Table 1. Description of inter-assay reproducibility, reproducibility with processing delays, and short-term within-person stability experiments.

Experiment	Inter-assay reproducibility	Reproducibility with processing delays	Short-term within-person reproducibility
Participants	HPFS	Non-HPFS	HPFS
N	15	12	80 (40 healthy and 40 less healthy*)
Sample	EDTA plasma	EDTA plasma	EDTA plasma
Number of aliquots	2	3	2
Timing		(1) Processed immediately	Donated mean 9.4
	Split sample	(2) Stored 24 h at 4°C	(range 6.5 to 12.9)
		(3) Stored 48 h at 4°C	months apart
Storage conditions	Liquid nitrogen (below -150°C)	Liquid nitrogen (below -150°C)	Liquid nitrogen (below -150°C)
	for 1–2 years	for 4–5 years	for 13–14 years

HPFS = Health Professionals Follow-up Study

* As indicated by smoking status, age (≤ or > 65 years), BMI (normal weight/overweight), and/or hypertensive state.