Inhibition Controls for Qualitative Real-Time PCR Assays: Are They Necessary for All Specimen Matrices?

A retrospective analysis of 386,706 specimens representing a variety of matrix types used in qualitative real-time PCR assays determined the overall inhibition rate to be 0.87% when the inhibition control was added preextraction to 5,613 specimens and 0.01% when the inhibition control was added postextraction but preamplification in 381,093 specimens. Inhibition rates of <= 1% were found for all specimen matrix types except urine and formalin-fixed, paraffin-embedded tissue.