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Also known as the Lupus Band Test.
The doctor usually takes a skin biopsy from both a sun-exposed
area & an area never exposed to the sun.
The area is first injected with a local anaesthetic, then the sample
is obtained with a punch, an instrument that resembles a small cookie
cutter with a sharp circular edge that can be pushed through the
skin.
When the punch is removed, it yields a core of tissue that is cut
from its base with scissors or a scalpel.
A small scar may be left, but this fades with time.
The piece of skin is then examined at a pathology
laboratory, & stained to detect specific immune reactants
(IgG, IgM, IgA, complement 3 & fibrinogen).
A confluent stain with all five proteins implies a greater than
99 % probability of having SLE; if four proteins are present, a
95 % probability; three proteins an 86 % probability; & two
proteins a 60 % probability provided that IgG is one of the proteins.
In discoid lupus, only lesions (areas with rashes) display these
proteins.
In SLE, most sun-exposed areas & some non-sun-exposed areas
will display these proteins.
The Lupus band test can be used to confirm that a
rash is part of an immune complex-mediated reaction, which would
indicate the need for anti-inflammatory therapy.
It can also be performed when a patient with a positive ANA test,
but non-specific symptoms does not fulfill all the criteria for
SLE but the physician feels strongly that a diagnosis must be made
one way or the other in order to initiate treatment.
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