False Positive and False Negatives in DAT and IAT Exam

Overcentrifugation and overreading

False positive

Centrifugation after incubation phase when enhancement media is used

False positive

Bacterial contamination of cells or saline OR

Dirty glassware

False positive

Saline contaminated by heavy metals or colloidal silica

False positive

Presence of fibrin in test tube (mimics agglutination)

False positive

Using serum sample for DAT

False positive

Samples collected in gel separator tubes

False positive

Specimen collected from infusion lines infused with dextrose solution

False positive

Inadequate or improper washing

False negative

Contamination of AHG by extraneous protein (glove, wrong dropper)

False negative

High concentration of IgG paraproteins in test serum

False negative

Interruption in testing and improper testing temperature

False negative

Deterioration of reagents (Improper storage)

False negative

Pro-zone and Post-zone

False negative

Low pH of saline

False negative

Inadequate incubation

False negative