TABLE 2.

RPT and desRPT whole-blood DBS and plasma stability challenges

QC levela	Sample matrix stabilityb			Injection matrix stabilityc			Heat stability (whole-blood DBS) or freeze-thaw cycles (plasma)d
	Control mean	Treated mean	% Difference	Control mean	Treated mean	% Difference	Control mean	Treated mean	% Difference
Whole-blood DBS
RPT
Low	161	153	−4.97	156	156	−0.51	144	142	−1.32
Medium	2,670	2,554	−4.34	2,448	2,620	7.03	2,474	2,468	−0.24
High	65,320	62,780	−3.89	66,720	68,300	2.37	67,160	66,380	−1.16
desRPT
Low	149	147	−1.21	142	147	3.38	158	164	4.13
Medium	2,374	2,486	4.72	2,278	2,308	1.32	2,656	2,734	2.94
High	61,060	63,640	4.23	64,220	67,660	5.36	73,920	73,880	−0.05
Plasma
RPT
Low	131	141	7.65	130	138	6.63	148	148	0.11
Medium	2,510	2,265	−9.76	2,548	2,535	−0.52	2,635	2,435	−7.59
High	70,150	66,625	−5.02	72,550	67,650	−6.75	70,150	68,200	−2.78
desRPT
Low	137	133	−2.74	145	136	−6.59	130	135	3.85
Medium	2,743	2,605	−5.01	2,652	2,682	1.13	2,775	2,588	−6.76
High	69,400	67,800	−2.31	70,933	66,200	−6.67	69,400	69,300	−0.14

^aQC levels are defined as follows: low, 150 ng/ml; medium, 2,500 ng/ml; high, 70,000 ng/ml.

^bn = 5 for whole-blood DBS (2 days in the light at room temperature) and n = 4 for plasma (1 day in the light at room temperature).

^cn = 5 for whole-blood DBS (3 days in injection matrix on a reanalyzed curve) and n = 6 for plasma (5 days in injection matrix on a reanalyzed curve).

^dn = 5 for whole-blood DBS (1 day at 45°C with 100% humidity with samples stored in plastic bag with desiccant) and n = 4 for plasma (3 freeze-thaw cycles).