Table 1. Characteristics of a nationwide cohort of patients with mitochondrial dysfunction by mode of ascertainment.
|
Subcohort A |
Subcohort B | |||
|---|---|---|---|---|
| Probands (n=61) | Tested relatives, clinic based (n=116) | Untested relatives, register based (n=134) | All (n=311) | |
| n (%) | n (%) | n (%) | n (%) | |
|
Type of mutation | ||||
| Maternally inherited mDNA | 32 (52.5) | 112 (96.6) | 134 (100) | 278 (89.4) |
| De novo mDNA | 8 (13.1) | 0 (0) | 0 (0) | 8 (2.57) |
| nDNA | 21 (34.4) | 4 (3.45) | 0 (0) | 25 (8.04) |
|
Sex | ||||
| Male | 29 (47.5) | 39 (33.6) | 69 (51.5) | 137 (44.1) |
| Female | 32 (52.5) | 77 (66.4) | 65 (48.5) | 174 (56.0) |
|
Year of birth | ||||
| Before 1950 | 12 (19.7) | 29 (25.0) | 22 (16.4) | 63 (20.3) |
| 1950–1969 | 23 (37.7) | 49 (42.2) | 21 (15.7) | 93 (29.9) |
| 1970–1989 | 13 (21.3) | 27 (23.3) | 44 (32.8) | 84 (27.0) |
| 1990–2011 | 13 (21.3) | 11 (9.48) | 47 (35.1) | 71 (22.8) |
|
Year of study entrya | ||||
| 1968–1972 | 0 (0) | 64 (55.2) | 45 (33.6) | 109 (35.1) |
| 1973–1982 | 0 (0) | 13 (11.2) | 22 (16.4) | 35 (11.3) |
| 1983–1992 | 0 (0) | 16 (13.8) | 28 (20.9) | 44 (14.2) |
| 1993–2002 | 19 (31.2) | 10 (8.62) | 27 (20.2) | 56 (18.0) |
| 2003–2011 | 42 (68.9) | 13 (11.2) | 12 (8.96) | 67 (21.5) |
Abbreviations: mDNA=mitochondrial DNA; nDNA=nuclear DNA.
Probands were classified as the first individual diagnosed in a family, tested relatives as relatives that had tested positive for the mutation found in the family proband and untested relatives as relatives with a direct maternal relationship identified through the family relations database (as defined in the methods section).
The majority of the cohort members who had undergone genetic testing were older at study entry, whereas the untested relatives were generally younger: median (inter quartile interval) age at study entry, probands=36.1 (18.7–50.9) years, tested relatives= 6.63 (0.0–26.5) years, untested relatives=0.0 (0.0–6.61) years. The differences reflect that time for entry into the study differed for the three groups in order to avoid survivor bias (see methods section).