Perfected by Kristiina Turjanmaa, this method for Natural Rubber Latex
Allergy testing has been used extensively for diagnosing individuals for
NRL allergy. The method involves extracting the Mutable proteins by
cutting 1 gram of glove into small pieces and soaking them at room
temperature in Sml of physiological saline for 15 minutes.
A drop of this solution is placed on the forearm, which is then pierced
by a lancet, and the resulting reaction compared to saline as a negative
control and histamine or codeine as a positive control. With new gloves
it is usual to include a known highly allergenic glove, as a reference,
in the test series. It is important that the lancet used (see diagram)
is lmm in length and has shoulders to prevent deep penetration of the
skin.
In Europe a standardized commercial NRL allergen for SPT will be
available in 1995 from Stallergenes. Currently, non-standardized
allergens are available but their sensitivity is questionable. The ALK
allergen from Denmark has a sensitivity of only 50% which means many NRL
allergic individuals will give false negatives results.
In the US, no standardized NRL allergen is available but work is
underway to remedy this. Canada currently uses the Bencard SPT allergen
which, while not standardized, provides useful results.
Serum Examinations
RAST (Radioallergosorbent Test). This method uses a blood sample from a
suspected NRL sensitized individual. It measures specific IgE antibodies
against NRL allergens. This method has an 80% sensitivity and 100%
specificity in non-atopic individuals. This method is available from
Pharmacia in Sweden.
ALaSTAT (DPC). Similar in principle to the RAST procedure, this method
has a sensitivity of 80% and a specificity of 100% in non-atopic
individuals. In atopic individuals, especially those allergic to fruits
and vegetables, this test can produce over 30% false positive results.
Use or Challenge Test
This procedure requires the person either to wear a finger of the NRL
glove or a whole NRL glove on one hand while using a PVC glove on the
other hand as a negative control. The person is then examined over a
period of time (15 minutes) to see if any symptoms develop.
The Challenge or Use Test is conducted when the SPT result is not in
concordance with case history. People with slightly positive SPT or RAST
or AlaSTAT results, as well as people who are thought to be allergic to
gloves but the tests remain negative, should always be given the Use
Test to verify if the slight reactions are real, .
People with a history of anaphylaxis should not be subjected to the Use
Test as there is a risk that a generalized reaction such as anaphylaxis
can occur. For the same reason, the Use Test can be done only in an
office with adequate equipment to treat anaphylaxis.
