Development of a clinical prediction algorithm for knee osteoarthritis structural progression in a cohort study: value of adding measurement of subchondral bone density

Table 3 Improvement measures comparing base and BMD models in primary analysis

Improvement measure	Outcome	Base model	BMD model	Comparison
Net reclassification improvement			Net % improvement	NRI (95% CI)
	OA progression	Ref	22%	0.49 (0.20, 0.77)
	No OA progression	Ref	27%
Integrated discrimination improvement		Base model average prediction	BMD model average prediction	IDI (95% CI)
	OA progression	0.12	0.16	0.04 (0.01, 0.06)
	No OA progression	0.09	0.09