geoffrey modest medical blogs

  The CDC just published an evaluation of the Abbott BinaxNOW rapid antigen test for SARS-CoV-2 infection at 2 community-based testing sites in Arizona (see  https://www.cdc.gov/mmwr/volumes/70/wr/mm7003e3.htm#T2_down  )   Details:  -- the BinaxNOW rapid antigen test received FDA Emergency Use Authorization      --it is advertised by Abbott as a "fast, $5, 15-minute, easy-to-use Covid-19 antigen test", and that with FDA EUA, is "ramping production to 50 million tests a month", and is the size of a credit card -- 3419 specimens were collected from people >10 yo, during November       -- age range 10-95yo, with median age 41, 7% age 10-17/55% aged 18-49/22% aged 50-64, and 16% >65yo      -- 38% male, 75% white/2% Black       -- asymptomatic 76%, symptomatic 24% with 19% having symptoms for <8 days: 11% 0-3 days, 8% 4-7 days  -- symptomatic people: 14% had a positive ...

A recent study documented the pretty high incidence of false negative PCR test results for SARS-CoV-2 after the initial infection (see  https://www.acpjournals.org/doi/10.7326/M20-1495 )   Details : -- 7 previously published studies provided data on PCR performance by time since symptom onset or SARS-CoV-2 exposure, from 1330 upper respiratory tract samples      -- most studies did serial testing and required at least one positive PCR to consider a case confirmed -- the FDA reports the specificity of PCR for SARS-CoV-2 to be 100%, though in this analysis the researchers assumed 90%, given that many studies were done outside of the US, and there might have been variability of test performance   Results : -- false-negative rates by day of infection (see upper part of graph below):      -- day 1 of infection: 100% (100%-100%)      -- day 4 of infection: 67% (27%-94%)      --  day 5 of infect...