Proband

"Proband", "proposito" (male proband), or "proposita" (female proband) is a term used most often in medical genetics and other medical fields to denote a particular subject (person or animal) being studied or reported on. On pedigrees, the proband is noted with a square (male) or circle (female) shaded accordingly. It is important to denote the proband, so that the relationship to other individuals can be seen and patterns established.

In most cases, the proband is the first affected family member who seeks medical attention for a genetic disorder. Among the ancestors of the proband, there may be other subjects with the manifest disease, but the proband typically refers to the member seeking medical attention or being studied, even if affected ancestors are known. Often affected ancestors are unknown due to the lack of information regarding those individuals or about the disease at the time they lived. Other ancestors might be undiagnosed due to the incomplete penetrance or variable expressivity.

The diagnosis of a proband raises the index of suspicion for the proband's relatives and some of them may be diagnosed with the same disease. Conventionally, when drawing a pedigree chart, instead of the first diagnosed person, the proband may be chosen from among the affected ancestors (parents, grandparents) from the first generation where the disease is found.

The term proband is also used in genealogy, where it denotes the root node of an ahnentafel, also referred to as the progenitor.