MAPT and Huntington disease: Significant meta‐analyses are found for 24‐hydroxycholesterol (24‐OHC), 27‐hydroxycholesterol (27‐OHC), NfL, and T‐tau (total tau) in early‐stage HD and for cortisol, high‐density lipoprotein (HDL), mutant huntingtin (mHTT), and HTT in mid‐stage HD after clinical motor diagnosis.