Background/Purpose

Axial spondyloarthritis (ax-SpA) consisted patients with advanced axial SpA or ankylosing spondylitis (AS) and non-radiographic axial SpA (nr-axSpA). Evaluation of disease activity in axSpA is complex due to the phenotypic heterogeneity of the disease. Assessment in Spondyloarthritis international Society (ASAS) endorsed the cut off values for ASDAS-CRP. The aim of this study was to assess the validity of AS Disease Activity Score (ASDAS)-CRP and ASDAS-ESR as clinical tools for assessing disease activity in axSpA and to estimate the cut-off values of ASDAS-CRP and ASDAS-ESR for male and female patients with axSpA.

Methods

Patients with axSpA were recruited from Erciyes Spondyloarthritis Cohort (ESPAC) and assessed for BASDAI, ASDAS, BASFI, BASMI, Ankylosing Spondylitis Quality of Life (ASQoL), and VAS-pain. Patients were grouped into low and high disease activity according to the physician’s (DrG) and patient’s global (PtG) assessment score (>6/10 vs <4/10), ASAS partial remission criteria, treatments and presence of peripheral arthritis. The discriminant ability of ASDAS-CRP and ASDAS-ESR was assessed using standardized mean differences. Receiver operating characteristic (ROC) curves were used for comparisons. Optimal cut-off values of ASDAS-CRP and ESR were calculated for both genders and for the whole group.

Results

Three hundred fifty-eight patients with axSpA (138 F, 220 M) were included in this study. One hundred sixty two patients met criteria for non-radiographic axSpA (nr-axSpA) and 196 for ankylosing spondylitis. Two ASDAS versions and BASDAI had good correlations with PtG and DrG in both groups, however correlation coefficients were relatively higher in men. Women had significantly higher VAS-pain, BASDAI item scores, PG and DrG and ESR. Discriminant ability of ASDAS-CRP, ASDAS-ESR and BASDAI were similar in men and women when patients were assigned into low and high disease activity based on the ASAS partial remission, PtG and DrG scores (assessed by comparing AUC of ROC curves). ASDAS cut-off values are quite similar in all groups indicating that ASDAS-CRP works similarly well in male and female patients with axSpA. The calculated ASDAS-CRP cut-offs in both genders were very similar to predefined values by ASAS except the cut off for in-active to moderate disease activity. The cut-off values for ASDAS-ESR seem to be lower than predefined values and women tent to have higher cut-offs compared to males.  

Conclusion

The construct validity of ASDAS-CRP to discriminate low and high disease activity and cut off values are similar in male and female patients with axSpA, however cut offs for ASDAS-ESR need to be redefined.

		ASDAS-CRP			ASDAS-ESR
	In-active-moderate	Moderate-High	High-Very high	In-active-moderate	Moderate-High	High-Very high
Whole group	1.57-1.69	1.93-2.34	3.40-3.92	1.43	1.82-2.06	3.25-3.57
Females	1.55-1.73	2.00-2.33	3.34-3.83	1.69-1.76	1.99.2.09	3.30-3.66
Males	1.56-1.73	1.91-2.41	3.48-3.96	1.32-1.36	1.61-2.03	3.17-3.55

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/is-there-any-gender-specific-difference-in-the-cut-off-values-of-ankylosing-spondylitis-disease-activity-score-asdas-in-patients-with-axial-spondyloarthritis/