Table 2.
Effects of Delays in Centrifugation on Analyte Concentrations in Biospecimens
| Analyte | Concentration a (95% Confidence Interval) |
P-Value | |||
|---|---|---|---|---|---|
| 0.5 hours | 1.5 hours | 3.5 hours | 5.5 hours | ||
| ACTH (pg/mL) | 13.4 (12.8-14.1) |
13.5 (12.8-14.1) |
13.4 (12.8-14.1) |
13.2 (12.6-13.9) |
0.97 |
| IL-6 (pg/mL) | 1.29 (1.24-1.34) |
1.23 (1.19-1.28) |
1.06 (1.02-1.10) |
0.99 (0.95-1.03) |
<0.0001 |
| Free T4 (ng/dL) | 1.41 (1.37-1.46) |
1.36 (1.32-1.41) |
1.43 (1.39-1.48) |
1.41 (1.37-1.46) |
0.20 |
| % CDT | 1.83 (1.76-1.90) |
1.86 (1.79-1.93) |
1.84 (1.77-1.91) |
1.84 (1.77-1.91) |
0.98 |
| Insulin (μIU/mL) |
14.8 (14.0-15.5) |
12.7 (12.1-13.4) |
11.9 (11.3-12.5) |
11.5 (10.9-12.1) |
<0.0001 |
| IGF-1 (ng/mL) | 138.6 (133.4-144.0) |
138.9 (133.7-144.2) |
136.8 (131.7-142.0) |
146.3 (140.7-152.1) |
0.13 |
a
Concentrations are predicted geometric means for each time point and analyte.
SI unit conversion factors: ACTH, pg/mL×0.22=pmol/L; IL-6, pg/mL×0.131=IU/mL; free T4, ng/dL×12.871=pmol/L; % CDT, %×1=%; insulin, μIU/mL×6.00=pmol/L; IGF-1, ng/mL×0.131=nmol/L.