conversion time of the older population, those with complications or symptoms. The vaccination of older patients does not increase the risk of symptoms.

Determination of the cycle threshold value of the Xpert Xpress SARS-CoV-2/Flu/RSV test that corresponds to the presence of infectious SARS-CoV-2 in anterior nasal swabs.

Despite having high analytical sensitivities and specificities, qualitative SARS-CoV-2 nucleic acid amplification tests (NAATs) cannot distinguish infectious from non-infectious virus in clinical samples. In this study, we determined the highest cycle threshold (Ct) value of the SARS-CoV-2 targets in the Xpert Xpress SARS-CoV-2/Flu/RSV (Xpert 4plex) test that corresponded to the presence of detectable infectious SARS-CoV-2 in anterior nasal swab samples. A total of 111 individuals with nasopharyngeal swab specimens that were initially tested by the Xpert Xpress SARS-CoV-2 test were enrolled. A healthcare worker subsequently collected anterior nasal swabs from all SARS-CoV-2-positive individuals, and those specimens were tested by the Xpert 4plex test, viral culture, and laboratory-developed assays for SARS-CoV-2 replication intermediates. SARS-CoV-2 Ct values from the Xpert 4plex test were correlated with data from culture and replication intermediate testing to determine the Xpert 4plex assay Ct value that corresponded to the presence of infectious virus. Ninety-eight of the 111 (88.3%) individuals initially tested positive by the Xpert Xpress SARS-CoV-2 test. An anterior nasal swab specimen collected from positive individuals a median of 2 days later (range, 0-9 days) tested positive for SARS-CoV-2 by the Xpert 4plex test in 39.8% (39/98) of cases. Of these samples, 13 (33.3%) were considered to contain infectious virus based on the presence of cultivable virus and replication intermediates, and the highest Ct value observed for the Xpert 4plex test in these instances was 26.3. Specimens that yielded Ct values of ≤26.3 when tested by the Xpert 4plex test had a likelihood of containing infectious SARS-CoV-2; however, no infectious virus was detected in specimens with higher Ct values.IMPORTANCEUnderstanding the correlation between real-time PCR test results and the presence of infectious SARS-CoV-2 may be useful for informing patient management and workforce return-to-work or -duty. Further studies in different patient populations are needed to correlate Ct values or other biomarkers of viral replication along with the presence of infectious virus in clinical samples.

Cycle threshold values of SARS-CoV-2 RNA in conjunctival swabs and nasopharyngeal secretions: a comparative study from a tertiary care center in India.

PURPOSE: To detect the viral RNA load of SARS-CoV-2 in conjunctival swabs of COVID-19 patients, and compare with nasopharyngeal swabs. METHODS: Conjunctival swabs of COVID-19 patients (with PCR positive nasopharyngeal swabs) were subjected to quantitative reverse transcription-polymerase chain reaction (RT-PCR) for detection of SARS-CoV-2 RNA. The cycle threshold (Ct) values of Open Reading Frame 1 (ORF 1 Ab gene) and nucleoprotein (N gene) PCRs were used to assess the viral RNA load, and compare them with the baseline values of nasopharyngeal swabs. RESULTS: Of 93 patients, 17 (18.27%) demonstrated SARS-CoV-2 RNA in conjunctival swabs. Baseline nasopharyngeal swabs were collected at a median of 2 days; while, the conjunctival swabs were collected at median 7 days, from onset of illness (p < 0.001). Despite a significant delay in conjunctival swab collection than nasopharyngeal swabs, the Ct values (ORF or N gene PCRs) were comparable between nasopharyngeal swab and conjunctival swab samples. Subsequently, during the recovery period, in four of these 17 patients (with conjunctival swab positivity), when the second nasopharyngeal swab was 'negative', the conjunctival swab was 'positive'. CONCLUSION: The conjunctival swabs demonstrated SARS-CoV-2 RNA in 17 (18.27%) of 93 COVID-19 patients. Our results may suggest a delayed or a prolonged shedding of the virus/viral RNA on the ocular surface than in nasopharyngeal mucosa.

External quality assessment survey for SARS-CoV-2 nucleic acid amplification tests in clinical laboratories in Tokyo, 2021.

INTRODUCTION: Nucleic acid amplification tests (NAATs) play a pivotal role in clinical laboratories for diagnosing COVID-19. This study aimed to elucidate the accuracy of these tests. METHODS: In 2021, an external quality assessment of NAATs for SARS-CoV-2 was conducted in 47 laboratories in Tokyo, Japan. In open testing, where the laboratories knew that the samples were intended for the survey, a simulated nasopharyngeal swab suspension sample was used, featuring a positive sample A with a viral concentration of 50 copies/µL, positive sample B with 5 copies/µL, and a negative sample. Laboratories employing real-time RT-PCR were required to report cycle threshold (Ct) values. In blind testing, where the samples were processed as normal test samples, a positive sample C with 50 copies/µL was prepared using a simulated saliva sample. RESULTS: Of the 47 laboratories, 41 were engaged in open testing. For sample A, all 41 laboratories yielded positive results, whereas for sample B, 36 laboratories reported positive results, 3 laboratories reported "test decision pending", 1 laboratory reported "suspected positive", and 1 laboratory did not respond. All 41 laboratories correctly identified the negative samples as negative. The mean Ct values were 32.2 for sample A and 35.2 for sample B. In the blind test, six laboratories received samples. Sample C was identified as positive by five laboratories and negative by one laboratory. CONCLUSIONS: The nature of the specimen, specifically the saliva, may have influenced the blind test outcomes. The identified issues must be meticulously investigated and rectified to ensure accurate results.

Low usefulness of reporting tonsillar PCR Ct-values in pharyngeal infections with Fusobacterium necrophorum.

Tonsillar Fusobacterium necrophorum PCR Ct-values were higher in participants with asymptomatic tonsillar carriage than patients with pharyngeal infections. However, Ct-values were not associated with severity of disease or predictive of development of complications and hence lacked clinical usefulness. The reporting of F. necrophorum Ct-values in clinical samples is not recommended.

The sensitivity and specificity of Abbott Panbio™ COVID 19 Ag Rapid test in the context of four SARS-CoV-2 variants.

Rapid antigen tests for the detection of SARS-CoV-2 are commonly used for the diagnosis of Covid-19. Previously published data showed a wide range of sensitivity and specificity of RATs, but these studies were performed on relatively small numbers of samples and using only limited numbers of virus variants. The aim of the study was to evaluate the main parameters of a commonly used RAT for 4 different virus variants in comparison with PCR. Material and methods: A set of 2874 samples obtained from Covid-19 patients were examined both by PCR and RAT. Two commercial PCR kits (Generi Biotech, Diana Biotechnologies) and one RAT - Abbott Panbio™ COVID 19 Ag Rapid - were compared for their sensitivity and specificity in samples positive for one of the four different SARS-CoV-2 variants - B.1.258 (n = 496), Alpha (n = 645), Delta/Delta+ (n = 687), and Omicron (n = 1046). Results: The sensitivity of Panbio™ COVID19 Ag Rapid test varied from 80.0 % in Omicron to 88.92 % in Alpha variants. The specificities of the RAT for all variants reached above 93 %. Statistically significant differences were found between the results from RAT assay in select virus variants. In addition, significantly higher sensitivity (p < 0.05) was detected in samples with higher viral loads than in those with lower. Conclusion: Despite the different sensitivity and specificity of Panbio™ COVID19 Ag Rapid test (Abbott ®) for different SARS-CoV-2 variants, this test sensitivity was proven to be always above the 80 % suggested by WHO, which makes it suitable for common use, regardless of the virus variability.

A Retrospective Study on COVID-19 Infections Caused by Omicron Variant with Clinical, Epidemiological, and Viral Load Evaluations in Breakthrough Infections.

Purpose: To explore the clinical, epidemiological, and viral load characteristics of COVID-19 caused by the omicron variant. Methods: Based on the COVID-19 epidemic caused by SARS-CoV-2 Omicron BA.2 broke out in Shanghai, China. To analyze whether there is any association between clinical symptoms and viral load of COVID-19 with age, sex, and combined disease and whether the clinical symptoms and viral load are associated with vaccine-breakthrough infections. Results: The most common symptoms were cough, expectoration, and fatigue, which were more common in women than males (p < 0.001). The average viral clearance time in the > 75 years group was the longest (6.64 days). The viral load in the 60-75 years group was significantly higher than that in the other groups (p < 0.001). The 18-45 years old group had the most clinical symptoms at admission (45.39%). The days of nucleic acid-negative conversion, average viral load, highest viral load, and clinical symptoms in comorbid chronic disease patients are longer (p < 0.001). The average and highest viral loads in the unvaccinated group were longer than those in the vaccine breakthrough infection groups (p < 0.001). However, the clinical symptoms in the vaccine breakthrough infection group were significantly more severe than those in the unvaccinated group (p < 0.001). Conclusions: We found that female patients, the elderly, and those with underlying comorbidities had longer clinical positive symptoms and viral loads. Although vaccination may not reduce clinical symptoms, it can shorten the viral load and the time required for virus clearance.