Example natural rubber and latex allergy

Reactions to latex in medical devices can be used to illustrate many of the general considerations. Latex is a component in a wide variety of medical [including medical and surgical gloves (see Figure 19.2), condoms, diaphragms, cervical caps, barium enema cuffs, dental dams, airway tubes, anesthesia masks, tympanostomy tubes, douche bulbs, elastic bandages, ostomy bags, manual ventilation bags] and consumer products (including rubber bands, cleaning gloves, balloons, elastic, baby bottle and pacifier nipples, carpet backing, erasers, eye dropper bulbs, hot water bottles, balls, toys, hand grips on equipment). Dry rubber is generally made in a different way from latex and is used for other consumer, automotive, and household products, such as tires and shoe soles [39].

Natural latex is a complex material. It is currently recovered from rubber trees (most are on rubber tree plantations in Malaysia) by tapping the bark to extract the milky-looking sap (latex) and removing some of the clear serum by centrifugation. The concentrated latex is then treated with ammonia, chlorine, or other chemicals, depending on the desired product. The shape of the final product is created by techniques such as dipping (hand-shaped blocks are dipped in the liquid and pulled back out to create gloves), foaming to form a sponge, or extrusion into thread or elastic. To stabilize the object, it is rinsed and then vulcanized (cured) in ovens. After the vulcanization, the products are rinsed again to leach allergenic proteins. The original sap is a mix that includes various carbohydrates and proteins [39], which vary by the immediate environment of the trees and tree genetics [40].

Natural rubber usage changed in the late 1980s, when it was recognized as a barrier to the transmission of the virus that causes acquired immune deficiency syndrome (AIDS). Until then, gloves had been used for sterility and protection from known infections; after the call for the use of universal precautions to protect all patients and workers as if all of them were infectious, glove use for all medical and some non-medical situations rose sharply [41,42]. The rubber industry changed its production processes, presumably by making them faster, as part of its effort to meet demand [42].

In the 1980s, several case reports of latex allergy among patients and healthcare workers were published [42]. In 1990, the Center for Devices and Radiological Health (CDRH) in the Food and Drug Administration (FDA) received reports of two instances of severe anaphylaxis. Each patient had seemed robust and then suddenly went into anaphylactic shock and died as they were being prepared for barium enemas for imaging their colons. FDA already had many reports on file of allergic reactions associated with barium, but these were the first where the barium solution had not yet been given. The exposures considered as potentially causing these severe reactions were the lubricating jelly and the barium enema cuffs, which were made of latex. Given the sensitivity of rectal mucosal tissues, the recent reports of latex allergy, and the lack of any particular reasons to suspect the lubricating jelly, the barium enema cuffs were implicated [43].

Laboratory studies have shown that the processing of natural rubber results in a mesh that physically, rather than chemically, traps the various (up to 60) allergenic proteins [40,44-46]. Rinsing during production eliminates most of the overall protein, and rinsing after production removes the remaining proteins on the surface [39]. After production, the proteins continue to migrate to the surface of the product, but less rinsing during production results in more surface proteins later [39]. Although the demand for barium enema cuffs had not particularly increased in the late 1980s, all medical latex production had increased and the production quality for barium enema tips might have decreased, resulting in more surface proteins on the surface of the tips. The surface proteins can be carried to skin by direct contact or, more effectively, by a liquid, such as perspiration [47]; they can also be carried into the lungs on particles of powder that become airborne, such as during glove donning [48-50]. The rubber industry has reacted to this recent understanding of the causes of latex allergy by developing and using processing protocols that reduce the amount of protein in their products [39].

Almost any type of tissue can be exposed. Tissue reactions can be more severe for mucous membrane, lung, and wound exposure, and are generally allergic in nature. The allergic reactions are driven by immunoglobulins and the predominant immunoglobulin type varies in different tissues. An individual's allergic reaction to latex depends on route of exposure, history of exposure, quantity of exposure, and genetic susceptibility.

Designers of epidemiologic studies have to consider definitions of exposure, outcome, and the population to be studied. Almost everyone has at least some exposure to latex, since consumer products are common and almost universally used. Therefore, in assessing latex exposure in epidemiologic studies, one needs to consider the magnitude, duration, and route of exposure, as well as the sensitivity of the exposed tissues. This strategy has led to the frequent choice of healthcare workers, who are often exposed on their skin and airways for long periods of time, and patients with frequent surgeries, who are exposed via their airways and surgical incisions, for 'exposed' cohorts (see Tables 19.3 and 19.4 for more specifics). Other strategies have been to examine the relative allergenicity of types of latex gloves by comparing, among healthcare workers, use of powdered vs. nonpowdered gloves [51,52], or use of gloves with and without large amounts of surface proteins [52,53], or use of gloves made by different manufacturing processes [39].

Measurement of latex allergy (the outcome in this example) is complicatedby the need to consider delayed vs. immediate reaction, the severity of reaction, and whether one will rely on clinical history or some type of 'objective' test. Skin prick tests rely on a solution of latex allergens, which may or may not include the particular protein to which the subject is allergic, because of the large number of candidate allergens. The major problem with skin prick tests is that they place the subject at risk of a severe anaphylactic reaction. Another test, which does not place the subject at risk, is the radioallergosorbent test (RAST), where blood is drawn and tested for the presence of reactive immunoglobulins [41]. Like the skin prick test, the RAST test also may fail to test for the exact protein to which the subject is allergic. Two brand name antigen supplies that have been used in published studies include AlaSTAT [54-59] and CAP [60,61]. The lack of accuracy of these methods of measuring latex allergy has been reflected in discordance between the results of any two or all three of the allergy measurement methods used on individuals [62,63]. Discordant results have been documented between self-reports and skin tests [60,64-68], between self-reports and blood tests [58,60,67], and between skin tests and blood tests [60,68]. There have also been discrepancies in skin tests that were performed with different extracts [68] and between blood tests done with different assays [56].

Large numbers of study subjects are desirable because rates of latex allergy tend to be low and the outcome measures are not precise. Since willingness to participate may be correlated with latex sensitivity, high participation rates are important. Unfortunately, high participation rates are difficult to achieve when subjects are asked to undergo risky, uncomfortable, or invasive tests.

In attempting to determine the prevalence of latex sensitization in the general population, large study sizes and reasonably high participation rates (see Table 19.3) were obtained in studies of students who were beginning an apprenticeship, blood donors,

Table 19.3 Prevalence of latex allergy reported in the literature for people who are not occupationally exposed to latex, arranged by population, measure of latex allergy, finding, study size, and participation rate

Estimated

Study

Participation

Latex allergy

prevalence

size

rate (%)

Population

measure

(%)

(n)

Reference

General population

Students before

Skin test

0.70

769

100

Gautrin

starting

et al. [71]

apprenticeship

Blood donors

Blood donors in

Latex-specific

4

2000

100

Merrett

midwinter

IgE, by AlaSTAT

et al. [55]

Blood donors at a

Latex-specific

6.4

1000

100

Ownby

non-hospital

IgE, by

et al. [56]

worksite

AlaSTAT

Blood donors in

Latex-specific

7

5000

100

Merrett

midsummer

IgE, by AlaSTAT

et al. [55]

Patients

Emergency room

Latex sensitivity,

1.6

1027

89

Grzybowski

patients

by questionnaire

et al. [58]

Adult surgery

Rubber intolerance,

5.8

325

75

Rueff

patients

by questionnaire

et al. [72]

Surgery patients

Skin prick test

0.8

1000

100

Sanchez-

with history

Fernandez

of drug allergy

et al. [81]

or atopy

Adult surgery

Skin prick test

4.9

285

66

Rueff et al.,

patients

2001 [72]

Adult surgery

Latex-specific IgE

7.1

323

75

Rueff

patients

et al. [72]

Ambulatory surgery

Latex-specific IgE,

7

996

100

Lebenbom-

patients

by AlaSTAT

Mansour et al. [57]

Emergency room

Latex-specific IgE,

8.2

1027

89

Grzybowski

patients

by AlaSTAT

et al. [58]

Patients being

Latex-specific IgE,

12

200

Not

Reinheimer

evaluated

by AlaSTAT

reported

et al. [59]

for any type of allergy for any type of allergy surgical patients, emergency room patients, and patients being evaluated for any type of allergy. The blood donors and patients may have experienced higher latex exposures than the general population, because highly exposed patients, such as those with spina bifida, have been shown to have especially high latex allergy rates (24-60%) [69]. The different

Table 19.4 Prevalence of latex allergy reported in the literature for people who are traditionally occupationally exposed to latex, arranged by population, measure of latex allergy, finding, study size, and participation rate

Estimated

Latex allergy prevalence Study Participation

Population measure (%) size (n) rate (%) Reference

Documented or presumed frequent latex exposure

Medical, surgical,

Symptoms, by

17.2

1165

95

Larese Filon

and laboratory

questionnaire

et al. [73]

staff

Operating room

Symptoms, by

41

248

93

Lagier et al.

nurses

questionnaire

[64]

Hospital staff

Latex allergy, by questionnaire

40

504

55

Kaczmarek et al. [41]

Hospital staff

Symptoms, by questionnaire

7

1827

Not reported

Sinha et al. [74]

Operating room

Symptoms, by

55

247

Not

Mace et al.

nurses

questionnaire

reported

[66]

Anesthesiologists

Contact dermatitis,

20

168

98

Brown et al.

and nurse

by questionnaire

[60]

anesthetists

Medical, surgical,

Contact urticaria,

3

1165

95

Larese Filon

and laboratory

by questionnaire

et al. [73]

staff

Dental school staff

Glove-related dermatitis, by questionnaire

22

177

77

Katelaris et al. [75]

Dental school staff

Prompt glove-related urticaria, by questionnaire

9

177

77

Katelaris et al. [75]

Dental school staff

Glove-related non-hand symptoms, by questionnaire

33

177

77

Katelaris et al. [75]

Hospital staff

Non-cutaneous symptoms, by questionnaire

8.1

1294

50

Nettis et al. [68]

Anesthesiologists and

Type I latex

2

168

98

Brown et al.

nurse anesthetists

allergy, by questionnaire

[60]

Hospital operating

Type I latex allergy

18

314

49

Smedley et

room staff

symptoms, by questionnaire

al. [54]

Hospital infectious

Type I latex

12

58

43

Smedley et

disease and

allergy

al. [54]

outpatient nurses

symptoms, by questionnaire

Hospital nurses,

Glove-related

4.7

273

94

Vandenplas

cleaning staff,

urticaria, by

et al. [65]

and technologists

questionnaire

(Continued)

Table 19.4 (Continued)

Estimated

Latex allergy

prevalence

Study

Participation

Population

measure

(%)

size (n)

rate (%)

Reference

Hospital nurses,

Skin prick test

4.7

273

94

Vandenplas

cleaning staff,

et al. [65]

and technologists

Anesthesiologists and

Skin prick test

11

154

90

Brown et al.

nurse anesthetists

[60]

Operating room

Skin prick test

11

197

74

Lagier et al.

nurses

[64]

Hospital staff

Skin prick test

12

1351

66

Liss et al. [76]

Operating room staff

Skin prick test

2

202

Not

Wrangsjo

and dental staff

reported

et al. [61]

Hospital staff

Skin prick test

2.9

512

Not reported

Turjanmaa [77]

Operating room

Skin prick test

5.6

Not

Not

Turjanmaa

nurses

reported

reported

[77]

Operating room

Skin prick test

7.4

Not

Not

Turjanmaa

physicians

reported

reported

[77]

Hospital anesth-

Skin prick test

9.9

101

Not

Arellano

esiologists,

reported

et al. [78]

radiologists,

and surgeons

Hospital nurses

Skin prick test

13.3

Not

Not

Liss et al.

and physicians

reported

reported

[76]

Hospital laboratory

Skin prick test

17

Not

Not

Liss et al.

staff

reported

reported

[76]

Hospital staff

Skin prick test

17

224

Not reported

Yassin et al. [79]

Anesthesiologists and

Latex-specific

8

168

98

Brown et al.

nurse anesthetists

IgE, by CAP

[60]

Hospital nurses

Latex-specific IgE

8.9

741

90.6

Grzybowski et al. [58]

Operating room and

Latex-specific

2

193

Not

Wrangsjo

dental staff

IgE, by RAST with CAP

reported

et al. [61]

Nurses

Latex-specific IgE, by RAST

3

226

Not reported

Waclawski [80]

Documented reduced

or minimal latex

exposure

Hospital staff

Symptoms, by questionnaire

0

227

Not reported

Sussman et al. [51]

Dental students

Glove-related rhinoconjunc-tivitis, by questionnaire

0

57

36

Saary et al. [52]

Dental students

Glove-related urticaria, by questionnaire

4

57

(Continued)

Table 19.4 (continued)

Estimated

Latex allergy

prevalence

Study

Participation

Population

measure

(%)

size (n)

rate (%)

Reference

Dental school staff

Glove-related urticaria, by questionnaire

11

36

Not reported

Saary et al. [52]

Dental school staff

Glove-related rhinoconjunc-tivitis, by questionnaire

19

36

Not reported

Saary et al. [52]

Hospital staff

Skin prick test

1

227

Not reported

Sussman et al. [51]

Hospital staff

Skin prick test

12

1351

66

Liss et al. [76]

Dental students

Skin prick test

0

57

36

Saary et al. [52]

Dental school staff

Skin prick test

8

36

Not reported

Saary et al. [52]

studies used different methods to assess latex allergy, such as questionnaires, skin prick tests, andblood tests. The estimates of latex allergy prevalence varied (0.7-12%), with no obvious pattern in the type of people most likely to be sensitive, type of measure, participation rate, or year of study.

Table 19.4 summarizes studies of the prevalence of latex sensitization among healthcare workers who are traditionally occupationally exposed to latex. The study sizes and participation rates were highly variable. For the study populations with documented or presumed frequent latex exposure, the questionnaire method resulted in prevalence estimates in the range 3-55%, the skin prick test 2-17%, and the blood test 2-8.9%. For studies of healthcare workers where latex exposure had been systematically and dramatically reduced, the questionnaire method resulted in prevalence estimates of 0-19% and the skin prick test 0-12%. The prevalence rates from the studies of healthcare workers also do not show a clear relationship with type of healthcare worker, latex allergy measure, study size, participation rate, or year of study. One problem with interpreting latex allergy prevalence rates among healthcare workers is that those who are least willing to tolerate latex exposure are most likely to discontinue direct healthcare work, resulting in a presumed underestimate of the impact of latex exposure.

A better measure of the burden of latex allergy on healthcare workers is the incidence (rate of new onset) of latex sensitization onset. Data from the Finnish Register of Occupational Diseases showed that the reported incidence rates of latex contact urticaria were 0.2/10 000 per year for the overall working population, 2.2/10 000 per year for working nurses, 3.9/10 000 per year for working physicians, 6.0/10 000 per year for working dentists, and 11.8/10 000 per year for working dental assistants [70]. A study of 122 apprentices in dental hygiene technology throughout their training showed much higher incidence rates of self-reported measures: 249/10 000 per year for skin sensitization, 177/10 000 per year for asthma, and 35/10 000 per year for rhinoconjunc-tivitis [9]; this rate may have been much higher because it was self-reported rather than verified in some way. A study of the incidence of latex allergy onset among Mayo Clinic employees who regularly use gloves showed that it was very low (2.5/10 000 per year) through 1987, then rose to a peak of 27/10 000 per year for 1990-1993; after high-allergen gloves were removed from the work areas in early 1994, the incidence in 1994 fell to 12/10 000 per year and thereafter to 0 to 2/10 000 per year [53].

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