Is There a Blood Test for Latex Allergy?
Latex is a substance obtained from the sap of the Hevea tree brasiliensis. In its production process is added different substances depending on the desired final characteristics.
Diagnosis of Latex Allergy
The clinical history guided by the specialist provides very useful information. The presence of other allergies, atopy, surgeries and risk groups, possible sources of exposure, episodes of urticaria and anaphylaxis are collected, as well as possible reactions in relation to the consumption of plantain, kiwi, avocado and chestnut.
The complementary diagnosis is based in skin tests (prick or intraepidermal test) and determination of specific IgE (blood test).
Is there a Blood Test for Latex Allergy?
What blood tests or laboratory tests are usually done to study the allergy? - In an allergic reaction, different cells (lymphocytes, mast cells, basophils, eosinophils...) and multiple molecules participate, some of them specific to the allergen that triggers the reaction (antibodies or immunoglobulins) and other substances that mediate the allergic response, common for the different allergens (histamine, tryptase, etc). The laboratory techniques available for the diagnosis of allergy are to analyze the specific response, trying to identify the responsible allergen for the patient's symptoms; and, on the other hand to determine the immunological mechanism of the allergic reaction.
Depending on the fraction of blood in which these tests are performed, techniques can be classified into two: serological and cellular techniques.
The serological techniques are performed in the patient's serum, that is, in the blood fraction that remains once the cells and some proteins that are involved in coagulation are removed. This fraction contains the immunoglobulins or antibodies, and other substances called mediators of the allergic reaction, such as histamine or tryptase, among others.
On the other hand, the cellular techniques applied to the diagnosis of allergy are carried out using the in vitro study as the substrate, the effector cells of the allergic reaction isolated from the peripheral blood of the patient, lymphocytes and/or basophils; and observing its activation after in vitro stimulation (in a test tube) with the suspected allergen.
Provocation Test: They are indicated when the story is suggestive and the complementary tests are negative or contradictory, or to rule out latex allergy in patients who do not have symptoms.
The most used is the glove use test, in which a glove finger is first contacted and then a full glove, using a vinyl or nitrile glove as a negative control on the other hand; it is considered positive if the patient presents erythema, pruritus, blisters or respiratory symptoms.
It can also be performed the provocation test bronchial specific by aerosolizing particles of latex either from an aqueous extract or by agitation of powdered gloves, although in children its use is very restricted.
Is it Essential to perform Blood Tests once the Skin Tests are done?
While it is true that skin tests are cheap and easy to perform, blood tests in allergology provide additional information that complements the diagnosis in vivo in most cases. In fact, the determination of specific IgE has a greater specificity than skin tests, in such a way that with the cutaneous tests it is possible to select a large number of patients, among which the true allergic ones would be included, but also some of them that are not really (false positives), and that with the determination of the IgE they are identified in a high percentage. In this way, the combination of both tests increases diagnostic performance.
In addition, while skin tests are not quantitative, the determination of specific IgE actually is. It is important to note that a larger size of the wheal obtained in the skin test is not always related to a higher level of specific IgE.
Later allergy is not common and its diagnosis is sometimes a challenge. Skin tests are complemented by blood tests, although on those occasions when they are not indicated - either by taking drugs that interferes with them or by the presence of skin problems-, blood tests will be the only type of diagnosis available to the doctor.