الفهرس 
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Abstract
A
S is a common form of rheumatic diseases .It is a form of spondyloartritides. The earliest manifestation of AS is Sacroiliitis. The affection of peripheral joints and extramuskloskeletal may occur . Erosion of irregular manner and sclerosis are showed in the affected joints then gradually replaced by fibrocartilage then ossified. Permenant damage occurs due to these lesions in the spine, the junction of the annulus fibrosus of the disc cartilage and the margin of the vertebral bone . The outer annular fibres are replaced by bone and the vertebrae become fused. The fusion ascends the spine resulting in a tall bony column called “bamboo spine in late stages of the disease (Sieper et al., 2002).
Glycoside hydrolase18 is the family to which ,YKL-40 (CHI3L1) belongs. It binds to chitin, heparin, and hyaluronic acid, and its regulation is depend on various factors extracellular matrix changes, cytokines, growth factors, drugs and stress. CHI3L1 is synthesized and secreted by macrophages, chondrocytes, neutrophils, synoviocytes, , fibroblast-like cells, smooth muscle cells, and tumor cells. It plays a major role in tissue injury and repair inflammation, and remodeling responses (Zhao et al., 2020).
We aimed to study YKL-40 as an objective marker of ankylosing spondylitis disease activity.
This is a case control study conducted at outpatient clinic and inpatient department of physical medicine, rheumatology and rehabilitation in Ain Shams university hospitals. The study included 15 Ankylosing spondylitis patients diagnosed according to ASAS criteria (AKKOC and Khan, 2016) and 15 adult healthy volunteers as a control group.
All participants subjected to the following:
o Full medical history.
o Clinical examination:
• General
• Local (peripheral and axial joint examination).
o Assessment of disease activity by using:
a) ASDAS –CRP
b) BASDAI
c) BASMI
d) BASFI
o Laboratory investigation: For the assessment of serum YKL-40, venous blood samples were collected, then serum was separated.
The measurements were performed using enzyme-linked immunosorbent assay (ELISA).
Our result shows the following:
o Although YKL-40 showed 100% sensitivity and specificity still large scale studies with follow up of patients in response to drug treatment need to be done to assess its uses as a disease activity marker.
o Also large scale prospective studies are needed with the assessment of comorbidities and their time of development in correlation to YKL-40 as it has an excellent potential for perdiction of these comorbidities.
Conclusion
YKL-40 has 100% senstivity and 100% specificity so we can predict ankylosing spondylitis.
Recommendations
• YKL-40 proved to be a good diagnostic marker of ankylosing spondylitis with 100% senstivity and 100% specificity.
• YKL-40 is recommended in ankylosing spondylitis patients with comorbidities.
• YKL-40 is recommended in long term studies to asses the predictive value of it with cardiovascular diseases (central or peripheral).
• YKL-40 is recommended to be studied among relative of ankylosing spondylitis patients to asses the predictive value of it in developing the disease.
• YKL-40 is recommended to be studied in relation to enthesopathy scores.
CONCLUSION
YKL-40 has high senstivity and high specificity so we can predict ankylosing spondylitis.
RECOMMENDATIONS
• YKL-40 proved to be a good diagnostic marker of ankylosing spondylitis with high senstivity and high specificity.
• YKL-40 assessment is recommended in ankylosing spondylitis patients with comorbidities.
• YKL-40 is recommended in long term studies to asses the predictive value of it with cardiovascular diseases (central or peripheral).
• YKL-40 assessment is recommended to be studied among relative of ankylosing spondylitis patients to assess the predictive value of it in developing the disease.
• YKL-40 is recommended to be studied in relation to enthesopathy scores.