Epidemiology Research International

Research Article

Quality Assessment of 25(OH)D, Insulin, Total Cholesterol, Triglycerides, and Potassium in 40-Year-Old Frozen Serum

Table 1

Summary of sampling strategies and laboratory methods for assessing validity of biomarkers in 40-year-old serum.


Marker		Baseline (1968-1968) analysis on fresh blood		Reanalysis 2012-2013 on frozen serum from baseline
		Period of assessment	Laboratory assessment	Sampling strategy	Laboratory assessment

Substudy I: total cholesterol, triglycerides, and potassium	26	Baseline	Automated method (Ch), semiautomated method (Tg), and flame photometry (potassium)	Random	Cobas 8000 Roche Diagnostics instrument

Substudy II: Insulin	29	≤6 months from baseline	Double antibody method	Representative of the distribution values from the baseline assessment	Sandwich-type immunoassay ECLIA method; Cobas 6000 Roche Diagnostics instrument

Substudy III: vitamin D	20	NA	NA	Representative of the summer-winter 25(OH)D variability at baseline	Roche Diagnostics vitamin D total assay and an ECLIA protein-binding assay for capturing both 25(OH)D₃ and 25(OH)D₂; Cobas e601 Roche Diagnostics instrument
				Analyses repeated on frozen serum from subsequent examination, baseline (+) 6 years

^a represents the number of subjects that were assessed both at baseline and at reanalysis (substudy I and II) or the number of subjects assessed only at reanalysis (substudy III).