LRRK2 and Parkinson disease: Furthermore, when LRRK2 mutation carriers were separated by clinical PD status and analysed by unpaired t-test there was also no difference between R1441G-PD manifesting and non-manifesting individuals (p = 0.23) or between G2019S-PD manifesting and non-manifesting individuals (p = 0.33) (Fig. 3a and Table 3).