Comparison of three immunoassays for diagnosing sensitization to latex in children with spina bifida

Strategies for distinguishing asymptomatic latex sensitization from true occupational allergy or asthma

OBJECTIVE

To evaluate strategies for distinguishing those individuals with true occupational asthma caused by exposure to natural rubber latex from those individuals with allergic disease related to other allergens.

DATA SOURCES

Article published between January 1, 1981, and December 31, 2001, were identified via a MEDLINE search with the following keywords: latex, allergy, asthma, occupation asthma, and adverse reactions.

STUDY SELECTION

English-language reports concerning diagnostic methods in latex and other forms of occupational asthma.

RESULTS

Many methods have been evaluated for the diagnosis of latex allergy, including medical history, skin prick tests, in vitro tests, and various challenge tests. Skin prick tests with well characterized latex extracts are highly sensitive and specific predictors of latex-specific IgE antibodies; however, direct pulmonary challenge with latex allergen appears to be the only highly reliable method for diagnosis of latex-related occupational asthma.

CONCLUSIONS

It is difficult to optimally distinguish between occupational latex asthma and asymptomatic latex sensitization in a person with preexisting asthma using currently available techniques.

Is there a role for immunoblots in the diagnosis of latex allergy? Intermethod comparison of in vitro and in vivo IgE assays in spina bifida patients

BACKGROUND

The best diagnostic method for latex allergy is still controversial. This investigation was designed to evaluate the diagnostic efficiency of immunoblotting in comparison with established in vitro and in vivo test systems.

METHODS

A total of 108 spina bifida patients were investigated by questionnaire and skin prick test (SPT). Specific serum IgE to latex was analyzed by the Pharmacia CAP FEIA immunoassay, DPC AlaSTAT microplate immunoassay, and DPC AlaBLOT immunoblot. Patients were regarded as latex allergic if they reacted positively to challenge by the latex glove wearing test.

RESULTS

Thirty-four patients reacted positively to challenge. The sensitivity rates were 97% (SPT), 94% (immunoblot, CAP), 74% (AlaSTAT), and 35% (clinical history). The specificity rates were 92% (clinical history), 88% (AlaSTAT), 77% (SPT), 76% (CAP), and 69% (immunoblot). If two methods were combined, efficiency rates were highest for SPT combined with CAP (sensitivity 94%, specificity 82%), with AlaSTAT (sensitivity 74%, specificity 92%), or with immunoblot (sensitivity 91%, specificity 84%). The sera of challenge-positive patients recognized more immunoblot bands than challenge-negative patients, and the severity of symptoms correlated with the number of recognized bands. CONCLUSIONS The diagnostic efficiency of immunoblotting is not superior to that of SPT. However, immunoblotting may serve as an additional tool to increase slightly the specificity of SPT and specific serum IgE tests.

The search of latex sensitization in spina bifida: diagnostic approach

BACKGROUND

Sensitization to latex has become a major problem in children with spina bifida. Life-threatening reactions may occur in these patients, therefore the search of latex sensitization must be an active task in all of these children.

OBJECTIVE

To design an approach for the diagnosis of latex sensitization in children with spina bifida.

METHODS

We studied 100 consecutive unselected patients. Skin prick tests with a commercial latex extract were performed, latex-specific serum immunoglobulin (Ig) E was determined by CAP test, and risk factors were studied. Originally, patients with an area of latex skin test > 50% of the area of histamine and/or CAP class > or = 3 were considered sensitized to latex. Diagnostic tests were also performed in a control group of 51 atopic and nonatopic children.

RESULTS

After performing a receiver-operating characteristics curve for both tests we recommend skin tests > 25% of the area of histamine (sensitivity - SEN = 79%, specificity - SPE = 100%, positive predictive value - PPV = 100%, negative predictive value - NPV = 90%), or CAP class > or = 2 (SEN = 88%, SPE = 100%, PPV = 100%, NPV = 94%) as diagnostic cut-off points. The anamnesis had a SEN of 44% for diagnosis, and a SPE of 100%. Latex sensitization was associated with more than 5 operations (OR = 8, 95% CI = 3-21.3), a personal history of atopy (OR = 11.5, 95% CI = 2.3-57.1), and serum total IgE > or = 2 z-units (OR = 4, 95% CI = 1. 6-10).

CONCLUSION

For the routine evaluation of children with spina bifida, we propose a diagnostic algorithm with skin prick tests as a first step and CAP second.

A new dipstick test (Allergodip) for in vitro diagnosis of latex allergy--validation in patients with spina bifida

While there is established data on the value of various assays for determining specific immunoglobulin E (IgE) in serum, little has been reported about semi-quantitative dipstick methods. Therefore, in a pilot study we compared a new dipstick assay (Allergodip) with a well-evaluated commercial assay (Pharmacia CAP-system), in terms of sensitivity and specificity, in sensitized and nonsensitized, symptomatic and non-symptomatic patients with spina bifida. One-hundred and thirty-five patients with spina bifida (median age 10.8 years) were included in this study. Sixty-nine patients (51.1%) were positive in the CAP-system, 61 patients (45.2%) were positive in the Allergodip assay, and 67 patients (49.6%) were positive in a skin prick test with natural rubber latex milk. The concordance between the CAP-system and Allergodip was good. Forty-seven patients (34.8%) showed a positive response to the provocation test. The sensitivity of Allergodip was 85.1% compared with 91.5% for the CAP-system. Specificity was 75.0% for the Allergodip assay and 70.5% for the CAP-system. We conclude that the new dipstick test is a useful screening test for diagnosing sensitization to latex, e.g. when planning surgical interventions. However, in instances of doubtful reactions, discrepancies with clinical features or for scientific work it does not replace quantitative determination of specific IgE.

Latex allergy in an Australian population of children and adolescents with spinal dysfunction

OBJECTIVES

To determine the prevalence of latex allergy in an Australian population of children and adolescents with spinal cord dysfunction and a comparison population of their siblings without spinal dysfunction.

DESIGN AND SETTING

Cross-sectional study of all patients with spinal cord dysfunction attending the single tertiary spinal dysfunction clinic in Western Australia, and of their siblings closest in age.

SUBJECTS

104 patients with spinal dysfunction born 1978-1996 inclusive, and 50 siblings.

MAIN OUTCOME MEASURES

Prevalence estimates and adjusted odds ratio estimates of the risk of having a history of latex allergy and of testing latex-specific IgE positive.

RESULTS

Of the patients, 15.4% (95% CI, 9.1%-23.8%) had a history of latex allergy compared with none (95% CI, 0-5.8%) of the siblings. Of the 84 patients tested, 36.9% (95% CI, 26.6%-48.1%) were latex-specific IgE positive compared with 15.4% (95% CI, 4.4%-35.9%) of the 26 siblings tested. For patients, every operation after the first increased the risk of a positive IgE result cumulatively by 41% (odds ratio, 1.41; 95% CI, 1.18-1.68).

CONCLUSIONS

The prevalence of latex sensitivity and clinical allergy in children and adolescents with spinal dysfunction in Australia is as high as that seen in the United States, and is related to latex exposure during surgery. The management policy regarding latex exposure for patients with spinal dysfunction requires urgent consideration.