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An immunochromatographic assay that has been developed for the detection of antibodies in blood-derived specimens is raising expectations for the diagnosis of COVID-19, the disease caused by the novel corona virus SARS-CoV-2 Herein, we studied the interval from symptom onset to the first positive results of the immunochromatographic assay for IgM and IgG antibodies in 52 patients with a definitive diagnosis of COVID-19 (disease confirmed by the PCR test) Furthermore, we also examined the test results in 35 patients with acute fever and pneumonia who were negative by the PCR test All patients with a definitive diagnosis of COVID-19 were confirmed to be antibody-positive The mean time from symptom onset to the first positive result for IgM antibody was 11 9 days (minimum: 5, median: 11), and that to the first positive result for IgG antibody was 11 2 days (minimum: 5, median: 11) No significant difference was observed between the tests for IgM and IgG antibodies in terms of the percentage of positive patients or the interval from first onset to the first positive test result There were no patients in whom the test for IgM became positive before the test for IgG In 45 patients (87%), both IgM and IgG became positive at the same time, and in the remaining 7 patients (13%), the test for IgG became positive before that for IgM Of 35 patients with acute fever and pneumonia who tested negative by the PCR test for SARS-CoV-2, not COVID-19, 6 (17 1%) and 1 (2 8%) showed positive results for anti-IgG antibody and anti-IgM antibody, respectively Our study results were quite limited, and we do not intend to conduct a performance evaluation of the reagents contained in the detection kits Assessment of antibody detection reagents for the immunochromatographic assay, which can be used as a complementary test to PCR, is expected in the future;however, the findings should be reviewed carefully

We experienced a 72-year-old man who developed laboratory-confirmed human coronavirus HKU1 pneumonia. PCR testing for SARS-CoV-2 from a nasopharyngeal specimen was negative twice, and rapid immunochromatographic antibody test (RIAT) using a commercially available kit for IgM and IgG against SARS-CoV-2 showed him turning positive for IgG against SARS-CoV-2. We then performed RIAT in stored serum samples from other patients who suffered laboratory-confirmed human common cold coronaviruses (n = 6) and viruses other than coronavirus (influenza virus, n = 3; rhinovirus, n = 3; metapneumovirus, n = 1; adenovirus, n = 1) admitted until January 2019. Including the present case, four of 7 (57%) showed false-positive RIAT results due to human common cold coronaviruses infection. Two of the 4 patients showed initial negative to subsequent positive RIAT results, indicating seroconversion. RIAT was positive for IgG and IgM in viruses other than coronavirus in 2 (25.0%) and 1 (12.5%) patient. Because of high incidence of false positive RIAT results, cross antigenicity between human common cold coronaviruses and SARS-CoV-2 can be considered. Results of RIAT should be interpreted in light of epidemics of human common cold coronaviruses infection. Prevalence of past SARS-CoV-2 infection may be overestimated due to high incidence of false-positive RIAT results.

To evaluate cardiac function, the regional blood flow of the subclavian artery as a parameter of cardiac output was measured instead of measuring cardiac output itself in 12 normal subjects and 17 patients with ischemic heart disease. The measurement of the subclavian arterial blood flow was continuously and noninvasively made utilizing the Doppler ultrasonic flowmeter before, during and after exercise. The exercise was performed in the upright position on a bicycle ergometer for 3 minutes at the work load of 230 Kpm/min. Delta F Ratio, that is, the ratio of the increased blood flow during the exercise to the increased blood flow during the first 3 minutes after the termination of the exercise, was calculated in all subjects. Delta F Ratio as well as the response pattern of the blood flow to exercise was investigated. In patients with ischemic heart disease, the increase in the subclavian arterial blood flow during the exercise was slow, and the time required to return to the pre-exercise level was remarkably prolonged in comparison with normal subjects. The mean delta F Ratio of the younger normal group was 7.43, and that of the older normal group was 5.53. While in patients with ischemic heart disease, markedly lower values were observed. The mean delta F Ratio of the following subgroups of patients with ischemic heart disease, the myocardial infarction group, the angina pectoris group, and the group of ischemic heart disease without pain, were 1.25, 1.97, and 2.52 respectively. The difference in the mean delta F Ratio between the older normal group and each subgroup of ischemic heart disease was statistically significant. Low delta F Ratio in patients with ischemic heart disease is supposed to be the manifestation of diminished cardiac reserve due to decreased myocardial contractility. As a simple parameter of cardiac output, the continuous measurement of the subclavian arterial blood flow by the Doppler flowmeter is a useful method for the noninvasive evaluation of cardiac function. Especially, the calculation of delta F Ratio may provide the numerical presentation of cardiac function.

The subclavian arterial blood flow as a parameter of cardiac output was measured in 7 patients with ischemic heart disease (3 acute myocardial infarction, 3 angina pectoris, 1 variant form of angina pectoris) and 5 normal subjects. The measurement was continuously and non-invasively made, utilizing the Doppler ultrasonic flowmeter technique before, during and after exercise. The exercise was performed in the upright position on a bicycle ergometer for 3 min at the work load of 230Kpm/min. In 3 normal subjects, oxygen consumption at various work loads was also measured by the Douglas bag simultaneously with the subclavian arterial blood flow.In normal subjects, the subclavian arterial blood flow steeply increased soon after the beginning of the exercise and promptly returned to the preexercise level after the termination of the exercise. While in patients with ischemic heart disease, the increase in the subclavian arterial blood flow during the exercise was slow, and the time required to return to the preexercise level was significantly prolonged. Light to moderate exercise under the work load of 230Kpm/min increased both the subclavian arterial blood flow and oxygen consumption nearly in the same ratio. With stronger exercise, the increase in oxygen consumption was by far larger than in the blood flow.Continuous measurement of the subclavian arterial blood flow by the Doppler ultrasonic technique is supposed to be a useful method for the evaluation of cardiac function.