Stability of serum placental growth factor (PlGF) and soluble fms-like tyrosine kinase 1 (sFlt-1)

Figures & data

Figure 2. Mean percentage change of serum PlGF concentration (A), sFlt-1 concentration (B) and sFlt-1/PlGF ratio (C) ±90% confidence intervals at various storage times at room temperature compared to baseline values (T0). The regression line for the instability equation is indicated in black. The horizontal red lines indicate the allowable bias (PlGF: ÷8.5 to 9.3%, sFlt-1: ÷12 to 13.6% and sFlt-1/PlGF ratio ÷15.4 to 18.2%).

Table 1. Changes in serum PlGF and sFlt-1 concentrations in samples stored at room temperature at various times compared to baseline concentrations (T0).

PlGF
Storage times	T0, n = 69	24 h, n = 40	48 h, n = 38	72 h, n = 33	96 h, n = 23	120 h, n = 10	144 h, n = 10	168 h, n = 33	192 h, n = 3
% of T0 (90% CI)	100	98.3 (96.7–99.9)	98.3 (96.3–100.2)	99.7 (97.4–102.0)	99.5 (96.5–102.4)	99.2 (94.3–104.1)	100.9 (95.4–106.3)	103.9 (101.9–105.9)	101.1 (81.9–120.2)
sFlt-1
Storage times	T0, n = 69	24 h, n = 40	48 h, n = 37	72 h, n = 32	96 h, n = 23	120 h, n = 10	144 h, n = 10	168 h, n = 33	192 h, n = 3
% of T0 (90% CI)	100	100.4 (100.2–100.7)	100.4 (100.0–100.7)	100.0 (99.7–100.4)	99.6 (99.1–100.0)	99.1 (98.1–100.2)	99.2 (98.5–99.9)	99.1 (98.6–99.6)	100.6 (95.9–105.3)
sFlt-1/PlGF ratio
Storage times	T0, n = 69	24 h, n = 40	48 h, n = 37	72 h, n = 32	96 h, n = 23	120 h, n = 10	144 h, n = 10	168 h, n = 33	192 h, n = 3
% of T0 (90% CI)	100	104.1 (102.1–106.2)	104.8 (101.8–107.8)	102.1 (99.5–104.8)	100.8 (97.8–103.7)	101.8 (95.9–107.8)	99.5 (93.3–105.6)	95.8 (93.9–97.7)	100.3 (85.1–115.6)

Allowable bias for PlGF; ÷8.5% to +9.3, for sFlt-1; ÷12% to +13.6%, and sFlt-1/PlGF ratio; ÷15.4% to +18.2%.

Data availability statement

For access to data, contact the corresponding author.