Table 3.

Stability of plasma samples once frozen at −80°C

Parameter	Linear regression
	Slope	SE	95% CI	Slope significantly nonzero?	Intercept	SE	95% CI	Adjusted RL (%)	Time at which RL is reacheda
Lag time
All	0.414	0.898	−1.358 to 2.185	No	0.005	5.219	10.290 to 10.300	−99.995 to 100.005	11 mo
Apixaban	−3.210	3.243	−9.903 to 3.483	No	20.180	19.250	−19.540 to 59.910	−79.820 to 120.18	10 mo
Dabigatran	−1.412	1.853	−5.340 to 2.516	No	6.077	11.150	−17.560 to 29.720	−93.923 to 106.08	10 mo
Healthy	2.165	1.316	−0.504 to 4.834	No	−17.280	8.207	−33.920 to −0.632	−117.280 to 82.72	11 mo
LMWH	−0.383	2.028	−4.520 to 3.753	No	−9.564	11.810	−33.830 to 14.320	−109.564 to 90.436	10 mo
Rivaroxaban	1.453	2.485	−3.603 to 6.509	No	−0.721	13.190	−27.560 to 26.120	−100.721 to 99.279	10 mo
VKA	2.216	2.069	−1.994 to 6.426	No	9.868	11.590	−13.710 to 33.450	−90.132 to 109.87	10 mo
Time to peak
All	−1.596	0.769	−3.113 to −0.078	Yes	−3.735	4.471	−12.560 to 5.086	−103.735 to 96.265	11 mo
Apixaban	−0.031	2.089	−4.334 to 4.271	No	2.476	12.190	−22.640 to 27.590	−97.524 to 102.746	10 mo
Dabigatran	−3.204	3.012	−9.589 to 3.181	No	−21.720	18.13	−60.140 to 16.710	−121.720 to 78.280	10 mo
Healthy	−1.465	1.197	−3.892 to 0.9618	No	−17.370	7.463	−32.510 to 2.238	−117.37 to 82.630	11 mo
LMWH	−3.527	1.870	−7.342 to 0.2870	No	−3.726	10.890	−25.930 to 18.480	−103.726 to 96.274	10 mo
Rivaroxaban	−0.9155	1.585	−4.140 to 2.309	No	0.691	8.412	−16.420 to 17.810	−99.309 to 100.691	10 mo
VKA	−0.055	1.737	−3.592 to 3.483	No	7.920	9.870	−12.180 to 28.020	−92.080 to 107.920	10 mo
ETP
All	2.453	0.794	0.886 to 4.019	Yes	−4.123	4.615	−13.230 to 4.980	−104.123 to 95.877	11 mo
Apixaban	2.873	1.989	−1.191 to 6.937	No	−4.348	11.690	−28.470 to 19.770	−104.348 to 95.652	10 mo
Dabigatran	−1.850	2.721	−7.618 to 3.918	No	17.650	16.380	−17.060 to 52.360	−82.350 to 117.65	10 mo
Healthy	3.015	1.097	0.7903 to 5.240	Yes	−6.215	6.842	−20.090 to 7.661	−106.215 to 93.785	11 mo
LMWH	5.053	2.586	−0.221 to 10.330	No	−12.630	15.050	−43.330 to 18.060	−112.630 to 87.37	10 mo
Rivaroxaban	3.280	2.321	−1.441 to 8.002	No	−9.106	12.320	−34.170 to 15.950	−109.106 to 90.894	10 mo
VKA	1.697	7.429	−2.515 to 2.882	No	1.697	7.429	−13.420 to 16.810	−98.303 to 101.7	10 mo
Peak height
All	3.749	1.051	−1.675 to 5.822	Yes	−10.310	6.108	−22.360 to 1.745	−110.310 to 89.69	11 mo
Apixaban	−0.064	2.204	−4.612 to 4.484	No	−20.860	13.080	−47.860 to 6.136	−120.860 to 79.14	10 mo
Dabigatran	0.952	2.244	−3.805 to 5.708	No	11.470	13.500	−17.150 to 40.100	−88.530 to 111.47	10 mo
Healthy	3.252	0.682	1.870 to 4.634	Yes	7.126	4.250	−1.494 to 15.750	−92.874 to 107.13	11 mo
LMWH	10.950	4.141	2.506 to 19.400	Yes	−16.530	24.100	−65.690 to 32.630	−116.530 to 83.47	6 mo
Rivaroxaban	1.657	2.245	−2.911 to 6.224	No	−22.670	11.920	−46.910 to 1.573	−122.670 to 77.33	10 mo
VKA	2.904	1.591	−0.334 to 6.141	No	−10.460	8.912	−28.590 to 7.673	−110.460 to 89.54	10 mo

Abbreviations: ETP, endogenous thrombin potential; LMWH, low‐molecular‐weight heparin; VKA, vitamin K antagonists.

^aWhen the regression slope is not statistically significant (P > 0.05) from zero, this indicates parameter is not changing as a function of time and the maximum storage time is equal to T _MAX (last point of the linear regression.

When the regression slope is statistically significant (P ≤ 0.05) from zero, and the one‐sided 95% confidence limit of the regression line intersects the adjusted rejection limit before reaching T _MAX, the maximum storage time is determined as this intersection.