Plasma surfactant protein-B: a novel biomarker in chronic heart failure

Background - in chronic heart failure (CHF), elevated pulmonary microvascular pressure (Pmv) results in pulmonary edema. Because elevated Pmv may alter the integrity of the alveolocapillary barrier, allowing leakage of surfactant protein-B (SP-B) from the alveoli into the circulation, we aimed to determine plasma levels of SP-B in CHF and their relation to clinical status. Methods and Results - Fifty-three outpatients with CHF had plasma SP-B and N-terminal proBNP (NT-proBNP) assayed, in addition to a formalized clinical assessment at each clinic review over a period of 18 months. The control group comprised 19 normal volunteers. Plasma SP-B was elevated in CHF (P<0.001), and levels increased with New York Heart Association classification (P<0.001). SP-B correlated with objective clinical status parameters and NT-proBNP. During follow-up, major cardiovascular events occurred in patients with higher plasma SP-B (P<0.01) and NT-proBNP (P<0.05). Furthermore, on conditional logistic regression analysis, only SP-B was independently associated with CHF hospitalization (P=0.005). The 53 patients underwent a total of 210 outpatient visits. When the diuretic dosage was increased on clinical grounds, SP-B had increased 39% (P<0.001) and NT-proBNP had increased 32% (P<0.001). Conversely, at the next visit, SP-B fell 12% (P<0.001), whereas NT-proBNP fell 39% (P