Clinical evaluation of the cobas® MTB-RIF/INH reagent and the cobas® 6800 for the detection of isoniazid and rifampicin resistance.

We aimed to validate the performance of a newly developed real-time PCR assay using cobas® MTB-RIF/INH reagent on the cobas® 6800 system for detecting isoniazid (INH) and rifampicin (RIF) resistance, using Japanese Mycobacterium tuberculosis (MTB) isolates. In total, 119 mock sputum specimens spiked with resistant MTB were tested using the cobas® MTB-RIF/INH reagent. The whole genomes of all MTB isolates were sequenced by MiSeq and analysed for mutations/indels causing drug resistance. All isolates were tested for phenotypic drug susceptibility, then MTB negative sputa were collected and pooled to prepare mock sputum specimens for the study. The sensitivity and specificity for INH resistance at a concentration equal to 3 × the limit of detection were 77.8% and 90.0%, respectively; those for RIF resistance were 91.8% and 93.5%, respectively. The sensitivities for INH and RIF were statistically different (P = 0.014), but not the specificities (P = 0.624). Twenty-two false-susceptible and two false-resistant results were obtained in INH; meanwhile, six false-susceptible and three false-resistant results were obtained in RIF. False-resistance for INH and RIF was mainly due to disputed mutations. The cobas® MTB-RIF/INH reagent showed better performance than other rapid molecular tests.

Detection of Anti-SARS-CoV-2 Nucleocapsid and Spike Antibodies in Patients with Coronavirus Disease 2019 in Japan.

OBJECTIVES: Coronavirus Disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Serological testing for anti-SARS-CoV-2 nucleocapsid (N) antibodies (Abs) and anti-SARS-CoV-2 spike (S) Abs is performed to detect prior COVID-19 infection. It is still controversial which antibodies are the most sensitive and specific, and which can be detected earliest after infection. Here, we evaluated the results of serological tests of anti-SARS-CoV-2 N and S Abs in Japan. METHODS: Symptomatic COVID-19 patients (n = 84) and control patients with rheumatoid arthritis (n = 93) were recruited at Tokyo National Hospital. Anti-SARS-CoV-2 N and S Abs were measured by commercial electrochemiluminescence immunoassays. RESULTS: The fraction of patients positive for anti-SARS-CoV-2 N and S Abs was highest >14 days after symptom onset. The frequency of anti-SARS-CoV-2 S Ab positivity at this time (80.4%) tended to be slightly but not significantly lower than anti-SARS-CoV-2 N Ab positivity (84.8%). Optimized cut-off levels for anti-SARS-CoV-2 N and S Ab positivity were lower than the manufacturer's recommended cut-off levels. Using multiple linear regression analyzes with anti-SARS-CoV-2 N and S Abs, we created an Ab-index with high sensitivity. CONCLUSION: To increase the sensitivity of serological diagnostic tests for COVID-19, it is suggested that both anti-SARS-CoV-2 N and S Abs should be measured and cut-off levels decreased.