Table 4. Pertussis toxin detection in gdPT samples unspiked and spiked with standard pertussis toxin by xCELLigence and microscopy readouts.

Sample	Experiment	Standard PT endpoint concentration (IU/mL)a		Sample endpoint concentration (μg/mL)b		Sample PT concentration (IU/μg)c		Average PT concentration (IU/μg) [IU/10 μg gdPT]d
		xCELLigence	Microscopy	xCELLigence	Microscopy	xCELLigence	Microscopy	xCELLigence	Microscopy
gdPT Unspiked	1	0.125	NT	< 50.00	NT	< 0.0025	NT	<0.0023 [<0.023]	<0.0038 [<0.038]
	2	0.094	NT	50.00	NT	0.0019	NT
	3	0.125	NT	50.00	NT	0.0025	NT
	4	0.125	0.188	50.00	<50.00	0.0025	<0.0038
	5	0.094	0.125	50.00	<50.00	0.0019	<0.0025
	6	0.125	0.250	<50.00	<50.00	<0.0025	<0.0050
gdPT Spiked (2.5 IU/mL = 16.7 ng/mL)	1	0.125	NT	6.25	NT	0.0200	NT	0.0300 [0.300]	0.0300 [0.300]
	2	0.094	NT	3.13	NT	0.0300	NT
	3	0.125	NT	3.13	NT	0.0399	NT
	4	0.125	0.188	3.13	6.25	0.0399	0.0300
	5	0.094	0.125	3.13	6.25	0.0300	0.0200
	6	0.125	0.250	6.25	6.24	0.0200	0.0400
gdPT Spiked (10 IU/mL = 66.7 ng/mL)	1	0.125	NT	1.56	NT	0.0801	NT	0.1336 [1.336]	0.1201 [1.201]
	2	0.094	NT	0.78	NT	0.1204	NT
	3	0.125	NT	0.78	NT	0.1603	NT
	4	0.125	0.188	0.78	1.56	0.1603	0.1200
	5	0.094	0.125	0.78	1.56	0.1204	0.0800
	6	0.125	0.250	0.78	1.56	0.1603	0.1603

^aMean of two replicates.

^bgdPT concentration at the highest positive dilution (≤ 65% Relative cell index by xCELLigence and ≥ 80% clustering by microscopy) at 48 h, one replicate per experiment.

^cReference standard endpoint concentration/gdPT endpoint concentration.

^d10μg of gdPT: Equivalent to one human dose. Levels of PT up to 2 IU/human dose are considered safe for humans [30,33,34].