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

Table 3

Descriptive statistics, percentage of change, and correlation for vitamin D serum concentrations in frozen samples measured in 20 subjects at two time points 6 years apart.

		25(OH)D (nmol/L) in 1968-1969 serum	25(OH)D (nmol/L) in 1974-1975 serum	Percentage of change^a
Mean (SD)
All	20	56.3 (27.86)	68.1 (31.61)	30.7 (45.88)
End of summer	6	75.2 (29.07)
End of winter	14	48.2 (23.97)
Median
All	20	54.0	59.5
End of summer	6	70.8
End of winter	14	41.4
Range
All	20	15.0–118.0	22.6–124.8	−50.0–175.7
End of summer	6	43.1–118.0
End of winter	14	15.0–96.8

^aPercentage of change was first calculated for each individual as (level in 1974-1975 serum − level in 1968-1969 serum)/(level in 1968-1969 serum) * 100%.
^b value is given according to the Wilcoxon signed rank test.