accuracy antigen check checking colloidal coronavirus covid-virus detection diagnosis diagnostic-aid dropper drops home-use immunochromatographic-technology kit limitations limited lysis-buffer measuring-instrument medical nasal-secretion negative-result plastic quality-control-C-line rapid rectangular result sample sampling-tube self-testing test test-cassette testing advice answer business challenge challenging choice choose concept control cross decision decisions difficult difficulty direction expertise illustration key leadership manage management negative negativity no opportunity organisation organization pencil positive positivity problem Question questionnaire right solution solve solving teamwork tick tick-box trouble troubleshoot troubleshooting uncertain uncertainty wrong yes