Protein test may help identify bacterial COPD exacerbations

By Mark Cowen, Senior medwireNews Reporter

Increased serum levels of pancreatic stone protein/regenerating protein (PSP/reg) may help identify bacteria-related exacerbations of chronic obstructive pulmonary disease (COPD), say researchers.

Indeed, in a study of patients presenting to an emergency department with an acute exacerbation of COPD, the team found that PSP/reg serum levels were significantly higher in patients with positive versus negative sputum bacteriology.

Using an enzyme-linked immunosorbent assay, Daiana Stolz (University Hospital Basel, Switzerland) and colleagues assessed PSP/reg levels in 108 patients with a COPD exacerbation, 133 patients with stable COPD, and 40 healthy controls.

Of the COPD patients with exacerbations, 65 tested positive and 43 negative for potentially pathogenic flora in their sputum.

The researchers found that, overall, serum PSP/reg levels were significantly higher in COPD exacerbation patients (23.8 ng/mL) than in those with stable disease (19.1 ng/mL), who, in turn, had significantly higher levels than controls (14.0 ng/mL).

In the group of COPD patients with exacerbations, those with positive sputum bacteriology had significantly higher levels than those with negative sputum bacteriology, at 26.1 versus 20.8 ng/mL.

Further analysis showed that a serum PSP/reg level of more than 18.4 ng/mL combined with the presence of discolored sputum predicted positive sputum bacteriology with a sensitivity of 92%.

"In other words, the absence of both conditions widely ruled out positive sputum cultures," says the team.

And a PSP/reg level of more than 33.9 ng/mL and discolored sputum predicted positive bacterial sputum with a specificity of 97%.

The researchers also found that elevated PSP/reg levels were associated with increased 2-year mortality among patients with COPD exacerbations.

The findings, published in Chest, suggest that "serum PSP/reg level might represent a promising new biomarker to identify bacterial etiology of COPD exacerbation," they conclude.

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