Table 2.

Rate of changes in the binary sacroiliac joint outcome measure

Outcome	X-ray intervals of 2 years ± 6 months 894 intervals in 515 patients
	Intervals with potential progression N=703	Intervals with potential regression N=867
Main analysis: 2 readers*
Progression	24 (3.4%)
Regression		1 (0.12%)
Sensitivity analysis: integrating a third scoring†
Progression	105 (14.9%)
Regression		21 (2.4%)

*Change considered on agreement of both primary readers.

†Change considered on agreement in 2/3 readings. Progression defined as worsening of at least one grade in at least one SIJ and ignoring a change from 0 to 1 over 2 years; regression defined as improvement of at least one grade in at least one SIJ and a baseline value of at least two in the improved joint.