Table 3.
Properties of ankle sensor features and models
| Sensor | Feature name | Statistic | SM duration group | Direction of motion group | Relationship with SARA (BARS) | Relationship with PROM-Ataxia | Test–retest reliability | Disease versus control | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Total | Gait subscore | Total | Gait subset | ||||||||||||
| r | P-value | r | P-value | r | P-value | r | P-value | ICC | P-value | es | |||||
| Ankle (single features) | SM distance | Mean | Long | PC1 | −0.39 (−0.38) | 3.0E-02 | −0.35 (−0.40) | 5.0E-02 | −0.60 | 4.0E-04 | −0.54 | 2.0E-03 | 0.94 | n.s. | - |
| Mean | Long | PC2 | −0.55 (−0.54) | 2.0E-03 | −0.51 (−0.55) | 3.0E-03 | −0.68 | 4.0E-05 | −0.65 | 9.0E-05 | 0.95 | 2.0E-02 | 1.2 | ||
| Mean | Short | PC1 | −0.62 (−0.64) | 2.0E-04 | −0.69 (−0.68) | 2.0E-05 | −0.47 | 7.0E-03 | −0.53 | 3.0E-03 | 0.94 | 2.0E-02 | 1.1 | ||
| Mean | Short | PC2 | −0.74 (−0.76) | 3.0E-06 | −0.79 (−0.80) | 2.0E-07 | −0.62 | 3.0E-04 | −0.66 | 6.0E-05 | 0.92 | 5.0E-03 | 1.5 | ||
| SD | Long | PC1 | - | n.s. | - | n.s. | −0.58 | 6.0E-04 | −0.50 | 4.0E-03 | 0.89 | n.s. | - | ||
| SD | Long | PC2 | −0.43 (−0.44) | 2.0E-02 | −0.41 (−0.46) | 2.0E-02 | −0.66 | 7.0E-05 | −0.59 | 5.0E-04 | 0.87 | n.s. | - | ||
| SD | Short | PC1 | −0.69 (−0.72) | 2.0E-05 | −0.75 (−0.76) | 2.0E-06 | −0.60 | 4.0E-04 | −0.64 | 2.0E-04 | 0.91 | 2.0E-02 | 1.2 | ||
| SD | Short | PC2 | −0.79 (−0.80) | 9.0E-07 | −0.83 (−0.85) | 4.0E-08 | −0.74 | 4.0E-06 | −0.75 | 4.0E-06 | 0.89 | 5.0E-03 | 1.7 | ||
| SM velocity | Mean | Long | PC1 | −0.63 (−0.63) | 2.0E-04 | −0.61 (−0.66) | 2.0E-04 | −0.77 | 2.0E-06 | −0.72 | 9.0E-06 | 0.95 | 1.0E-02 | 1.3 | |
| Mean | Long | PC2 | −0.78 (−0.78) | 8.0E-07 | −0.76 (−0.80) | 7.0E-07 | −0.80 | 4.0E-07 | −0.81 | 3.0E-07 | 0.95 | 1.0E-02 | 1.7 | ||
| Mean | Short | PC1 | −0.58 (−0.61) | 6.0E-04 | −0.66 (−0.66) | 4.0E-05 | −0.39 | 3.0E-02 | −0.45 | 1.0E-02 | 0.95 | 2.0E-02 | 1.1 | ||
| Mean | Short | PC2 | −0.70 (−0.73) | 2.0E-05 | −0.77 (−0.78) | 4.0E-07 | −0.55 | 2.0E-03 | −0.61 | 4.0E-04 | 0.94 | 5.0E-03 | 1.5 | ||
| SD | Long | PC1 | −0.41 (−0.42) | 2.0E-02 | −0.42 (−0.47) | 2.0E-02 | −0.69 | 4.0E-05 | −0.60 | 4.0E-04 | 0.90 | n.s. | - | ||
| SD | Long | PC2 | −0.64 (−0.66) | 2.0E-04 | −0.65 (−0.70) | 5.0E-05 | −0.80 | 3.0E-07 | −0.75 | 3.0E-06 | 0.90 | 8.0E-03 | 1.4 | ||
| SD | Short | PC1 | −0.60 (−0.64) | 3.0E-04 | −0.70 (−0.70) | 2.0E-05 | −0.49 | 5.0E-03 | −0.53 | 2.0E-03 | 0.92 | 2.0E-02 | 1.2 | ||
| SD | Short | PC2 | −0.74 (−0.77) | 4.0E-06 | −0.82 (−0.84) | 4.0E-08 | −0.69 | 4.0E-05 | −0.71 | 2.0E-05 | 0.89 | 5.0E-03 | 1.7 | ||
| SM acceleration | Mean | Long | PC1 | −0.70 (−0.74) | 2.0E-05 | −0.74 (−0.76) | 2.0E-06 | −0.57 | 8.0E-04 | −0.57 | 8.0E-04 | 0.96 | 5.0E-03 | 1.6 | |
| Mean | Long | PC2 | −0.78 (−0.80) | 7.0E-07 | −0.81 (−0.83) | 6.0E-08 | −0.61 | 4.0E-04 | −0.65 | 9.0E-05 | 0.94 | 5.0E-03 | 1.8 | ||
| Mean | Short | PC1 | −0.46 (−0.50) | 8.0E-03 | −0.56 (−0.55) | 7.0E-04 | - | n.s. | - | n.s. | 0.96 | 2.0E-02 | 1.0 | ||
| Mean | Short | PC2 | −0.58 (−0.63) | 6.0E-04 | −0.68 (−0.68) | 2.0E-05 | −0.40 | 3.0E-02 | −0.46 | 8.0E-03 | 0.95 | 9.0E-03 | 1.3 | ||
| SD | Long | PC1 | −0.47 (−0.52) | 7.0E-03 | −0.56 (−0.58) | 7.0E-04 | −0.38 | 3.0E-02 | −0.36 | 4.0E-02 | 0.97 | 2.0E-02 | 1.3 | ||
| SD | Long | PC2 | −0.62 (−0.65) | 2.0E-04 | −0.71 (−0.72) | 7.0E-06 | −0.49 | 5.0E-03 | −0.50 | 4.0E-03 | 0.92 | 4.0E-03 | 1.5 | ||
| SD | Short | PC1 | - | n.s. | −0.42 (−0.41) | 2.0E-02 | - | n.s. | - | n.s. | 0.95 | n.s. | - | ||
| SD | Short | PC2 | −0.44 (−0.49) | 2.0E-02 | −0.57 (−0.58) | 7.0E-04 | −0.38 | 4.0E-02 | −0.40 | 3.0E-02 | 0.90 | 2.0E-02 | 1.2 | ||
| AI | Mean | N/A | N/A | −0.67 (−0.66) | 4.0E-05 | −0.73 (−0.76) | 3.0E-06 | −0.65 | 1.0E-04 | −0.68 | 4.0E-05 | 0.88 | 6.0E-03 | 1.5 | |
| Entropy | N/A | N/A | −0.72 (−0.72) | 8.0E-06 | −0.78 (−0.80) | 3.0E-07 | −0.65 | 9.0E-05 | −0.70 | 2.0E-05 | 0.93 | 8.0E-03 | 1.4 | ||
| Ankle (models) | Ataxia severity prediction model | 0.82 (0.83) | 4.0E-09 | 0.84 (0.88) | 4.0E-10 | 0.81 | 9.0E-09 | 0.81 | 7.0E-09 | 0.95 | 4.0E-04* | 1.8 | |||
| Self-reported function prediction model | 0.82 (0.82) | 3.0E-09 | 0.82 (0.86) | 4.0E-09 | 0.83 | 2.0E-09 | 0.83 | 2.0E-09 | 0.94 | 6.0E-04* | 1.6 | ||||
Relationships with ataxia rating scales and patient-reported function, test–retest reliability and disease versus control statistics are provided. Key features/models are bolded. Features that were significantly different between preataxic individuals and controls are marked in the disease versus control p-value column with an (*).. Relationships that are not significant are labelled as ‘n.s.’ AI, activity intensity; BARS, Brief Ataxia Rating Scale; ICC, intraclass correlation coefficient; es, effect size; PC, Principal Component; PROM-Ataxia, Patient-Reported Outcome Measure of Ataxia; r, Pearson correlation coefficient; SARA, Scale for the assessment and rating of ataxia; SD, standard deviation; SM, submovement.