Validity of the IUATLD (1986) questionnaire in the EGEA study

SETTING: No validity study of the IUATLD asthma-like questions has been performed in a group of well-defined, clinically-based asthmatics.

OBJECTIVES: To assess the validity of the questions regarding asthmatics included in a case-control study, and to assess their validity as regards bronchial hyperresponsiveness in population-based subjects.

DESIGN: Data from the case-control Epidemiological study on the Genetics and Environment of Asthma, bronchial hyperresponsiveness and atopy (EGEA) were used. The analysis concerned 201 adult asthmatic cases recruited in chest clinics through a standardised protocol and 284 population-based controls.

RESULTS: The analysis of the case-control study regarding asthma showed a sensitivity of 0.56, 0.68 and 0.86 for nocturnal symptoms of cough, shortness of breath, and chest tightness, and a specificity of 0.72, 0.98 and 0.89. As regards bronchial hyperresponsiveness (PD₂₀ ≤4 mg) in the control group, specificity was high (0.77, 0.99 and 0.90), but sensitivity was markedly lower (0.36, 0.11 and 0.20).

CONCLUSION: Asthma-like symptoms assessed by the IUATLD questionnaire have good validity, both for specificity and sensitivity, for asthma patients recruited in chest clinics. In general populations, questions have a high specificity, an important criterion in aetiological epidemiological research, and they were designed in that perspective. However their moderate sensitivity limits their usefulness as a screening test.