Quick Review Cards for Medical Laboratory Science

False Positives and Negatives with

HIV-Antibody ELISA Testing

Immunology Review 408

CAUSES OF FALSE POSITIVES

Heat inactivation of serum

Repeated freezing/thawing of serum

Autoantibodies

Multiple pregnancies

Liver disease

Administration of immunoglobulins

Administration of certain vaccines

Some malignancies

CAUSES OF FALSE NEGATIVES

Blood drawn before seroconversion (window period)

Hypogammaglobulinemia

Immunosuppressive therapy

Strain of HIV not detected by assay

Technical errors

False neg infrequent. False pos more common in low-risk populations.