It is very difficult to give a reliable estimate of the true prevalence of soy allergy in the general population.

The true prevalence could be even higher since liver enzyme profiles were not done in all patients.

"Both were carefully done and highly reputable studies, and the true prevalence is probably somewhere in between these two estimates," says Harris.

So the true prevalence, he said, is probably higher than reported.

This renders the resulting percent change estimates over time utterly uninformative about changes in true prevalence.

Note that the frequency of this condition does not indicate the true prevalence of chimerism.

The true prevalence or incidence of pulmonary dysfunction in childhood cancer survivors is not clear.

Although no one knows the true prevalence of travel phobias, there is indirect evidence that it is fairly common.

The true prevalence of Balanitis xerotica obliterans is controversial and unclear.

The true prevalence of these calcifications is difficult to accurately state as not all patients undergo brain imaging.