Monday, March 06, 2006

The latest Holly Grail Test for bacterial infection? -Procalcitonin

"Use less antibiotics" has become a common theme. Antibiotics are expensive, pneumonia is a very big ticket item for CMS and hospitals and then there is the often invoked specter of antibiotic resistant in regard to which the conventional wisdom is that overuse of antibiotics is one of the causal elements. Recently, I referenced an article that suggested that effective "education" about overuse of antibiotics might have negative health effects because of underuse.

Procalcitonin, (PCT) as the name implies, is a precursor to the thyroid hormone calcitonin. Normally this substance is found in the thyroid glands but in some conditions,notably bacterial infections-but maybe not viral-blood levels rise.

A recent paper ( reported in the Feb. issue of "Pulmonary Medicine, pg 3, " Procalcitonin can guide antibiotic use in CAP cases) explored its use in community acquired pneumonia, in which the authors claimed that one could use the test to determine duration of antibiotic therapy. For the most part, how long we treat pneumonia is a function of physician preference and reliance on expert opinion.

As a recent journal club discussion of procalcitonin's role in detecting bacterial infections pointed out, already there are a number of "yes,buts" and "howevers". PCT may not always be elevated in bacterial sepsis, and may be elevated in heart failure and cardiogenic shock and I'll bet as time goes by more conditions and medications will be found to effect blood levels.

Appropriate restraint in the enthusiasm for thinking that PCT will always paint a bright line between bacterial and viral infections is expressed in this review by two investigators who have done some of the often quoted research in this area. PCT testing may well evolve into common use as one of the diagnostic elements to consider in evaluating a patient with possible infection.

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