Participant demographics
| Covariate | ALS cases (n=125) | Controls (n=71) | P value |
| Age at plasma collection (years)* | 63.0 (53.0–69.0) | 61.0 (53.0–65.0) | 0.362 |
| Sex | 0.972 | ||
| Female | 51 (40.8) | 28 (39.4) | |
| Male | 74 (59.2) | 43 (60.6) | |
| BMI at study entry (kg/m2)† | 25.6 (22.8–29.6) | 26.6 (23.9–30.3) | 0.116 |
| Smoking | 0.569 | ||
| Non-smoker | 68 (54.4) | 33 (46.5) | |
| Former smoker | 43 (34.4) | 26 (36.6) | |
| Current smoker | 13 (10.4) | 10 (14.1) | |
| Missing | 1 (0.8) | 2 (2.8) | |
| Family history of ALS | |||
| No | 111 (88.8) | ||
| Yes | 10 (8.0) | ||
| Missing | 4 (3.2) | ||
| Age at diagnosis (years) | 62.2 (52.7–68.7) | ||
| El Escorial criteria | |||
| Suspected | 3 (2.4) | ||
| Possible | 19 (15.2) | ||
| Probable, LS | 37 (29.6) | ||
| Probable | 42 (33.6) | ||
| Definite | 23 (18.4) | ||
| Missing | 1 (0.8) | ||
| Onset segment | |||
| Bulbar | 38 (30.4) | ||
| Cervical | 38 (30.4) | ||
| Lumbar | 49 (39.2) | ||
| Time between diagnosis and blood draw (years)* | 0.57 (0.36–0.75) | ||
| Time between symptom onset and diagnosis (years) | 1.01 (0.68–1.51) | ||
| PEG tube present (%) | 6 (4.8) |
Table of descriptive statistics for the overall participant study population. Continuous variables represented as the median (25th–75th percentile) and for categorical variables as n (%). P values correspond to Wilcoxon rank-sum tests for continuous variables and χ2 tests for categorical variables. C9orf72 status and ALS family history do not have p values because counts were too small for hypothesis testing.
*Median, 25th percentile and 75th percentile are computed using 123 cases and 69 controls (2 cases and 2 controls are missing).
†Median, 25th percentile and 75th percentile are computed using 117 cases and 61 controls (8 cases and 10 controls are missing).
ALS, amyotrophic lateral sclerosis; BMI, body mass index; GED, Graduate Equivalency Diploma; HS, high school; LS, lab supported; m, metres; NA, not available; PEG, percutaneous endoscopic gastrostomy.