Causes and Prevention of False Results
in MDx
Molecular Diagnostics
(MDx) Review 571
CAUSES PREVENTION
False positives
Contamination from other specimens
Contamination with amplicons from previous
target amplification
Environmental contamination
Contamination by testing personnel
False negatives
Inhibitors in sample, e.g., heparin, hemoglobin, lactoferrin
Degradation of nucleic acids during transport/handling
Use of plugged pipet tips & screw cap tubes to minimize sample aerosols
Use of closed tube (real-time) PCR or signal or probe amplification methods;
separate areas for sample prep & amplification with no movement of
equipment or reagents from amplification area to sample prep area; use
of dUTP-UNG system to destroy amplicons from previous amplifications
Use of 10% bleach or alcohol to clean benches, hoods; UV light to decon-
taminate sample prep areas (interferes with DNA replication by breaking
sugar-phosphate backbone)
Use of lab coats, gloves
Proper specimen collection (correct anticoagulant, no hemolysis), use of
internal control or split sample testing (1 aliquot with target added)
Use of transport media, ice, dry ice, or freezing (depending on specimen),
collection tubes designed to stabilize RNA (PAXgene Blood RNA System,
BD Diagnostics), prompt processing or preservation, inhibition of DNases
& RNases
continued...