controls, intradermal testing can be used to demonstrate low levels of sensitization when allergy is clinically suspected. However, studies are necessary to determine the optimal concentrations and methods for skin testing and to address the relationship between defined skin test reactions and disease.

With respect to the specificity and sensitivity of skin tests within a population, more research is needed to determine the predictive values of both prick and intradermal tests. Moreover, the doses and criteria for positive skin tests used for such studies need further definition, together with criteria to define the relationship of a positive skin prick test to the wheal area or erythema that appears.

Recommendation: Encourage the development and use of improved standardized methods for performing and interpreting skin tests.

Pulmonary Function Tests

There are simple, reliable measures of lung function that may be used for studying diseases caused by indoor allergens. Indeed, objective measures of respiratory function should be a part of protocols to determine the efficacy of therapeutic strategies for these diseases. Predicted values for pulmonary function fall along a normal distribution curve with 95 percent confidence intervals for FEV1 and FVC of approximately 80–120 percent. The lower limit of variation in population studies for the midlevel expiratory flow rate (FEF25–75) is approximately 60 percent.

Spirometry is limited in its ability to detect impairment of ventilatory function in asymptomatic individuals because of the wide range of normal values, even with predicted levels that control for age, sex, and height. Significant inaccuracy can result from errors in spirometry performance, almost all of which lead to underestimation of the true respiratory function. These tests can, however, help to evaluate the effects on an individual of sensitization to specific allergens. They can also help to diagnose respiratory diseases that may be caused or worsened by indoor allergens and to assess disease severity, which is often critically important in clinical decisionmaking. Serial pulmonary function testing in the home or workplace can demonstrate causal relationships between the indoor environment and respiratory illness. Serial pulmonary function testing coupled with bronchoprovocation can demonstrate the causal relationship between specific allergens and respiratory responses.

In epidemiological studies, measures of environmental factors and of pulmonary function can be evaluated for associations that suggest causal relationships. Pulmonary function tests may also be used to assess the efficacy of therapy, determine response to treatment, or determine the effect of environmental modification. Such tests are required when physicians are

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