Background: Pulmonary thromboembolism (PTE) occurs in a wide variety of clinical settings and presents a diagnostic challenge to clinicians, often requiring extensive imaging of the vascular bed. Management increasingly requires accurate risk stratification to rapidly identify those with massive and submassive PTE requiring different therapeutic strategies such as thrombolysis. Provision of a rapid blood test that improves diagnostic certainty and helps stratify risk could therefore bridge the gap between uncertainty and delivery of immediate early life-saving treatment.
Methods and results: One hundred and fourteen consecutive patients with suspected PTE underwent prospective evaluation. Venous blood samples were obtained from an unselected group referred for ventilation-perfusion scintigraphy. B-type natriuretic peptide (BNP), atrial natriuretic peptide (ANP) and N-terminal pro-ANP (N-ANP) were measured by radioimmunoassay using commercially available kits. The scans were classified into three groups according to standard criteria (PIOPED); normal scan (N) (n=20), low/intermediate probability (L/I) of PTE (n=77) and high probability (H) of PTE (n=17). Comparisons were also made between patients with high probability scans who died (n=3) and those who survived (n=14). Values are quoted for the median and interquartile ranges. There were statistically significant differences between groups for levels of (a) BNP (P<0.001): N=6.7 pmol/l (5.6-11.9), L/I=12.5 pmol/l (6.7-28.2) and H=18.5 pmol/l (12.6-74.6); (b) ANP (P<0.005): N=12.6 pmol/l (7.1-16.0), L/I=19.51 pmol/l (12.5-28.2) and H=19.1 pmol/l (15.7-31.7) and (c) N-ANP (P<0.05): N=177 pmol/l (119-200), L/I=302 pmol/l (152-576) and H=322 pmol/l (223-563). Levels of BNP and ANP were significantly (P<0.05) higher in patients with high probability scans and a diagnosis of PTE who died (n=3) than in those who survived (n=14); BNP: 91.6 pmol/l (77.5-336.2) vs. 14.4 pmol/l (11.9-27.4) and ANP 32.5 pmol/l (21.7-105.5) vs. 17.6 pmol/l (15.2-19.3), respectively.
Conclusions: PTE is associated with significantly elevated levels of the natriuretic peptides ANP, BNP and N-ANP. Increasing ventilation-perfusion mismatch on scintigraphy corresponds to incremental increases in the levels of ANP, BNP and N-ANP found. These peptides, and in particular BNP, may add to the diagnosis by rapidly providing a probability of PE before dedicated imaging studies can be performed. Natriuretic peptides require further study to establish their role in identifying a high-risk group who may benefit from early treatments such as thrombolysis.