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Aids in diagnosing enterovirus infections
Enteroviruses are positive-sense RNA viruses in the Picornaviridae family. These viruses were initially classified by serotype as polioviruses (3 types), echoviruses (31 types, including types 22 and 23, which are now classified as parechoviruses), coxsackievirus A (23 types), and coxsackievirus B (6 types). However, genomic studies have demonstrated that there is significant overlap in the biological characteristics of different serotypes and, more recently, isolated enteroviruses are now named with consecutive numbers (eg, EV68, EV69).
The normal site of enterovirus replication is the gastrointestinal tract where the infection is typically subclinical. However, in a proportion of cases, the virus spreads to other organs, causing systemic manifestations, including mild respiratory disease (eg, common cold); conjunctivitis; hand, foot, and mouth disease; aseptic meningitis; myocarditis; and acute flaccid paralysis. Collectively, enteroviruses are the most common cause of upper respiratory tract disease in children. In addition, the enteroviruses are the most common cause of central nervous system (CNS) disease; they account for almost all viruses recovered in culture from spinal fluid. Differentiation of enteroviruses from other viruses and bacteria that cause CNS disease is important for the appropriate medical management of these patients.
Traditional cell culture methods require 6 days, on average, for enterovirus detection. In comparison, real-time PCR allows same-day detection. Detection of enterovirus nucleic acid by PCR is also the most sensitive diagnostic method for the diagnosis of CNS infection caused by these viruses.
A positive result indicates the presence of enterovirus RNA in the specimen.
A negative result does not rule out the possibility of enterovirus infection. This assay may detect virus from a variety of specimen types in asymptomatic individuals. This assay should only be used for patients with a clinical history and symptoms consistent with enterovirus infection, and must be interpreted in the context of the clinical picture. This test should not be used to screen asymptomatic patients.
Accuracy/Diagnostic Sensitivity and Specificity:
We compared the generic detection of enteroviruses from spinal fluid by conventional tube cell culture (MCR-5) and by LightCycler PCR. Of 715 specimens tested, enteroviruses were detected in 65 (9%) by conventional cell culture and 82 (11%) by LightCycler PCR. Twenty-two of 82 (27%) were exclusively positive by PCR; whereas, only 5 of 65 (8%) were exclusively positive by conventional cell cultures.
Supplemental Data (Spiking Studies):
To supplement the data above, 30 or more negative specimens of each specimen type (cerebrospinal fluid/sterile body fluid, dermal/ocular/rectal swabs, plasma, and upper and lower respiratory specimens) were spiked with enterovirus culture control at approximately 10 to 50 targets/mcL (the approximate limit of detection). The spiked specimens were run in a blinded manner along with negative (nonspiked) specimens of each specimen type. Of the spiked specimens, 97% to 100% were positive, and 100% of the nonspiked specimens were negative. A total of 489 spiked and nonspiked specimens were tested.
The assay detected all 64 members of an enterovirus panel, consisting of coxsackieviruses, polio viruses, echoviruses, and other enteroviruses.
Analytical Specificity/Limit of Detection (LoD):
The lower LoD of this assay is approximately 10 to 50 RNA target copies/mcL. This was confirmed in all specimen types accepted for this assay.
The assay did not crossreact with a specificity panel containing other RNA-containing viruses (rhinovirus; reovirus; influenza virus, types A and B; respiratory syncytial virus; and parainfluenza virus) and DNA-containing viruses (herpes simplex, Epstein-Barr virus, varicella-zoster virus, and cytomegalovirus).
This is a qualitative assay and results are reported a either negative or positive for targeted enterovirus RNA.
1. Enterovirus surveillance-United States, 1970-2005. MMWR Morb Mortal Wkly Rep Sept 15 2006;55(SS08):1-20
2. Foray S, Pailloud F, Thouvenot D, et al: Evaluation of combining upper respiratory tract swab samples with cerebrospinal fluid examination for the diagnosis of enteroviral meningitis in children. J Med Virology 1999;57(2):193-197
3. Furione M, Zavattoni M, Gatti M, et al: Rapid detection of enteroviral RNA in cerebrospinal fluid (CSF) from patients with aseptic meningitis by reverse transcription-nested polymerase chain reaction. New Microbiol 1998;21(4):343-351