On the testing load incurred by cascade genetic carrier screening for Mendelian disorders: a brief report.

One criterion to decide to whom molecular genetic carrier testing should be provided is an individual's carrier risk, taking into account his or her affection status and degree of relatedness to an overt carrier. We have derived formulas to calculate the testing load incurred to a public health system following such a cascade screening strategy. While the testing load turns out to be moderate for individual diseases at meaningful risk thresholds (i.e., 1%-5%), a substantial proportion of the population would have to be tested if all known single gene disorders were to be included in a cascade screening program.