Background Coronavirus disease 2019 (COVID-19) has become a public health emergency. The widely used reverse transcription–polymerase chain reaction (RT-PCR) method has limitations for clinical diagnosis and treatment. Methods A total of 323 samples from 76 COVID-19–confirmed patients were analyzed by droplet digital PCR (ddPCR) and RT-PCR based 2 target genes (ORF1ab and N). Nasal swabs, throat swabs, sputum, blood, and urine were collected. Clinical and imaging data were obtained for clinical staging. Results In 95 samples that tested positive by both methods, the cycle threshold (Ct) of RT-PCR was highly correlated with the copy number of ddPCR (ORF1ab gene, R2 = 0.83; N gene, R2 = 0.87). Four (4/161) negative and 41 (41/67) single-gene positive samples tested by RT-PCR were positive according to ddPCR with viral loads ranging from 11.1 to 123.2 copies/test. The viral load of respiratory samples was then compared and the average viral load in sputum (17 429 ± 6920 copies/test) was found to be significantly higher than in throat swabs (2552 ± 1965 copies/test, P < .001) and nasal swabs (651 ± 501 copies/test, P < .001). Furthermore, the viral loads in the early and progressive stages were significantly higher than that in the recovery stage (46 800 ± 17 272 vs 1252 ± 1027, P < .001) analyzed by sputum samples. Conclusions Quantitative monitoring of viral load in lower respiratory tract samples helps to evaluate disease progression, especially in cases of low viral load.

Background Few studies compared the yield of the RT-PCR assay in nasopharyngeal swabs, oropharyngeal swabs, and sputum for SARS-CoV-2 detection. Method We conducted an observational study in Beijing Ditan Hospital, China. Specimens including nasopharyngeal swabs, oropharyngeal swabs and sputum from confirmed COVID-19 patients were collected for RT-PCR testing. Disease duration was calculated from the date of symptom onset to the date of specimens’ collection and divided into three groups: ≤14days, 14-21days, and >21days. We compared positive rates across three specimens collected in different disease duration. The kappa coefficient (KC) was used to evaluate consistency of RT-PCR results between different specimens. Results A total of 291 specimens were collected and tested from 43 confirmed patients. Among specimens collected in disease duration of ≤ 14days, the positive rate was highest in sputum (79.2%), and significantly higher than that in nasopharyngeal swabs (37.5%, p=0.003) and oropharyngeal swabs (20.8%, p&0.001). Similar findings were observed in disease duration of 14-21days and >21days. The consistency of testing results between nasopharyngeal swabs and oropharyngeal swabs was low in disease duration of ≤14days and >21days. The consistency between the sputum and oropharyngeal swabs, and between the sputum and nasopharyngeal swabs were very low across all three disease durations with statistical significance. Conclusion Compared to nasopharyngeal swabs and oropharyngeal swabs, sputum had the highest yield of SARS-CoV-2 detection. Nasopharyngeal swabs and oropharyngeal swabs had a similar yield. If sputum was not feasible, a nasopharyngeal swab could be recommended for the detection of SARS-CoV-2 and early testing is needed.

The use of camptothecin and its analogues has increased in clinical settings and in agriculture. Therefore, camptothecins and their derivatives, metabolites and degradation products are frequently found in the environment. Therefore, it is important to develop an ELISA for the quantification of camptothecins in human plasma, plants, animal tissues and other matrices. The present study developed a novel competitive indirect ELISA for camptothecin using a monoclonal antibody (MAb). In total, two haptens and various carrier proteins were tested to select the most suitable immunogen for the production of MAbs against camptothecin. Hapten 1 conjugated with keyhole limpet hemocyanin was selected for the preparation of MAb 5A3, and was used to establish a competitive indirect ELISA for camptothecin. A total of three derivatives of camptothecin used in clinical practice were examined. Topotecan showed an IC 50 value of 0.68 µg/ml with a detection limit of 0.19 µg/ml, belotecan showed an IC 50 value of 0.87 µg/ml with a detection limit of 0.22 µg/ml and irinotecan showed an IC 50 value of 2.85 µg/ml with a detection limit of 0.47 µg/ml. The cross-reactivity results suggested that the assay developed in the present study possessed a high sensitivity to camptothecin. Therefore, this immunoassay technique may be suitable for monitoring the levels of camptothecin in compound analysis, clinical applications, and analyses of food and environmental samples.