Laboratory Studies
Parvovirus B19
The incubation period for parvovirus B19 is 7-18 days, and the state of viremia lasts 5-6 days. The following studies are indicated:
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Complete blood count (CBC) to assess hemoglobin, neutrophils, and lymphocytes
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Immunoglobulin M (IgM) antibody titer – High levels may be noted 4-6 days after the initial viremia
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Viral B19 DNA by polymerase chain reaction (PCR)
The immunoglobulin G (IgG) antibody titer is of little diagnostic significance. Low-to-moderate titers for rheumatoid factor (RF), anti-DNA, antinuclear antibodies (ANAs), and anticardiolipin antibodies are possible in some patients.
Hepatitis viruses
The following tests may be ordered for hepatitis A virus (HAV):
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Bilirubin and transaminase levels – These are typically elevated
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IgM-specific anti-HAV
The following tests may be ordered for hepatitis B virus (HBV):
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Bilirubin and transaminase levels – These are commonly elevated but may be normal in the early stage of disease when arthritis is present
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Serum hepatitis B surface antigen (HBsAg), hepatitis B early antigen (HBeAg), anti-HBsAg IgM (indicative of acute infection), viral DNA, and PCR
The following tests may be ordered for hepatitis C virus (HCV):
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Bilirubin and transaminase levels – These are typically elevated, but normal transaminase levels do not exclude HCV infection
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Anti-HCV
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HCV-RNA by PCR
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Cryoglobulins and RF
Rubella virus
The following tests may be ordered for rubella virus:
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Anti–rubella virus IgM – This value peaks 8-21 days after symptoms, then wanes by 5 weeks
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Anti–rubella virus IgG – This value rises rapidly over a period of 1-3 weeks, and the rise is of long duration
Rubella virus has been isolated from lymphocytes and synovial fluid of patients who had vaccine-induced disease or who experienced rubella virus–associated arthritis years earlier.
Alphaviruses
Diagnosis of alphavirus infection is confirmed by specific serology results.
Retroviruses
In persons with HIV infection, laboratory abnormalities generally are common but nonspecific, including the following:
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Elevated levels of serum immunoglobulins
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Moderately elevated erythrocyte sedimentation rate (ESR)
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Circulating immune complexes
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Low-grade complement activation
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Low-titer ANA
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RF
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False-positive test result for syphilis and anticardiolipin antibodies
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Lupus anticoagulants
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Possible detection of CD8 + T cells and P-24 antigen in synovial fluid
Human T-lymphotropic virus (HTLV-1) infection is diagnosed on the basis of detection of antibodies by means of enzyme-linked immunosorbent assay (ELISA), with confirmation by Western blot and the observation of “flower cells” on the peripheral smear.
Other Tests
Radiologic findings in patients with viral arthritis depend on the specific condition. Most of the virus-associated arthropathies are nonerosive and show only soft-tissue swelling. However, with HIV-related seronegative or psoriatic-type arthropathy, erosions, ankylosis, narrowing of joint spaces, whittling, osteolytic lesions, periostitis, sacroiliac joint-space widening, and syndesmophyte formation can be seen.
Aspiration of the joint is useful to help rule out other conditions, such as crystal arthropathy or bacterial infection.
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Viral arthritis. Typical "slapped cheek" appearance. Courtesy of Brenda Moroz, MD, Montreal Children's Hospital.
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Viral arthritis. "Slapped cheeks" with typical reticulated erythema of arms. Courtesy of Brenda Moroz, MD, Montreal Children's Hospital.
