preferred_name: A proper value is applicable but not known. (e.g., date of diagnosis is unknown)
preferred_name_lc: a proper value is applicable but not known. (e.g., date of diagnosis is unknown)
label: A proper value is applicable but not known. (e.g., date of diagnosis is unknown)
label_lc: a proper value is applicable but not known. (e.g., date of diagnosis is unknown)