SARS-CoV-2 Molecular Diagnostics in China.

The COVID-19 pandemic remains a significant problem involving health systems worldwide. Several diagnostic methods are reported for detecting the coronavirus in clinical, research, and public health laboratories. rRT-PCR is considered the gold standard; however, as it required skilled personnel and special equipment, rapid antigen tests have been developed and used as first-line screening. The serologic testing of antibodies can also be used to enhance the detection sensitivity and accuracy, which are used to assess the overall infection rate. This review summarizes the molecular techniques and serologic assays widely used in China and discusses the advantages and disadvantages of these techniques.

Successful treatment of a kidney transplant patient with COVID-19 and late-onset Pneumocystis jirovecii pneumonia.

BACKGROUND: Solid transplant patients are susceptible to Pneumocystis jirovecii pneumonia (PJP). While the vast majority of PJP cases occur within the first 6 months after transplantation, very few PJP cases are seen beyond 1 year post-transplantation (late-onset PJP). PJP and coronavirus disease 2019 (COVID-19, caused by infection with SARS-CoV-2) share quite a few common clinical manifestations and imaging findings, making the diagnosis of PJP often underappreciated during the current COVID-19 pandemic. To date, only 1 case of kidney transplantation who developed COVID-19 and late-onset PJP has been reported, but this patient also suffered from many other infections and died from respiratory failure and multiple organ dysfunction syndrome. A successful treatment of kidney patients with COVID-19 and late-onset PJP has not been reported. CASE PRESENTATION: We present a case of a 55-year-old male kidney transplant patient with COVID-19 who also developed late-onset PJP. He received a combined treatment strategy, including specific anti-pneumocystis therapy, symptomatic supportive therapy, adjusted immunosuppressive therapy, and use of antiviral drugs/antibiotics, ending with a favorable outcome. CONCLUSIONS: This case highlights the importance of prompt and differential diagnosis of PJP in kidney transplant patients with SARS-CoV-2 infection. Further studies are required to clarify if kidney transplant patients with COVID-19 could be prone to develop late-onset PJP and how these patients should be treated.

Clinical and inflammatory features based machine learning model for fatal risk prediction of hospitalized COVID-19 patients: results from a retrospective cohort study.

OBJECTIVES: To appraise effective predictors for COVID-19 mortality in a retrospective cohort study. METHODS: A total of 1270 COVID-19 patients, including 984 admitted in Sino French New City Branch (training and internal validation sets randomly split at 7:3 ratio) and 286 admitted in Optical Valley Branch (external validation set) of Wuhan Tongji hospital, were included in this study. Forty-eight clinical and laboratory features were screened with LASSO method. Further multi-tree extreme gradient boosting (XGBoost) machine learning-based model was used to rank importance of features selected from LASSO and subsequently constructed death risk prediction model with simple-tree XGBoost model. Performances of models were evaluated by AUC, prediction accuracy, precision, and F1 scores. RESULTS: Six features, including disease severity, age, levels of high-sensitivity C-reactive protein (hs-CRP), lactate dehydrogenase (LDH), ferritin, and interleukin-10 (IL-10), were selected as predictors for COVID-19 mortality. Simple-tree XGBoost model conducted by these features can predict death risk accurately with >90% precision and >85% sensitivity, as well as F1 scores >0.90 in training and validation sets. CONCLUSION: We proposed the disease severity, age, serum levels of hs-CRP, LDH, ferritin, and IL-10 as significant predictors for death risk of COVID-19, which may help to identify the high-risk COVID-19 cases. KEY MESSAGES A machine learning method is used to build death risk model for COVID-19 patients. Disease severity, age, hs-CRP, LDH, ferritin, and IL-10 are death risk factors. These findings may help to identify the high-risk COVID-19 cases.

Direct Clinical Evidence Recommending the Use of Proteinase K or Dithiothreitol to Pretreat Sputum for Detection of SARS-CoV-2.

One of the primary tools for diagnosing COVID-19 is the nucleic acid-based real-time reverse transcriptase-polymerase chain reaction (RT-PCR) test performed on respiratory specimens. The detection rate of SARS-CoV-2 in lower respiratory specimens (such as sputum) is higher than that for upper respiratory specimens (such as nasal and pharyngeal swabs). However, sputum specimens are usually quite viscous, requiring a homogenization process prior to nucleic acid (NA) extraction for RT-PCR. Sputum specimens from COVID-19 and non-COVID-19 patients were treated with four commonly used reagents-saline, N-acetyl-L-cysteine (NALC), proteinase K (PK), and dithiothreitol (DTT), prior to NA extraction. These reagents were then compared for their performance in diagnosing COVID-19 in real clinical practice. The detection rate of SARS-CoV-2 in PK- or DTT-treated sputum was comparable, and higher than that in sputum treated with NALC or saline. While there was a 4.8% (1/21) false negative rate for the PK- and DTT-treated sputum, neither treatment showed any false positive cases among patients with non-COVID diseases. Moreover, sputum pretreated with saline, NALC, PK or DTT showed higher detection rates of SARS-CoV-2 as compared to pharyngeal swabs. Taken together, we provide direct evidence recommending the use of PK or DTT to pretreat sputum samples to facilitate SARS-CoV-2 detection by clinical laboratories. Moreover, our methods should help to standardize the procedure of processing sputum specimens and improve the ability to detect SARS-CoV-2 in these samples.

Characteristics and diagnosis rate of 5630 subjects receiving SARS-CoV-2 nucleic acid tests from Wuhan, China.

BACKGROUNDThe severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a novel viral pneumonia (COVID-19), which is rapidly spreading throughout the world. The positive result of nucleic acid test is a golden criterion to confirm SARS-CoV-2 infection, but the detection features remain unclear.METHODSWe performed a retrospective analysis in 5630 high-risk individuals receiving SARS-CoV-2 nucleic acid tests in Wuhan, China, and investigated their characteristics and diagnosis rates.RESULTSThe overall diagnosis rate was 34.7% (1952/5630). Male (P = 0.025) and older populations (P = 2.525 × 10-39) were at significantly higher risk of SARS-CoV-2 infection. People were generally susceptible, and most cases concentrated in people of 30-79 years. Furthermore, we investigated the association between diagnosis rate and the amount of testing in 501 subjects. Results revealed a 1.27-fold improvement (from 27.9% to 35.5%) of diagnosis rate from testing once to twice (P = 5.847 × 10-9) and a 1.43-fold improvement (from 27.9% to 39.9%) from testing once to 3 times (P = 7.797 × 10-14). More than 3 testing administrations was not helpful for further improvement. However, this improvement was not observed in subjects with pneumonia (P = 0.097).CONCLUSIONAll populations are susceptible to SARS-CoV-2 infection, and male and older-aged populations are at significantly higher risk. Increasing the amount of testing could significantly improve diagnosis rates, except for subjects with pneumonia. It is recommended to test twice in those high-risk individuals whose results are negative the first time, and performing 3 tests is better, if possible.FUNDINGThis work was supported by National Mega Project on Major Infectious Disease Prevention (no. 2017ZX10103005-007) and National Key Research and Development Program of China (no. 2018YFE0204500).

Nasopharyngeal Swabs Are More Sensitive Than Oropharyngeal Swabs for COVID-19 Diagnosis and Monitoring the SARS-CoV-2 Load.

Objective: Detection of SARS-CoV-2 by oropharyngeal swabs (OPS) and nasopharyngeal swabs (NPS) is an essential method for coronavirus disease 2019 (COVID-19) management. It is not clear how detection rate, sensitivity, and the risk of exposure for medical providers differ in two sampling methods. Methods: In this prospective study, 120 paired NPS and OPS specimens were collected from 120 inpatients with confirmed COVID-19. SARS-CoV-2 nucleic acid in swabs were detected by real-time RT-PCR. The SARS-CoV-2 detection rate, sensitivity, and viral load were analyzed with regards NPS and OPS. Sampling discomfort reported by patients was evaluated. Results: The SARS-CoV-2 detection rate was significantly higher for NPS [46.7% (56/120)] than OPS [10.0% (12/120)] (P < 0.001). The sensitivity of NPS was also significantly higher than that of OPS (P < 0.001). At the time of sampling, the time of detectable SARS-CoV-2 had a longer median duration (25.0 vs. 20.5 days, respectively) and a longer maximum duration (41 vs. 39 days, respectively) in NPS than OPS. The mean cycle threshold (Ct) value of NPS (37.8, 95% CI: 37.0-38.6) was significantly lower than that of OPS (39.4, 95% CI: 38.9-39.8) by 1.6 (95% CI 1.0-2.2, P < 0.001), indicating that the SARS-CoV-2 load was significantly higher in NPS specimens than OPS. Patient discomfort was low in both sampling methods. During NPS sampling, patients were significantly less likely to have nausea and vomit. Conclusions: NPS had significantly higher SARS-CoV-2 detection rate, sensitivity, and viral load than OPS. NPS could reduce droplets production during swabs. NPS should be recommended for diagnosing COVID-19 and monitoring SARS-CoV-2 load. Chinese Clinical Trial Registry, number: ChiCTR2000029883.

Analysis of 2019 novel coronavirus infection and clinical characteristics of outpatients: An epidemiological study from a fever clinic in Wuhan, China.

BACKGROUND: Since the outbreak of 2019 novel coronavirus (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) pneumonia, thousands of patients with fever or cough were flocked into fever clinic of designated hospitals in Wuhan, China. To date, no data have ever been reported to reflect the prevalence of coronavirus disease 2019 (COVID-19) among these outpatients. Moreover, it is almost unknown to discriminate COVID-19 and nucleic acid negative patients based on clinical features in the fever clinics. METHODS: The infectious status of SARS-CoV-2 was estimated among the outpatients. The epidemiological and clinical characteristics were compared between COVID-19 and nucleic acid negative patients. RESULTS: The nucleic acid positive rate for SARS-CoV-2 in the outpatients from our fever clinic was 67·1%, while the majority of patients with COVID-19 were mild cases. The predominant initial symptom in those patients with COVID-19 was fever (78.2%), followed by cough (15.6%). Very significantly lower number of eosinophils was characterized in patients with COVID-19 as compared with that of nucleic acid negative patients. More importantly, the proportion of subjects with eosinophil counts lower than normal levels in patients with COVID-19 was much higher than that of nucleic acid negative patients. Fever combined with bilateral ground-glass opacities in computed tomography imaging and eosinophil count below the normal level are probably a valuable indicator of COVID-19 infection in those outpatients. CONCLUSIONS: Those findings may provide critical information for the regions, such as Europe and United States that are facing the same situation as Wuhan experienced, and could be valuable to prevent those nucleic acid negative patients from misdiagnosis before antibody testing.

Clinical characteristics of 80 hospitalized frontline medical workers infected with COVID-19 in Wuhan, China.

More than 1,000 medical workers have been infected with COVID-19 in China. The 80 hospitalized patients included 57 SARS-CoV-2 confirmed and 23 clinically diagnosed. The median age was 39 years, 49 (61.25%) were women, and one patient died. The most common symptoms at onset were fever (65, 81.25%), cough (47, 58.75%), fatigue (28, 35%), myalgia (19, 23.75%), expectoration (19, 23.75%), and diarrhea (15, 18.75%). Patients of frontline medical workers at a single-center hospital showed some unique clinical and laboratory findings compared with other patients in Wuhan and outside of Wuhan. This study provides our experience for other frontline medical workers.

Comparison of nasopharyngeal and oropharyngeal swabs for SARS-CoV-2 detection in 353 patients received tests with both specimens simultaneously.

BACKGROUND: Since the outbreak of coronavirus disease (COVID-19) in Wuhan in December 2019, by March 10, 2020, a total of 80,932 confirmed cases have been reported in China. Two consecutively negative RT-PCR test results in respiratory tract specimens is required for the evaluation of discharge from hospital, and oropharyngeal swabs were the most common sample. However, false negative results occurred in the late stage of hospitalization, and avoiding false negative result is critical essential. METHODS: We reviewed the medical record of 353 patients who received tests with both specimens simultaneously, and compared the performance between nasopharyngeal and oropharyngeal swabs. RESULTS: Of the 353 patients (outpatients, 192; inpatients, 161) studied, the median age was 54 years, and 177 (50.1%) were women. Higher positive rate (positive tests/total tests) was observed in nasopharyngeal swabs than oropharyngeal swabs, especially in inpatients. Nasopharyngeal swabs from inpatients showed higher positive rate than outpatients. Nasopharyngeal swabs from male showed higher positive rate than female, especially in outpatients. Detection with both specimens slightly increased the positive rate than nasopharyngeal swab only. Moreover, the consistency between from nasopharyngeal and oropharyngeal swabs were poor (Kappa=0.308). CONCLUSION: In conclusion, our study suggests that nasopharyngeal swabs may be more suitable than oropharyngeal swab at this stage of COVID-19 outbreak.