Diagnostic model for sensitization in workers exposed to occupational high molecular weight allergens

Medical surveillance for prevention of occupational asthma

PURPOSE OF REVIEW

Because there is sufficient knowledge of its environmental determinants, occupational asthma is a disease that ought to be largely preventable; yet its incidence in many settings remains unacceptably high. Here we review one approach to prevention: the routine use of health surveillance in exposed workforces.

RECENT FINDINGS

Health surveillance is widely practised but there is little evidence that it is used strategically to reduce disease incidence. There are several barriers to the effective use of its various components, chiefly symptoms questionnaires and spirometry. Cost-benefit analyses may help to increase the uptake of industry-wide workplace interventions.

SUMMARY

The effective use of health surveillance for occupational asthma continues to be challenging and there remains relatively little published evidence that will encourage those involved to use it more efficiently. Useful advances could be made by greater collaboration between employers, employee organizations, legislators and researchers.

Exposure to flour dust and sensitization among bakery employees

BACKGROUND

The National Institute for Occupational Safety and Health conducted a study to determine prevalences of sensitization to bakery-associated antigens (BAAs) and work-related respiratory symptoms at a large commercial bakery.

METHODS

The following measurements were carried out: personal breathing zone (PBZ) and general area (GA) monitoring for inhalable flour dust, α-amylase and wheat, a questionnaire, and blood tests for IgE specific to flour dust, wheat, α-amylase, and common aeroallergens.

RESULTS

Of 186 bakery employees present during our site visit, 161 completed the questionnaire and 96 allowed their blood to be drawn. The geometric mean PBZ and GA inhalable flour dust concentrations for the lower-exposure group was 0.235 mg/m(3), and for the higher-exposure group was 3.01 mg/m(3). Employees in the higher-exposure group had significantly higher prevalences of work-related wheezing, runny nose, stuffy nose, and frequent sneezing than the lower-exposure group. The prevalence of IgE specific to wheat was significantly higher among employees who ever had a job in the higher-exposure group or in production at another bakery at both the ≥ 0.10 kU/L and the ≥ 0.35 kU/L cutoffs, and to flour dust and α-amylase at the ≥ 0.10 kU/L cutoff, compared to the lower-exposure group.

CONCLUSIONS

Despite knowledge of the risks of exposure to flour being available for centuries, U.S. employees are still at risk of sensitization and respiratory symptoms from exposure to high levels of BAA.

A diagnostic model for the detection of sensitization to wheat allergens was developed and validated in bakery workers

OBJECTIVES

To develop and validate a prediction model to detect sensitization to wheat allergens in bakery workers.

STUDY DESIGN AND SETTING

The prediction model was developed in 867 Dutch bakery workers (development set, prevalence of sensitization 13%) and included questionnaire items (candidate predictors). First, principal component analysis was used to reduce the number of candidate predictors. Then, multivariable logistic regression analysis was used to develop the model. Internal validation and extent of optimism was assessed with bootstrapping. External validation was studied in 390 independent Dutch bakery workers (validation set, prevalence of sensitization 20%).

RESULTS

The prediction model contained the predictors nasoconjunctival symptoms, asthma symptoms, shortness of breath and wheeze, work-related upper and lower respiratory symptoms, and traditional bakery. The model showed good discrimination with an area under the receiver operating characteristic (ROC) curve area of 0.76 (and 0.75 after internal validation). Application of the model in the validation set gave a reasonable discrimination (ROC area=0.69) and good calibration after a small adjustment of the model intercept.

CONCLUSION

A simple model with questionnaire items only can be used to stratify bakers according to their risk of sensitization to wheat allergens. Its use may increase the cost-effectiveness of (subsequent) medical surveillance.

Allergic rhinitis in laboratory animal workers and its risk factors

BACKGROUND

The workers in an animal laboratory are exposed to laboratory animal allergens (LAAs).

OBJECTIVES

To evaluate the difference of sensitization to LAAs and the symptoms according to the exposure levels and to investigate the risk factors for sensitization to LAAs.

METHODS

The subjects were divided into 3 groups according to the presence or absence of exposure: 74 subjects were in the direct exposure group, 33 subjects were in the indirect exposure group, and 30 subjects were in the control group. Each group answered the questionnaire and underwent skin prick tests that included 10 common allergens and 10 LAAs. The levels of total IgE and specific IgE to mouse and rat urine allergen were measured by enzyme-linked immunosorbent assay in 2 exposure groups. Allergic symptoms, skin sensitization, and serum IgE level were compared between the study groups.

RESULTS

Twenty-five (34%) of the 74 subjects in the direct exposure group experienced allergic symptoms since their exposure to laboratory animals. The subjects in the direct and indirect exposure groups had more sensitization to LAAs than did the control subjects. The direct exposure group had more positive results for total IgE than did the indirect exposure group. The subjects in the direct exposure group with atopy had more severe allergic symptoms than the subjects in the indirect exposure group with atopy. Atopy and total IgE level were risk factors for the sensitization to LAAs for the direct exposure group (odds ratios, 7.47 and 7.33, respectively).

CONCLUSIONS

Indirect exposure may be as risky for sensitization to LAAs as direct exposure. More careful protection is needed for laboratory animal workers with atopy.

Variability in the diagnosis of occupational asthma and implications for clinical practice

PURPOSE OF REVIEW

The purpose of this review is to provide a summary of recent evidence relating to occupational asthma diagnosis.

RECENT FINDINGS

Recent evidence suggests that whilst prolonged asthmagen exposure worsens the prognosis, many steps in the diagnostic process are problematic for workers with possible occupational asthma. Certain workers suffer delay prior to specialist assessment, and assessment itself may be of variable quality. Emerging evidence suggests that whilst experts agree about certain aspects of case assessment, there is still likely to be variation in clinical practice. Implications of this variation for the workers assessed are relatively under researched.

SUMMARY

Future research needs to focus not only on improving diagnostic testing, but also on improving consistency and agreement over diagnosis.

The Dutch diagnostic model for laboratory animal allergen sensitization was generalizable in Canadian apprentices

OBJECTIVE

To assess the transportability of an existing diagnostic questionnaire model for the sensitization to laboratory animal (LA) allergens.

STUDY DESIGN AND SETTING

The model was externally validated in 414 Canadian animal health apprentices. Several approaches were used: (1) no adjustment; (2) recalibration of the intercept of the model; (3) re-estimation of the intercept and the regression coefficients of predictors; and (4) model revision, by excluding the existing predictor(s) and/or including new predictor(s). The bootstrapping procedure was done following the third and fourth methods. The calibration was assessed graphically and with the Hosmer-Lemeshow (HL) test. Discriminative properties were determined by the area under the receiver operating characteristic curve (ROC area).

RESULTS

When applied without adjustment, the model's discriminative ability was adequate (ROC area was 0.74 vs. the original ROC area of 0.76); the calibration was poor (HL test P<0.001). The other methods yielded models with good calibration (P>0.10) and reasonable discrimination (ROC area ranged between 0.73 and 0.75). The refitted and revised model showed a good internal validity (correction factor from the bootstrapping procedure was more than 0.90).

CONCLUSION

Once updated, the diagnostic model is valid and can be applied with reasonable performance in an animal health apprentice setting.

New insights into laboratory animal exposures and allergic responses

PURPOSE OF REVIEW

To update the epidemiology of laboratory animal allergy, identify new exposures in the laboratory animal workplace, discuss complexities in the exposure-response relationship, and review the immunology of symptomatic and allergic responses.

RECENT FINDINGS

Laboratory animal allergy remains a common occupational hazard of research scientists, technicians and animal handlers. The epidemiology is typical of a stable workforce: incidence is low, although prevalence is high. Risk factors of atopy, current exposures, and sensitization to cats or dogs incompletely predict disease. Exposures include a complex, potent mixture of allergens, biological adjuvants such as endotoxin and irritants. The dose-response relationship between laboratory animal exposure, sensitization and symptoms is hard to define: cross-sectional studies identify most sensitized workers in moderate laboratory animal exposure, not in the highest exposure. Exposure assessments based on workday averages underestimate exposure peaks that may be significant for symptoms and disease. Although we have assumed that workers without symptoms are not sensitized to laboratory animal allergens, recent data demonstrate that many asymptomatic workers do make laboratory animal-specific immune responses that may be necessary to prevent symptomatic disease.

SUMMARY

Understanding laboratory animal exposures and disease must include exposures other than allergen, and responses other than allergic disease.