Automated detection of near falls: algorithm development and preliminary results

BMC Research Notes

Table 1 Sensitivity and specificity for detecting near falls using single parameters.

Parameter	axis	NOT Near Fall mean	Near Fall mean	NOT Near Fall SD	Near Fall SD	threshold	Sensitivity (%)	Specificity (%)	Detection (%)**
Max*	V	0.45	0.83	0.20	0.30	0.56	90.48	81.89	20.46
Max	M-L	0.31	0.60	0.16	0.26	0.41	71.43	86.38	31.65
Max	A-P	0.33	0.48	0.17	0.22	0.38	52.38	73.80	54.35
Maxdiff	V	0.17	0.37	0.09	0.15	0.21	80.95	80.99	26.91
Maxdiff	M-L	0.15	0.36	0.10	0.26	0.17	76.19	75.60	34.09
Maxdiff	A-P	0.19	0.41	0.19	0.24	0.24	76.19	82.34	29.64
maxp2p	V	0.71	1.40	0.29	0.53	0.88	90.48	80.39	21.80
maxp2p	M-L	0.63	1.35	0.30	0.67	0.80	80.95	83.53	25.18
maxp2p	A-P	0.75	1.38	0.43	0.57	0.93	76.19	82.93	29.30
maxp2pdiff	V	0.34	0.69	0.19	0.26	0.48	85.71	88.02	18.65
maxp2pdiff	M-L	0.30	0.72	0.20	0.52	0.35	80.95	76.95	29.90
maxp2pdiff	A-P	0.42	0.86	0.36	0.48	0.52	80.95	81.59	26.49
Std	V	0.13	0.19	0.06	0.05	0.16	61.90	74.55	45.82
Std	M-L	0.11	0.16	0.04	0.05	0.13	66.67	79.94	38.90
Std	A-P	0.13	0.17	0.05	0.04	0.15	61.90	79.34	43.34
Step regularity	V	0.58	0.32	0.17	0.12	0.27	71.43	5.99	98.26
Stride regularity	V	0.54	0.27	0.16	0.15	0.22	61.90	5.69	101.72
Symmetry	V	1.13	1.36	0.39	0.57	1.24	61.90	79.79	43.13

The sensitivity and specificity values obtained for detecting near falls (n = 21) as compared to non-near falls (n = 668) using single parameters. Non-near falls included regular gait intervals combined with the irregular (non-near falls) intervals (e.g., kicks, stepovers, stops).
*Max = maximum acceleration amplitude; Maxdiff = maximum acceleration derivative; Maxp2p = maximum peak-to-peak acceleration amplitude; Maxp2pdiff = maximum peak-to-peak acceleration derivative; Std = standard deviation; V: vertical; M-L: medio-lateral; A-P: anterior-posterior.
** The detection % is the distance from the ideal ROC curve (the lower, the better).

ISSN: 1756-0500