Table 3.

Guide to assay troubleshooting.

Problem	Potential cause	Protocol step	Corrective action
Plating pattern (striping pattern, checkerboard pattern)	Dispensing cassette tip obstruction during dispensing	Cells and cells plus virus dispensing	Obtain a new dispensing cassette
	Dispenser failure	Cells and cells plus virus dispensing	QC dispensing instrument
Edge effect	Wrong incubator humidity setting	Incubation	Ensure the incubator humidity is 95%. For added humidity, incubate the plates inside a pan with dampened paper towels
Low variable signal	Loss of trypsin activity during storage	Antiviral assay setup	Re-titration of the trypsin working stock / preparation of a new stock
	Decrease in virus titer during storage	Antiviral assay setup	Re-titration of the virus stock
	Bad batch of collagen coated plates	Antiviral assay setup	Rerun in parallel with a plate from a different batch and obtain a new batch of plates