“…Rarely (less than 5%) HOA cases have been associated with a normal p50 value, especially if there are comorbidities present. Similarly, some BPGM ‐associated HE cases, including a patient with a homozygous nonsense mutation, have been associated with normal p50 results . It is important to note that HOA variants may not be detected by routine protein screening methods; however, the concurrent use of three methods, cation exchange HPLC, capillary electrophoresis, and mass spectrometry, detects all of the cases seen in our reference laboratory experience …”