Table 2 .

List of observed errors of use and mitigation strategies

	Potential use errors	Frequency of occurrence	Description and direct quotes from participants	Mitigation strategies
Task 1—Cartridge setup	No standard materials used	0 cases
	Damaged equipment	1 case	‘the various elements of the cartridge had come loose, and the lid had come off’ (CH2-CH3).	Leaflet for a rapid check of package content with visual
	Misplaced cartridges	0 cases	‘It can only fit the right [location] at the right time. So, if you have picked up the wrong cartridge at that point when it prompted you to put it in, it wouldn’t fit’ (CH1)	One-way interlocking components
	User forgets the correct sequence of steps	0 cases
	Reagents not stored properly	1 case	‘Reagents are expected to be stored in a fridge and this was not explained clearly during the training’ (CH2-CH3).	Support for operators: implementation of training and Instruction for use (e.g. dedicated video demonstration regarding frequent errors and malfunctions)
Task 2—insert the cartridge and initiate test	Foil lid not removed as indicated	2 cases	The aluminium foil did not remove one of the glue coverings: a small amount of glue and foil was left on the cassette. The prong got caught and it tipped it over slightly and took the casing off the prong (CH4). Unclear aluminium foil removal procedure – ‘One batch was processed without the foil being pulled back, but it seems to produce unchanged results. So, I’m not quite sure…And results were reported without the machine going into failure mode’ (CH4).	Design changes I: dye-coloured glue coverings to make residual visible; Design changes II: peeling-off symbol depicted on the aluminium foil surface; Procedure changes: Internal quality control from operators (e.g. cartridge surface cleaning with dedicated wipe).
	Premix container not locked into place	0 cases
	Fiddly parts not easily handled	0 cases
	Reduced dexterity with gloves	0 cases
	Misplaced transfer cartridges and extraction cartridges	0 cases
	Labels not visible	0 cases
	User forgets sequence of steps	1 case	Sample run twice: no warning message – ‘With the second batch [of tests], I ran into a problem. I put a sample from the same tube into the process, so where only seven samples, one of them was duplicated. As soon as I moved on to the next sample, I realised it was a mistake’ (CH4)
	The user inserts incorrect extraction lot number and reagent lot number	0 cases
	User not able to troubleshoot	1 case	Malfunctioning door closing - ‘We had a problem with the door closure of the equipment, which the engineer came and sorted it out’. (CH4)	Rapid troubleshooting guide on-screen display. Support for operators: implementation of training and Instruction for use (e.g. dedicated video demonstration regarding frequent errors and malfunctions)
	Interface not prompting correctly	1 case	Faulty message: the ‘remove the cartridge’ message appeared on screen although cartridges were correctly removed from the machine. Staff members reported splash marks and one stated ‘small splash marks on the cartridge holder which I gently wiped away with an antibacterial wipe. This worked and cleared the message and the machine continued to close the door and move on’ (CH2–CH3). The manufacturer was called, and he advised not to use alcohol-based wipes for this in future but that the response had otherwise been correct. The company did not foresee any risk of spillage.	Support for operators: implementation of training and Instruction for use (e.g. dedicated video demonstration regarding frequent errors and malfunctions)
	Interface (touch screen) not responsive	0 cases
Task 3—Test results	Reactions interrupted before it’s finished	0 cases
	Misinterpretation of test results	1 case	The same sample runs twice on POCKIT™ Central: a positive result first and a negative result subsequently were shown (CH2).	Decisional algorithm to be explored/implemented
	Results not saved appropriately	0 cases
	results failed to be exported on a USB drive	0 cases
Task 4—dispose of the material		0 cases