Inflammation assessment in psoriatic arthritis via optical spectral transmission: correlations with clinical markers and musculoskeletal ultrasound.

OBJECTIVES

To assess the value of optical spectral transmission (OST) in detecting joint inflammation in patients with psoriatic arthritis (PsA) and to evaluate correlations of OST with musculoskeletal ultrasound (US) and clinical disease activity markers.

METHODS

OST and clinical examinations were performed on the finger (metacarpophalangeal, proximal-interphalangeal, distal-interphalangeal) and wrist joints of patients with PsA and healthy controls. A subset of patients was additionally examined via musculoskeletal US. OST differences in the two groups were statistically assessed and the diagnostic performance of OST was evaluated by Receiver-Operating-Characteristics (ROC). Additionally, associations between OST values and clinical, laboratory, as well as US activity markers were examined through correlation analyses and linear regression.

RESULTS

A total of 3,000 joints from 100 PsA patients were examined using OST and compared to 3,000 joints from 100 controls. OST was significantly higher in the PsA group compared to the control group (15.76 vs. 10.24; p<0.001). ROC (PsA vs. controls) revealed a very good diagnostic OST performance by an area-under-the-curve of 0.848 (95%-CI 0.795-0.900; p<0.001), with a sensitivity of 0.89 and specificity of 0.71 for an OST cut-off of 12.75. Among patients, OST correlated moderately with Joint-Power-Doppler- (rho=0.412; p=0.015) and Grey-Scale-US (rho=0.419; p=0.014), respectively. Moreover, significant OST correlations with CRP (rho=0.232; p=0.021), ''Disease-Activity-in-Psoriatic-Arthritis (DAPSA)'' (rho=0.215; p=0.032) and "Disease-Activity-Score-28 (DAS28)" (rho=0.23; p=0.021) were found.

CONCLUSION

OST associated significantly with clinical, US and laboratory disease activity markers in patients with PsA. Furthermore, OST could reliably differentiate between sonographically inflamed and non-inflamed joints in patients with PsA.