Our study identified different frequencies of inhibitors according to the nature of the clinical samples. In samples such as CSF, sera or pharynx swabs, inhibitors were identified in ,10% and ,15-20% for DNA and RNA virus detection, respectively. These values are unexpectedly high, and imply that a significant number of samples with results believed to be ''negative'' in the absence of an internal control should be considered ''unresolved''. Specific samples such as heparinized blood (72,9% of inhibitors for DNA virus detection), bone marrow (73.8% of inhibitors for DNA virus detection) and stools (36.6% and 20.8% of inhibitors for DNA and RNA viruses detection, respectively) may also benefit from the detection of inhibitors and the identification of ''unresolved'' tests.