Immune complexes can interfere with several laboratory assays, resulting in persistently positive results incongruous with the clinical findings. Treatment of serum with polyethylene glycol (PEG) can remove this interference.
Immune complexes can be formed due to:
(1) rheumatoid factor
(2) autoimmune disease
(3) heterophile antibody
Examples of analytes affected by immune complexes:
(1) macro hormones (macroprolactin, etc.)
(2) macro enzymes (macroamylasemia, etc.)
(3) macro-vitamin B12
Method:
(1) polyethylene glycol (PEG) is added to a serum sample
(2) the mixture is incubated, resulting a precipitate
(3) the sample is centrifuged
(4) the supernatant is tested, with results compared to untreated serum sample
If immune complexes are the cause of an abnormal laboratory test result, then a serum sample after treatment with polyethylene glycol should show a normal value.
