Background With the recent introduction of biological drugs, remarkable improvements have been reported in treatment of ankylosing spondylitis (AS). Since those are most effective for delaying the progression when started sufficiently early in the disease course, more aggressive interventions are necessary at that time through evaluation of disease activity. Usually three methods for disease activity assessment are available for use in patients with AS: BASDAI (Bath AS Disease Activity Index), BASFI (Bath AS Disease Functional Index), and ASDAS (Ankylosing Spondylitis Disease Activity Score). However, these activity score have problem of depending too much on subjective assessment. Laboratory findings such as ESR and CRP also are not the good biomarkers since they have possibility of false positive and false negative. Thus, there is a high demand for additional and complementary marker that correlate with disease activity. Platelet distribution width (PDW) is specific marker of platelet activation. It can represent the heterogeneity of thrombocyte volume. Mean value of PDW was significantly higher in patients with preterm labor with asserted platelet activation compared to healthy persons suggesting the possible high grade inflammation in the pathology. In addition, an association between elevated platelet (PLT) counts and several autoimmune diseases is well known.
Objectives We investigated whether PDW and PLT counts correlated with disease activity indices of AS and laboratory inflammatory markers and compared them between active and inactive AS patients.
Methods We evaluated the disease activity in the 78 AS patients by using the BASDAI, ASDAS-ESR, and ASDAS-CRP. Laboratory inflammatory marker as acute-phase reactants, including ESR, and CRP levels were also measured in these AS patients. We divided all patients into 2 groups according to disease activity indices of AS: active groups were defined as BASDAI ≥3.7 (the median), ASDAS-ESR ≥2.1 (60.2%) and ASDAS-CRP ≥2.1 (43.6%).
Results The mean (±SD) PDW was 11.0 (±1.3) %. The means (±SD) of PLT counts, ESR, CRP, BASDAI, ASDAS-ESR, and ASDAS-CRP level were respectively 263±57 x 109/L, 21 (±18.6) mm/hr, 5.17 (±8.0) mg/l, 3.6 (±1.8), 2.39 (±1.03), and 2.08 (±1.02)] in the patients with AS (not shown). PDW significantly correlated with BASDAI, ASDAS-ESR, and ASDAS-CRP (r =0.390, p<0.01; r =0.287, p<0.05; r =0.295, p<0.001, respectively). On the other hand, PLT count showed no significant correlation with these parameters, but there was significant correlations with CRP (r =0.346, p<0.05) (Table). The Mean of PDW of patients with higher BASDAI were significantly higher when compared with that with lower activity (11.4±1.4 vs 10.6± 1.0%, p=0.007) (Figure).
Conclusions To conclude, we suggest PDW as supplementary novel marker to detect active AS that shows conventional inflammatory marker in normal range.
Disclosure of Interest None declared