Introduction: Placental growth factor (PlGF) is a key biomarker for diagnosing and predicting preeclampsia (PE).While serum-based PlGF assays are well established, urine has emerged as a promising non-invasive alternative matrix.However, the absence of urinary PlGF stability data remains a major preanalytical limitation.This study aimed to assess urinary PlGF stability under common preanalytical conditions, including refrigerated storage and a double freeze-thaw cycle.Materials and methods: A prospective study was conducted using urine samples from ten pregnant women.Each sample was processed under standard laboratory conditions and aliquoted into five tubes.One aliquot was immediately frozen at -80 C (T0), three were stored at 2-8 C for 48, 96, and 168 hours before freezing, and one underwent a double freeze-thaw cycle.Urinary PlGF concentrations were measured using the Elecsys PlGF immunoassay on Roche Cobas e801 analyzer.Percent degradation (PD%) was calculated relative to baseline.A linear regression model was applied to estimate the time to exceed a maximum permissible instability (MPI) of 10 %.Results: Urinary PlGF remained stable at 2-8 C for up to 48 hours, with a mean PD% of -6 % (95% confidence interval (CI): -9.1 to -2.8).The regression model (PD% = -0.0834x Time (h)) estimated the -10 % threshold at approximately 120 hours.After a double freeze-thaw cycle, the mean PD% was -1.5 % (95% CI: -3.4 to 0.4%).Conclusions: Urinary PlGF shows acceptable stability for up to 48 hours under refrigeration and is stable over two freeze-thaw cycles.These findings provide essential preanalytical data supporting its potential use in clinical and research settings.
Martinez-Marzo et al. (Thu,) studied this question.