Putting the 3% blood culture contamination rate benchmark to the test

The Clinical Microbiology Laboratories (CML) standards specify that blood culture contamination rates should not exceed 3%, based on a Q Probe survey3,4 in which the average contamination rate for the 700 responding hospitals was 2.9%.1

Blood culture contamination rates differ widely between institutions, but hospitals frequently exceed the 3% blood culture contamination rate benchmark.2,3 Even when hospitals do achieve the accepted rate, they are conceding to the inaccuracy of nearly one-third of their positive results. That means, about 30% of all patients who receive a positive blood culture result—and for whom treatment is thereby initiated—are put at higher risk by unnecessary care.

Compare the laboratory result distribution of ‘All Blood Cultures’ to the subset of ‘Positive Blood Cultures’

3 percent blood culture contamination rate benchmark

We would not accept a test that wrongly detects pregnancy one in three times. Why tolerate these rates from blood culture testing?


Current false positive blood culture rates are unacceptable.

When hospitals aim for the 3% blood culture contamination rate benchmark1, we hit the target but miss the point.