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Objectives. This study aimed to determine the IgM and IgG responses against severe acute respiratory syndrome coronavirus (SARS-CoV)-2 in coronavirus disease 2019 (COVID-19) patients with varying illness severities. Methods. IgM and IgG antibody levels were assessed via chemiluminescence immunoassay in 338 COVID-19 patients. Results. IgM levels increased during the first week after SARS-CoV-2 infection, peaked 2 weeks and then reduced to near-background levels in most patients. IgG was detectable after 1 week and was maintained at a high level for a long period. The positive rates of IgM and/or IgG antibody detections were not significantly different among the mild, severe and critical disease groups. Severe and critical cases had higher IgM levels than mild cases, whereas the IgG level in critical cases was lower than those in both mild and severe cases. This might be because of the high disease activity and/or a compromised immune response in critical cases. The IgM antibody levels were slightly higher in deceased patients than recovered patients, but IgG levels in these groups did not significantly differ. A longitudinal detection of antibodies revealed that IgM levels decreased rapidly in recovered patients, whereas in deceased cases, either IgM levels remained high or both IgM and IgG were undetectable during the disease course. Conclusion. Quantitative detection of IgM and IgG antibodies against SARS-CoV-2 quantitatively has potential significance for evaluating the severity and prognosis of COVID-19.

Cross-priming amplification (CPA) technology for tuberculosis diagnosis from sputum specimens was evaluated. The sensitivity of CPA from smear-and liquid culture-positive specimens was 96.9%, and that from smear-negative and liquid culture-positive specimens was 87.5%. The specificity of CPA in culture-negative specimens was 98.8%.The diagnosis of tuberculosis (TB) is based on phenotypic and genotypic methods. Light microscopy for the detection of acid-fast bacilli (AFB) in sputum smears is a rapid and specific tool commonly used all over the world, but it only detects 30% to 40% of TB patients (10). While the sensitivity of Löwen-stein-Jensen (L-J) solid or liquid culture methods is higher than that of AFB microscopy, culture-based methods require several weeks of incubation time. Several genotypic assays, mostly based on nucleic acid amplification tests, have been developed for rapid TB diagnosis, including the GenProbe amplified Mycobacterium tuberculosis direct test, Roche Amplicor MTB test, Cobas Amplicor test, Abbott LCx test, and the BD-ProbeTec (strand displacement amplification) test (1,2,5,8,12). However, the cost of equipment needed for these methods is a barrier to their widespread use, especially in developing countries. A sensitive, accurate, rapid, and affordable diagnostic tool that will work in resource-limited settings is urgently needed.Cross-priming amplification (CPA) technology is a recent invention from an isothermal DNA amplification system by Ustar Biotechnologies Co., Ltd. Using multiple cross-linked primers (six to eight primers), a DNA target sequence can be amplified at a constant temperature (Fig. 1). The detection of amplified products is performed on a lateral flow strip housed in an enclosed, sealed plastic device to prevent the leakage of amplicons (4, 7). In this study, we evaluated the CPA isothermal amplification and detection kit (Ustar Biotech, Hangzhou, China) to determine whether it could accurately detect M. tuberculosis in clinical sputum specimens from a variety of different types of patients. Sputum specimens from 180 persons who were suspected of having TB, based on their clinical symptoms and presentation, were obtained from three hospitals in Shanghai. Sputum specimens were also collected from 98 non-TB patients (with lung cancer, lung edema, and other pulmonary illnesses) presenting at the same hospitals. For comparison with the CPA assay results, all of the clinical specimens in our study were also processed for AFB smear microscopy, L-J solid medium, and BacT/Alert 3D liquid culture following standard protocols (11). Bacterial genomic DNA was extracted by boiling, as previously described (9). The CPA method was performed according to the manufacturer's instructions, using primers targeting the gyrB gene of M. tuberculosis ( Fig. 2A). The result of each CPA assay was determined by observing the presence (positive result) or absence (negative result) of visible bands on the test strips (Fig. 2B).The detection rates of mycobacteria in the 180 sputum specimens used ...

Reference values for peripheral blood lymphocyte subsets of healthy children in China To the Editor: Immunophenotyping of peripheral blood lymphocyte subsets can provide important information for the diagnosis and treatment of immunological and hematological disorders. Lymphocyte compartments undergo dramatic changes during childhood; age-matched reference values derived from healthy individuals are crucial and have been evaluated in various ethnic populations. 1-5 However, extensively detailed immunophenotyping reference values of peripheral blood lymphocytes in whole spectrum of childhood are rare. Our aim was to determine the relative and absolute numbers of lymphocyte subpopulations in healthy Chinese children from birth to age 18 years. We recruited 1075 Chinese children (604 males and 471 females) who were grouped into 7 categories according to age: group 1, 0 to 28 days; group 2, 1 to 6 months; group 3, 6 to 12 months; group 4, 1 to 4 years; group 5, 4 to 8 years; group 6, 8 to 12 years; and group 7, 12 to 18 years. Whole blood was used and staining for lymphocyte surface markers was performed after red cell lysis, according to a standard flow cytometric multicolor protocol. A total of 20 subpopulations were examined: T cells (CD45 1 SSC low CD3 1), CD4 T cells (CD45 1 SSC low CD3 1 CD4 1), CD8 T cells (CD45 1 SSC low CD3 1 CD8 1), B cells (CD45 1 SSC low CD19 1), natural killer cells (CD45 1 SSC low CD3 2 CD56 1 /CD16 1), TCRab 1 double-negative T (DNT) cells TABLE I. Distribution of the percentage of total T and B cells and their subsets by age and sex in the peripheral blood of 1075 healthy children (%) Subset Sex Group 1 0-28 d (n 5 21) Group 2 1-6 mo (n 5 104) Group 3 6-12 mo (n 5 97) Group 4 1-4 y (n 5 289) Group 5 4-8 y (n 5 271) Group 6 8-12 y (n 5 158) Group 7 12-18 y (n 5 135)