Approach Considerations
While the diagnosis of pleurodynia is made on clinical grounds, several laboratory studies are useful. Negative serology does not exclude the disease. Virus isolation from stool, pleural fluid or the pharynx is most specific, but not sensitive, test and can render a positive result for up to 2 weeks after resolution of symptoms. Coxsackie virus B1-B6 is the most common isolated variant. [12] Necrosis of the striated intercostal muscles is visible. in histologic studies. Rarely, adjacent pleural inflammation results in a small exudative pleural effusion.
Laboratory Studies
Coxsackie B virus infection can be diagnosed by isolation of the virus in cell culture, detection of virus RNA via polymerase chain reaction (PCR) or serologic evaluation of viral antibodies. [14]
Serum creatine kinase is usually elevated because of muscle necrosis. The white cell count ranges from mild leukopenia to mild leukocytosis. Although seldom performed for the diagnosis of pleurodynia per se, tissue diagnosis can be made by direct detection of the viral antigen or by isolation of RNA virus-specific sequences. Depending on the clinical presentation and suspicion for serositis caused by systemic lupus erythematosus, an antinuclear antibody test can be performed.
Viral cultures
Primary monkey kidney cells or embryonic lung fibroblasts are the standard cells used for isolation and identification of coxsackievirus B. The addition of Buffalo green monkey kidney cells may increase the sensitivity of this method. Viral growth occurs in 1-4 days, causing a cytopathic effect on the host cells, resulting in rounded, refractile cells that eventually lyse. The cultures may be performed from various clinical specimens, dictated by the presence of clinical symptoms.
Throat viral cultures are more sensitive than urine viral cultures and confirm 33% of the enteroviral infections studied. Throat culture findings were positive for coxsackievirus B in 45% of the patients presenting with pleurodynia. Blood cultures are useful in children younger than 3 months. Stool cultures have a higher yield than rectal swabs. Having multiple culture specimens may also increase the yield of virus recovery in culture.
A positive enteroviral culture result must be interpreted in light of the clinical context and the history of polio immunization. After vaccination with the live attenuated oral polio vaccine, viral culture results from both throat and stool specimens may remain positive for enteroviruses for several months. Similarly, patients with asymptomatic infections may shed the virus for months after they acquire the infection.
Cerebrospinal fluid (CSF) viral cultures have limited clinical utility in the management of enteroviral meningitis due to poor sensitivity (65-75%), high cost, and long turnaround time.
Fluorescent staining and neutralization assays
Using specific antibodies, these tests are used to further confirm and delineate the type of enterovirus isolated from cell culture.
Molecular diagnosis
Molecular methods may soon replace viral culture and neutralization assays used to isolate and type enteroviruses. Viral culture and neutralization assays are reliable but time-consuming and costly methods.
Reverse transcriptase PCR (RT-PCR) is now an established technique for the detection of viral nucleic acids, especially from specimens with a low viral load that may be associated with false-negative cell culture results. [15] In the CSF, RT-PCR has better sensitivity than viral culture. In children, RT-PCR for throat specimens was also more sensitive than viral culture. Another advantage is the rapid turnaround time, which has resulted to improved health care costs, especially in the management of enteroviral meningitis. [16, 17]
Commercial diagnostic RT-PCR kits are available for the identification of coxsackievirus B RNA. One disadvantage of RT-PCR is that the virus serotype cannot be identified. Additional restriction fragment length polymorphism (RFLP) assays may provide a simple strategy to identify the virus subtype. [18]
Reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay is a rapid, in vitro technique based on viral RNA amplification, targeting highly conserved regions in 5’ URT gene. In one study of 150 CSF and stool samples, the results were compared with those from RT-PCR. RT-LAMP assay showed high sensitivity and specificity in isolating and typing coxsackieviruses. [19]
Specific antibodies against enteroviral groups and serotypes are commercially available, but their application has thus far been limited to fluorescent staining and detection of viral antigens in cell cultures, rather than clinical specimens.
Enzyme-linked immunosorbent assay (ELISA) is more sensitive than the neutralization test and can be used as a screening tool, followed by the neutralization test for confirmation. ELISA using an enteroviruses group–specific monoclonal antibody may detect early immunoglobulin M (IgM) antibody secreted during coxsackievirus B infection. The test is more sensitive than the neutralization tests and can be used as a screening tool, followed by the neutralization test. The specificity is not extremely high because the antibodies cross-react with other enteroviruses such as hepatitis A virus. [20, 21]
The neutralization assay measures the ability of the serum to antagonize the viral infectivity in cell culture. The cytopathic effect-based neutralization test (Nt-CPE) and the plaques reduction neutralization test (PRNT) are the most common methods for quantifying the neutralizing antibody titers. [22, 23] Although the tests are expensive and laborious, a more specific finding of a positive ELISA result followed by a negative neutralization test result usually signifies an enteroviral infection other than that caused by coxsackievirus B. An efficient neutralization test based on the enzyme-linked immunospot assay (Nt-ELISPOT) has shortened the testing period from 7 days to approximately 20 hours, with good correlation (r2=0.9462) between the Nt-ELISPOT and the Nt-CPE assays. This modified Nt-ELISPOT would allow for faster specimen processing in coxsackievirus B vaccine trails, which require testing of a large number of serum specimens. [24]
Imaging Studies
Chest radiography
A chest radiograph is usually obtained to exclude other causes of chest pain. In pleurodynia, the findings on chest radiography can be normal, or the radiograph may show a small amount of ipsilateral pleural effusion or adjacent atelectasis from splinting. The atelectasis can be linear or in the form of bibasilar consolidation. Infrequently, the coxsackievirus B infection causes pneumonia, with a radiographic pattern of fine perihilar opacities.
