URINALYSIS AND BODY FLUIDS SYNOVIAL FLUID LECTURE ONE

URINALYSIS AND BODY FLUIDS (SYNOVIAL FLUID) LECTURE ONE Dr. Essam H. Jiffri 1

Synovial Fluid - Synovial fluid, referred to as "joint fluid" is a viscous liquid found in the joint cavities. 2

Synovial Fluid - It is formed as an ultrafiltrate of the plasma across the synovial membrane, which mucopolysaccharide containing hyaluronic acid and a small amount of protein is secreted by the cells of the synovial membrane. 3

Synovial Fluid - Except for high-molecular weight proteins, the plasma filtration is nonselective; therefore, normal synovial fluid has essentially the same chemical composition as the plasma. - Synovial fluid supplies nutrients to the cartilage and acts as a lubricant to the surfaces of the frequently moving joints. 4

COLLECTION - The fluid is found in all joints, the specimen usually received in the laboratory is an aspirate of the knee. - Synovial fluid is collected by needle aspiration, called arthrocentesis. - The normal amount of fluid contained in the knee cavity is less than 3. 5 ml, this amount increases in disorders of the joints. 5

COLLECTION - Normal synovial fluid will not clot; however, fluid from a diseased joint may contain fibrinogen and form a clot. - Recommended specimen containers include: Ø Ethylene diamine tetraacetic acid (EDTA) tube for cell counts and differentials. Ø Heparinized tube for chemical and immunologic tests. Fluid for complement studies should be frozen before storage. Ø Plain, sterile tube for microbiologic testing and crystal examination. 6

COLLECTION - Analysis of synovial fluid is used to classify joint disorders in terms of their pathologic origins. - Five commonly used categories associated with fluid buildup and arthritis and their clinical significance are: 7

Clinical and Pathologic Significant of Joint Disorders _________________________ Group Classification Pathologic Significance _________________________ I. Noninflamatory II. Inflammatory III. Septic IV. Crystal-induced V. Hemorrhagic 8 Degenerative joint disorders Immunologic problems, including: rheumatoid arthritis and lupus erythematosus Microbial infection Gout Pseudogout Traumatic injury Coagulation deficiencies

COLLECTION - Results from both synovial fluid and blood analyses must be considered along with the patient's clinical history before a category is assigned. 9

SYNOVIAL FLUID IN THE CHEMISTRY LABORATORY - Because synovial fluid is chemically an ultrafiltrate of plasma, chemistry test values are approximately the same as serum values, few chemistry tests are considered clinically important. 10

SYNOVIAL FLUID IN THE CHEMISTRY LABORATORY - Normal synovial fluid glucose should not be more than 10 mg per dl lower than the blood value. - Synovial fluid lactate levels below 7. 5 mmol/L provide a 98 percent for septic arthritis; whereas levels above 7. 5 mmol/L are found consistently with septic arthritis but may also be seen in rheumatoid arthritis. 11

SYNOVIAL FLUID IN THE CHEMISTRY LABORATORY - Other chemistry tests that may be requested are the total protein and uric acid determinations. - Because the large protein molecules are not filtered through the synovial membranes, normal synovial fluid contains less than 3 g/dl of protein. - Increased levels are found in inflammatory and hemorrhagic disorders. 12

SYNOVIAL FLUID IN THE CHEMISTRY LABORATORY - The elevation of serum uric acid in cases of gout is well known; therefore, demonstration of an elevated synovial fluid uric acid may be used to confirm the diagnosis. 13

SYNOVIAL FLUID IN THE SEROLOGY LABORATORY - Serology laboratory plays an important role in the diagnosis of joint disorders. - The majority of the tests are performed on serum, with actual analysis of the synovial fluid serving as confirmatory measure in cases that are difficult to diagnose. 14

SYNOVIAL FLUID IN THE SEROLOGY LABORATORY - The autoimmune diseases rheumatoid arthritis and lupus erythematosus cause very serious inflammation of the joints and are diagnosed in the serology laboratory by demonstrating the presence of their particular autoantibodies in the patient's serum. 15

SYNOVIAL FLUID IN THE SEROLOGY LABORATORY - Determination of synovial fluid complement levels can be an aid in the differential diagnosis of arthritis as to immunologic and non-immunologic origin. - Measurement of the complement components Clq, C 4, C 2, and C 3 is performed primarily by single radial immunodiffusion. 16