Approach To Investigations In A Patient of Musculoskeletal Disorder
February 14, 2008 by Dr Arun Pal Singh
Filed under Clinical Evaluation
Majority of musculoskeletal disorders can be diagnosed easily by a complete history and physical examination.
Clinical evaluation helps to determine whether additional investigations are needed.
Monarticular conditions require additional evaluation, as do traumatic of inflammatory conditions and conditions accompanied by neurologic changes or systemic manifestations of serious disease.
Individuals with chronic symptoms are candidates for additional evaluation.
The extent and nature of the additional investigation should be dictated by the clinical features and suspected pathologic process.
Routine investigations include
- Complete blood count including a white blood cell and differential count,
- Erythrocyte sedimentation rate (ESR)
- C-reactive protein (CRP)
- Both tests are inexpensive and easily performed
The CRP and ESR values may be elevated with infections, inflammatory arthritis, autoimmune disorders, neoplasia, pregnancy, and advanced age.
Serologic tests for rheumatoid factor, antinuclear antibodies, complement levels, Lyme disease antibodies, or antistreptolysim O (ASO) titer should be carried out only when there is substantive clinical evidence suggesting a relevant diagnosis.
IgM rheumatoid factor (autoantibodies against the Fc portion of IgG) is found in 80 percent of patients with RA and may also be seen in low titers in patients of
- chronic infectionsi.e.tuberculosis, leprosy
- Autoimmune disease i.e. SLE, Sjogren’s syndrome
- Chronic pulmonary, hepatic, or renal disease.
Antinuclear antibodies are found in nearly all patients with SLE and may also be seen in patients with other autoimmune diseases, drug-induced lupus or chronic hepatitic or renal disorders.
Aspiration and analysis of synovial fluid is always indicated in acute monarthritis or when an infectious or crystal-induced arthropathy is suspected.
Synovial fluid analysis
Synovial fluid analysis may be crucial in distinguishing between noninflammatory and inflammatory processes. This distinction can be made on the basis of the appearance, viscosity, and cell count of the synovial fluid.
Tests for synovial fluid glucose, protein, lactate dehydrogenase, lactic acid, or autoantibodies are not recommended, as they are insensitive or have little discriminatory value.
Noninflammatory synovial fluid is clear, viscous, and amber-colored, with a white blood cell count of <2000/µL and a predominance of mononuclear cells. The viscosity of synovial fluid is assessed by expressing fluid from the syringe one drop at a time. Normally there is a stringing effect, with a long tail behind each drop. Effusions due to osteoarthritis or trauma usually have this typical viscosity.
Inflammatory fluid is turbid and yellow, with an increased white cell count and a predominance of polymorphonuclear leukocytes. Inflammatory fluid has a reduced viscosity, with little or no tail following each drop of synovial fluid. Such effusion are found in RA, gout, other inflammatory arthritis, and septic arthritis.
Infectious fluid is turbid and opaque, with a white cell count usually >50,000/µL, a predominace of polymorphonuclear leukocytes (>75%), and low viscosity. Such effusions are typical of septic arthritis, but they occur rarely with sterile inflammatory arthritides such as RA or gout.
Hemorrhagic synovial fluid may be seen with hemarthrosis or trauma. Synovial fluid should be analyzed immediately for appearance, viscosity, and cell count. Cellularity and the presence of crystals may be assessed by light or polarizing microscopy, respectively.
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