Increased B-type natriuretic peptide levels in early-onset versus late-onset preeclampsia

Background: We compared B-type natriuretic peptide (BNP) levels, clinical and laboratory findings in early-onset preeclampsia (EOP), late-onset preeclampsia (LOP) and healthy pregnant groups. Methods: We studied 40 healthy pregnant and 40 preeclamptic patients. Preeclamptics were divided in two groups, the EOP group (n = 20) and LOP group (n = 20), according to gestational age at the onset of disease. The distinction criterion for early-vs. late-onset was set as week 34 of gestation. The concentration of the BNP levels was measured by a sandwich fluorescence immunoassay. For statistical analysis of the clinical and laboratory findings non-parametric methods were applied. Results: BNP levels were higher in EOP [61.35 (36.95-93.25) pg/mL] and LOP patients [32.4 (19.15-39.2) pg/mL] than in healthy pregnant women [10.05 (6.08-16.03) pg/mL] (both p < 0.001). Furthermore, EOPs had significantly higher BNP levels as compared to LOP patients (p < 0.001). A BNP cut-off < 24.5 pg/mL had a negative-predictive value of 85.1% excluding preeclampsia. There was a significant inverse correlation between plasma BNP levels of EOP patients and sodium (p < 0.05) and total protein concentrations (p < 0.05). In the EOP group, a significant positive correlation was observed between plasma levels of BNP and hematocrit (p < 0.05), serum potassium (p < 0.05), urea (p < 0.05) and 24-h proteinuria (p < 0.05). Conclusions: BNP levels were significantly higher in EOP than in LOP patients. The cut-off value < 24.5 pg/mL seems to be a powerful discriminative indicator excluding preeclampsia. The amount of proteinuria and total protein levels correlate with the elevation of the BNP levels. In EOP the extent of proteinuria is higher than in the LOP.