Background/Purpose:  Ankylosing Spondylitis (AS) occurs more often in males than in females. Most women tend to have milder disease and may therefore be underdiagnosed. Male AS patients are more likely to develop radiographic spinal damage. The aim of the present study was to investigate whether there are differences in patient-reported assessments of disease activity, physical function, and quality of life between male and female patients with axial spondyloarthritis (SpA).

Methods: All consecutive patients from the Groningen Leeuwarden Axial SpA (GLAS) cohort who visited the outpatient clinic between January 2011 and December 2012 were included in this cross-sectional analysis. All patients fulfilled the modified New York criteria for AS (>90%) or the ASAS criteria for axial SpA. Disease activity was assessed using Bath AS Disease Activity Index (BASDAI), AS Disease Activity Score (ASDAS; calculated from BASDAI questions 2, 3 and 6, patient global assessment of disease activity (GDA), and, C-reactive protein (CRP)), swollen joint index (range 0-44), and tender joint index (range 0-46). Physical function was assessed using Bath AS Functional Index (BASFI) and quality of life using AS Quality of Life (ASQoL) questionnaire.

Results: Of the 469 included patients, mean age was 45 years (SD±13), mean duration of symptoms was 17 years (range 0-61), 66% were male, and 80% were HLA-B27+. Males were significantly older, had longer disease duration, and were more frequently HLA-B27+ compared to females. Extra-articular manifestations, comorbidity, and current use of NSAID, DMARD, and anti-TNF were comparable between both groups.

Patient-reported measures of disease activity (BASDAI, patient GDA, and tender joints) and outcome (BASFI and ASQoL) were significantly higher in female compared to male patients. ASDAS, capturing both subjective and objective aspects of disease activity, was also significantly higher in females. This difference can be explained by patient-reported aspects of the ASDAS, since CRP levels were comparable between male and female patients (Table 1). Differences remained statistically significant after correcting for age, disease duration, and HLA-B27 status.

Conclusion:  This cross-sectional study shows that patient-reported measures of disease activity and outcome as well as ASDAS were significantly worse in female axial SpA patients. It is important to be aware of these differences when interpreting patient-reported measures in research and clinical practice. These findings underline the importance of research into more balanced and objective markers of disease activity and outcome including biomarkers in axial SpA.

Table 1.Clinical assessments in male and female patients with axial SpA

	All patients (n=469)	Males (n=310)	Females (n=159)	P-value
BASDAI	3.6 (0.0-9.6)	3.4 (0.0-9.4)	4.2 (0.2-9.6)	0.000
ASDAS(CRP)	2.3 (0.0-5.7)	2.2 (0.0-5.2)	2.5 (0.6-5.7)	0.004
Patient GDA	4 (0-10)	3 (0-10)	5 (0-10)	0.001
CRP (mg/L)	3 (0-94)	3 (0-94)	3 (0-82)	0.415
CRP ≥5	176 (38%)	115 (38%)	61 (39%)	0.731
Swollen joints	0 (0-9)	0 (0-9)	0 (0-2)	0.576
≥1 swollen joint	18 (4%)	13 (4%)	5 (3%)	0.575
Tender joints	0 (0-22)	0 (0-22)	0 (0-19)	0.018
≥1 tender joint	108 (23%)	61 (20%)	47 (30%)	0.020
BASFI	3.3 (0.0-9.9)	3.0 (0.0-9.7)	4.0 (0.0-9.9)	0.030
ASQoL	6 (0-18)	4 (0-18)	7 (0-18)	0.000

Values are presented as median (range) or number of patients (%).

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/patient-reported-disease-activity-and-outcome-in-male-versus-female-patients-of-the-groningen-leeuwarden-axial-spondyloarthritis-glas-cohort/