Trio Testing

To aid in variant interpretation, the laboratory may use "trio testing." This involves limited analysis of samples from both parents of the patient (proband). Data derived from the parents' samples serve as controls in the variant analysis for the patient. Trio analysis is particularly useful in classification of de novo pathogenic variants (a variant that is discovered for the first time in a family). If an unaffected parent and the proband carry the same rare variant, it is unlikely the variant is the underlying cause of the proband's condition. Parental information, therefore, helps reduce the number of variants the lab must consider in their data analysis. Although trio testing is often desirable, patients without available biological parents are not excluded from exome testing.

Setting expectations about trio testing

Parents may have the misconception that they are also receiving full exome analysis. Generally, this is not the case; the tests are run for the proband's benefit. Unless consented separately, parental exome information is not used for the parent's own health information.

In certain circumstances, genetic information important to the parent's health care may be reported. For instance, a parent who carries the same variant as their child may be discovered to be mildly affected.

Additionally, parents may have the option of learning if they carry pathogenic variants for unrelated but medically actionable conditions (secondary findings). The ordering provider should check with the lab about what kind of parental results may be disclosed; such policies often vary between labs.