LRRK2 and Parkinson disease: By contrast, analyzing cytochrome c oxidase activity relative to citrate synthase activity did not reveal differences between the two groups (LRRK2+/PD−, median: 0.035, IQR: 0.027–0.040; LRRK2+/PD+, median: 0.023, IQR: 0.014–0.037; Mann–Whitney test: p = 0.114) (Figure 1B).