Inhibitors to PCR in blood include:
(1) heparin from anticoagulant therapy or as a sample anticoagulant (see previous section)
(2) high levels of IgG
(3) autoantibodies to nucleic acids
(4) heme or hemoglobin (from whole blood or hemolysis)
(5) high levels of urea
(6) presence of chelating agents
(7) release of lactoferrin from neutrophils
(8) bacterial proteins or polysaccharides in sepsis (or bacterial contamination of the sample)
Features seen with an inhibitor:
(1) Results are negative or less than expected level for the target.
(2) There is failure of amplification for an internal control.
(3) Expected results are seen if inhibitors are avoided, removed or inactivated.
Inhibitors in blood can be removed or avoided in a number of ways:
(1) pretreatment over a silica membrane
(2) addition of bovine serum albumin (BSA)
(3) use of heparinase
(4) removal of intact cells containing the target RNA or DNA
(5) use of agarose blocks to embed DNA
(6) magnetic bead capture
(7) use of a non-heparin anticoagulant
plus many others
