الفهرس 
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Abstract
Psoriatic arthritis (PsA) is a chronic autoimmune disease characterised by joint inflammation and psoriatic skin changes. The manifestations of PsA are diverse involving peripheral joints, entheses, dactylitis and axial skeleton.
Psoriatic arthritis is a distinctive form of inflammatory arthritis which can occur in association with psoriasis. Though it is now recognized as a separate disease entity from other inflammatory arthritic disorders, yet, it is considered a part of the seronegative spondyloarthropathy family with the characteristic inflammatory manifestations of both spinal and peripheral joints.
The diagnosis of PsA may be missed because the patients commonly presented by symptoms other than frank arthritis. The most sensitive and specific criteria that is available to date is the Classification Criteria for Psoriatic Arthritis (CASPAR).
Early diagnosis and treatment result in better outcomes for patients with PsA in terms of joint function and erosive joint disease.
Chitinase-3-like protein 1 (YKL-40), a 39 kD heparin and chitin binding glycoprotein, is a novel potential biomarker of inflammatory processes, which is expressed and secreted by immune cells such as activated macrophages and neutrophils. It is hypothesized that YKL-40 participates in acute and chronic inflammations, based on the fact that this glycoprotein is over-expressed in pathological conditions associated with active inflammatory processes.
Our aim was designed to evaluate the role of YKL-40 as a diagnostic biomarker in PsA patients and determine its value in assessment of disease activity and severity in PsA patients.
We conducted this study on 25 PsA patients, and 25 normal healthy individuals served as a control group. The patients and control groups were subjected to full history taking, thorough clinical examination and laboratory investigations.
Serum levels of YKL- 40was measured in all patients and control groups using ELISA technique.
The present study revealed:
- Significantly higher plasma levels of YKL- 40 in
patients compared to the controls.
- Statistically significant positive correlation between YKL- 40 levels and PASI score thus it can be a promising severity marker of psoriatic lesions if validated in larger scale studies.
- Statistically significant positive correlation between YKL- 40 levels and DAPSA score thus it can support the hypothesis that the serum concentration of YKL-40 reflects the activity of PsA.
- We concluded that: The patients with PsA had elevated levels of serum YKL- 40 compared to controls. It was also found that serum YKL- 40 has high specificity (92%) and sensitivity (96%) in diagnosis of PsA. Also, YKL- 40 showed high negative predicting value (NPV) and positive predicting value (PPV) of 95.8% and 92.3% respectively as a predictor for patients with PsA. These results are implicating strong ability of serum YKL- 40 to be a new inflammatory biomarker associated with PsA. In addition, it was found that serum YKL- 40 concentrations significantly correlated with the disease activity and severity of psoriatic lesions in PsA patients. So, the results of this study suggested that the addition of YKL- 40 as a serological marker has a valuable role in diagnosis of PsA and reflection of disease activity and severity.