Latex Allergy Diagnosis and Management

Natural rubber latex is a ubiquitous component of modern life. It consists of proteins from the sap of the Hevea brasiliensis tree. Anaphylaxis to latex is one of the most feared and frequent anaphylactic reactions during surgery and medical procedures, and the number of reactions are increasing. In the year 2000, reactions to latex accounted for 16.6 % of anaphylactic reactions during surgery.

The populations who are at risk for anaphylaxis to latex are as follows:

• Individuals with a genetic predisposition (atopic individuals)

• Individuals with increased previous exposure to latex (e.g., anyone who requires chronic bladder care with repeated insertion of a latex catheter or chronic indwelling catheters, children with spina bifida and meningomyelocele)

• Healthcare workers who are exposed to latex mainly by inhalation

In some cases, patients who have undergone multiple surgical procedures

The incidence of latex sensitivity in the general population ranges from 0.8% to 6.5%. The two main risk groups for latex allergy are physicians and nurses, with an incidence of 7% to 18%. The highest incidence ofla-tex sensitivity has been reported for patients who require chronic bladder care, e.g., children with bladder exstrophy, spina bifida, or meningomyelocele, who have a risk as high as 72 % (Ricci et al. 1999; Taylor and Erkek 2004; Chiu and Kelly 2005).

There are two types of allergic reactions: The delayed hypersensitivity (type IV), which is seen usually in form of a dermatitis reaction. It is a cell-mediated reaction which develops 24-48 h after exposure and can be diagnosed by patch testing. Immediate hypersensitivity (type I) is the more dangerous type of allergy, and its incidence has been rapidly increasing over the last two decades. It represents a latex protein-specific IgE-mediated hypersensitivity with a clinical manifestation ranging from contact urticaria to fatal anaphylactic shock (Taylor and Erkek 2004). Exposure to latex antigen can occur by cutaneous (latex gloves), respiratory (opening latex gloves in the operating room), mucosal (gynecological examination with latex gloves), and parenteral routes (i.v. medication with latex-containing infusion sets), with the latter two having the highest risk of anaphylaxis.

There are allergic cross-reactions in patients with fruit or food sensitivities to avocado, banana, chestnut, potato, tomato, passion fruit, and kiwi (Taylor and Erkek 2004). Therefore, a preexisting fruit allergy may be an additional risk factor for clinically relevant latex allergies.

A diagnostic evaluation is recommended for high-risk patients (e.g., children with urological malformations), and for anyone with a history of urticaria or an-gioedema of the lips when inflating balloons or with itching or contact urticaria when donning gloves, a latex allergy should be suspected. This evaluation should become more comprehensive as needed.

Latex-specific IgE antibodies in serum can be demonstrated in vitro and quantified with RAST or ELISA. Currently, there are three FDA-approved in vitro sero-logic assays for the diagnosis of latex allergy available on the market (ImmunoCAP, Pharmacia-Upjohn, Sweden; AlaSTAT FEIA, Diagnostic Products Corp., Los Angeles, CA, USA; HYTEC EIA, Hycor Biomedical Inc., Garden Grove, CA, USA). All of them have a relatively high rate of false-negative results. Further disadvantages are the costs, delayed results, low sensitivity, and accessibility compared to in vivo tests. However, serol-ogy should be the initial diagnostic step for suspected latex allergy because it is safer than in vivo tests.

The skin prick test is the gold standard. It is easy to perform and provides immediate results (5-30 min). Sensitivity is highly influenced by the quality of the latex extract used, but can be as high as 87%. Additionally, at 66 % the specificity of the skin prick test is higher than the in vitro tests (RAST, ELISA). There is a standardized commercial skin prick test kit available in Europe (Stallergenes SA, Antony, France), but so far no FDA-approved test is available.

The skin prick test as an in vivo test is comparable to a small-scale provocation test. Therefore it should be performed by experienced staff and with oxygen, epi-nephrine, and latex-free resuscitation equipment at hand. Because of rare anaphylactic reactions to the prick test, the in vitro diagnostic work-up should be performed prior to the prick test.

Another possibility is a provocation test by wearing a latex glove. This maybe employed when there is a discrepancy between prick test or specific IgE results and clinical history. It begins as a one-finger test, and extended to a whole-hand test if there is no urticarial reaction after 20 min. Nonlatex vinyl gloves are used as a control. The testing staff has to be aware of the possibility of sudden anaphylactic reactions.

Corticoids and H1 and H2 antagonists can be used to pretreat patients with known latex allergy prior to medical procedures. However, pretreatment is not very effective in preventing reactions to latex, unlike prevention measures for reactions to contrast media. Therefore, the most important factor is avoiding exposure to the allergen. This means taking a thorough patient history, testing for latex allergy in high-risk patients, preadmission measures, and establishing a latex-free environment while the patient is hospitalized, particularly in the operating and recovery rooms (Lieberman 2002). The charts of latex allergic patients should be labeled, and surgery should be scheduled as the first case of the day to reduce exposure to the aerosolized latex allergens. Latex-free equipment should be stored separately: nonlatex gloves, glass syringes, nonlatex tape, synthetic catheters and tubes, latex-free blood pressure cuffs, and three-way stopcocks for i.v. administration of medication.

Allergic reactions to latex are treated in a manner that is analog to all other anaphylactic reactions (compare treatment recommendations in Tables 4.4,4.5, and 4.8).

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