Informed consent affects prevalence estimates in an epidemiological study on chronic pruritus: lessons learned from a pretest.

PURPOSE

It was the purpose of this study to compare prevalence estimates of chronic pruritus as obtained from two population-based samples, one being asked and one not being asked to provide written informed consent.

METHODS

A validated questionnaire measuring the prevalence of chronic itch was sent to two samples (N=51 and N=52) from the general population; one sample was asked to complete and send back an informed consent form and one sample was not.

RESULTS

There were few demographic differences between the two groups. The response rate was slightly higher in those who were not asked to complete an informed consent form. Point, 12-month, and lifetime prevalence estimates in those persons who had not received a consent form, but who had written back were consistently lower (lifetime prevalence: 16% vs. 60%, p=0.01).

CONCLUSIONS

If informed consent is requested, there seems to be a relationship between the presence of chronic pruritus and the willingness to participate in a cohort study. People suffering from chronic pruritus tend to return the questionnaire with the informed consent form more readily. Measures need to be taken to ensure that the response is sufficiently high among participants without the target characteristic in epidemiological studies on chronic symptoms.