Rapid diagnosis of enterovirus infection by a new one-step reverse transcription-PCR assay

Enteroviruses and Parechoviruses

Infections with enteroviruses and human parechoviruses are highly prevalent, particularly in neonates, where they may cause substantial morbidity and mortality. Individuals with B-cell-related immunodeficiencies are at risk for severe enteroviral infections, usually a chronic and fatal meningoencephalitis. In transplant recipients and patients with malignancy, enterovirus infections typically involve the respiratory tract, but cases of severe, disseminated infection have been described. The mainstay of diagnosis for enterovirus and human parechovirus infections involves the use of molecular diagnostic techniques. However, routine nucleic acid-detection methods for enteroviruses will not detect human parechoviruses. Laboratory diagnosis of these viral infections is important in determining a patient's prognosis and guiding clinical management.

Enteroviral encephalitis in children: clinical features, pathophysiology, and treatment advances

Enteroviruses (EVs) have emerged as one of the important etiological agents as a causative organism for encephalitis, especially in children and adults. After the first report of EV encephalitis cases in 1950s, there have been increasing reports of regular outbreaks of EV encephalitis worldwide. Enteroviruses are RNA viruses of the family Picornaviridae that consists of more than 100 serotypes, which are characterized by a single positive-strand genomic RNA. The clinical features are pleomorphic and can be accompanied by mucocutaneous manifestations or isolated encephalitis only. The incidence of encephalitis in EV infection is reported to be about 3% and is associated with high mortality and morbidity. A number of newer therapeutic agents have been used in EV encephalitis with variable results. This review will focus on clinical features, pathophysiology, and newer treatment modality in EV encephalitis.

Democratizing molecular diagnostics: the GeneXpert(®) enterovirus assay

BACKGROUND

Few clinical scenarios are as diagnostically demanding as the workup of acute meningitis in the emergency room setting. In humans, most cases of meningitis are due to enteroviral infection, which usually resolves with supportive care and does not generally require hospitalization. The difficulty in evaluating meningitis is often related to its nonspecific presentation; rapid identification of the underlying etiologic agent is critical to selection of the most appropriate course of therapy.

OBJECTIVE

To develop a rapid, automated polymerase chain reaction-based test for enteroviral meningitis that can be run on demand, and to make the test easy enough to operate that most hospital laboratories can offer it on an immediate basis in order to provide maximum medical impact.

METHODS

A sensitive and specific test on the GeneXpert was developed for detection of enteroviral RNA in cerebrospinal fluid. The automated test was carried out in a disposable GeneXpert cartridge, which conducts the steps of nucleic acid purification, amplification and detection of enteroviral genomic RNA in ∼ 2 h. Preclinical and clinical studies showed sensitivities of 97.1 and 98%, respectively, and specificities of 100 and 97.1%, respectively. In February 2006, the test received FDA clearance as an aid in the diagnosis of viral meningitis.

CONCLUSIONS

Rapid and accurate molecular diagnostic testing for enterovirus infection provides clinicians with information they need to make the best patient decisions in managing patients with meningitis. The GeneXpert enterovirus assay features on-demand availability and a level of simplicity that allows nearly any hospital laboratory to offer a sophisticated test that was once the exclusive domain of reference laboratories.

External quality assessment for enterovirus 71 and coxsackievirus A16 detection by reverse transcription-PCR using armored RNA as a virus surrogate

Three armored RNAs (virus-like particles [VLPs]) containing target sequences from enterovirus 71 (EV71) and coxsackievirus A16 (CA16) and a pan-enterovirus (pan-EV) sequence were constructed and used in an external quality assessment (EQA) to determine the performance of laboratories in the detection of EV71 and CA16. The EQA panel, which consisted of 20 samples, including 14 positive samples with different concentrations of EV and either EV71 or CA16 armored RNAs, 2 samples with all 3 armored RNAs, and 4 negative-control samples (NaN(3)-preserved minimal essential medium [MEM] without VLPs), was distributed to 54 laboratories that perform molecular diagnosis of hand, foot, and mouth disease (HFMD) virus infections. A total of 41 data sets from 41 participants were returned; 5 (12.2%) were generated using conventional in-house reverse transcription-PCR (RT-PCR) assays, and 36 (87.8%) were generated using commercial real-time RT-PCR assays. Performance assessments of laboratories differed; 12 (29.3%) showed a need for improvement. Surprisingly, 4 laboratories were unable to detect EV71 RNA in any samples, even those containing the highest concentration of 10(7) IU/ml. Furthermore, the detection sensitivity for EV71 among all laboratories (82.1%) was substantially lower than that for EV (97.4%) or CA16 (95.1%). Overall, the results of the present study indicate that EQA should be performed periodically to help laboratories monitor their ability to detect HFMD viruses and to improve the comparability of results from different laboratories.

Development of a highly sensitive real-time one step RT-PCR combined complementary locked primer technology and conjugated minor groove binder probe

Background

Enterovirus (EV) infections are commonly associated with encephalitis and meningitis. Detection of enteroviral RNA in clinical specimens has been demonstrated to improve the management of patients, by ruling out other causes of disease.

Method

To develop a sensitive and reliable assay for routine laboratory diagnosis, we developed a real-time one step reverse transcription polymerase chain reaction (RT-PCR) assay with minor groove binder probes and primers modified with complementary locked primer technology (TMC-PCR). We checked the sensitivity of the developed assay by comparing it to a previously published TaqMan probe real-time one-step RT-PCR (TTN-PCR) procedure using enteroviral isolates, Enterovirus Proficiency panels from Quality Control on Molecular Diagnostics (QCMD-2007), and clinical specimens from patients with suspected EV infections.

Results

One hundred clinical specimens from 158 suspected viral meningitis cases were determined to be positive by the TMC-PCR assay (63.29%), whereas only 60 were found to be positive by the TTN-PCR assay (37.97%). The positive and negative agreements between the TMC-PCR and TTN-PCR assays were 100% and 59.2%, respectively.

Conclusion

This data suggest that the TMC-PCR assay may be suitable for routine diagnostic screening from patient suspected EV infection.

A comparative analysis of routine techniques: Reverse transcriptase polymerase chain reaction (RT-PCR) and five cell lines for detection of enteroviruses in stool specimens

BACKGROUND AND OBJECTIVES

Each year, Enteroviruses infect millions of people and cause different diseases. The agents are usually detected using cell culture. RD (Rhabdomyosarcoma) and L20B (L cells) are among the recommended cells by the World Health Organisation (WHO) for this purpose. Even though cell culture is the most common method used in diagnosing Enteroviruses in stool specimens, this particular method poses some problems, which include false positive or negative results, lack of a unique cell line for diagnosing all Enterovirus types in addition to being time consuming. For these reasons, an attempt was made to find better techniques of Enterovirus detection. RT-PCR (Reverse Transcriptase Polymerase Chain Reaction) is a technique used in place of the cell culture method. In this study, the cell culture method was compared with RT-PCR for detection of Enteroviruses in stool specimens.

MATERIAL AND METHOD

First, the chloroform treated stool samples were inoculated onto five cell lines, including RD, L20B, Hep-2 (Human Epidermoid carcinoma cell line), Vero (Verde Reno) and GMK (Green Monkey Kidney). The results were then compared with data from Enterovirus detection using the RT-PCR technique.

RESULTS AND CONCLUSION

The difference between RT-PCR and cell culture results was significant. Enteroviruses were detected in 24% of specimens using RT-PCR while cell lines could isolate Enteroviruses in just 14.4% of the samples.

Outbreak of Neurologic Enterovirus Type 71 Disease: A Diagnostic Challenge

BACKGROUND

Similar to poliovirus, enterovirus type 71 (EV71) causes severe disease, including aseptic meningitis, encephalitis, acute flaccid paralysis, and acute cardiopulmonary dysfunction. Large epidemics of EV71 infection have been reported worldwide.

METHODS

After recognition of a cluster of cases of EV71 disease, we reviewed records of patients with EV71 disease who required hospitalization at The Children's Hospital in Denver, Colorado, from 2003 through 2005. The presence of enterovirus was detected by reverse-transcriptase polymerase chain reaction (PCR) and/or viral culture of specimens from multiple sources, and the virus was typed as EV71 using genetic sequencing.

RESULTS

Eight cases of EV71 disease were identified in both 2003 and 2005. Fifty-six percent of patients with EV71 disease were < or = 6 months of age (range, 4 weeks to 9 years). All 16 patients had EV71 central nervous system infection. Enterovirus PCR (EV-PCR) of cerebrospinal fluid specimens yielded positive results for only 5 (31.2%) of the 16 patients; all of these patients were < 4 months of age and had less severe disease. However, EV-PCR of upper respiratory tract specimens yielded positive results for 8 (100%) of 8 patients, and EV-PCR of lower gastrointestinal tract specimens yielded positive results for 7 (87.5%) of 8 patients.

CONCLUSIONS

An outbreak of neurologic EV71 disease occurred in Denver, Colorado, during 2003 and 2005. Likely, EV71 disease remains unrecognized in other parts of the United States, because EV-PCR of cerebrospinal fluid frequently yields negative results. EV-PCR of specimens from the respiratory and gastrointestinal tracts had higher diagnostic yields than did EV-PCR of cerebrospinal fluid. EV71 infection should be considered in young children presenting with aseptic meningitis, encephalitis, acute flaccid paralysis, or acute cardiopulmonary collapse. EV71 infection may be an underrecognized emerging disease in the United States.

Comparison of cell culture with RT-PCR for enterovirus detection in stool specimens from patients with acute flaccid paralysis

Since October 2000, Iran has been declared polio-free by the World Health Organization (WHO). Despite the fact that poliomyelitis caused by polioviruses has been eliminated from Iran, the number of acute flaccid paralysis (AFP) cases has not been reduced. Therefore, it is of great importance to investigate the other viral agents that may cause AFP (mainly nonpolio enteroviruses, which play a significant role in the etiology of neurological syndromes). Some enteroviruses do not grow in the conventional cell lines that are being used for enterovirus detection. Furthermore, the virus titer is an important factor in the sensitivity of cell culture to detect the virus. The fact that cell culture is a time-consuming procedure is another reason to find a more practical method for enterovirus detection. Therefore, a more sensitive and rapid method should be used to detect enteroviruses as efficiently as possible in the stool specimens of AFP cases. The aim of this study was to evaluate cell culture and RT-PCR in enterovirus detection. Findings have shown that RT-PCR can increase the rate of nonpolio enterovirus detection by up to 10% in comparison with cell culture. Also, the rapid detection of enteroviruses by RT-PCR can decrease both the unnecessary use of antibiotics and the costs in clinical practice. For this reason, we find that RT-PCR is a more practical technique for enterovirus detection.

Detection of enteroviruses by reverse-transcriptase polymerase chain reaction in cell culture negative stool specimens of patients with acute flaccid paralysis

The aim of this study was the detection of a 114 base pairs amplicon in 5' non-translated region of enterovirus genome in stool specimens of patients with acute flaccid paralysis (AFP) which were negative on cell culture. One hundred and twenty stool specimens were collected from AFP cases and tested with cell culture (RD, L20B and Hep2 cell lines). RT-PCR was carried out for the specimens with negative cell culture result. A 10% raise in enterovirus detection was observed with RT-PCR. This increased sensitivity can improve the detection of enterovirus serotypes which grow poorly in cell culture, and can thus alter significantly the medical care of patients with acute flaccid paralysis.

Multicenter beta trial of the GeneXpert enterovirus assay

The GeneXpert Dx system (Cepheid, Sunnyvale, CA) is a fully integrated and automated nucleic acid sample preparation, amplification, and real-time detection system. It consists of an instrument, a personal computer, and disposable fluidic cartridges. The analytical sensitivity and specificity of the GeneXpert enterovirus assay (GXEA) were determined with a panel of 63 different enterovirus serotypes and 24 other microorganisms, respectively. The potential for blood, hemoglobin, white blood cells, and excess protein to interfere with the assay was also assessed. The performance parameters of the GXEA were determined at three sites with 102 cerebrospinal fluid (CSF) samples obtained from patients with suspected meningitis. All samples were tested for enterovirus RNA with locally developed reverse transcription-PCR (RT-PCR) assays at the trial sites and with a seminested RT-PCR and an analyte-specific reagent (Cepheid) at a reference laboratory. The 5' nontranslated region was the target for all of the PCR assays except the seminested RT-PCR, which amplified a VP1 sequence. The VP1 amplicon was sequenced to identify the enterovirus types. Consensus reference laboratory RT-PCR results were used to classify cases of enteroviral meningitis. The GXEA detected all of the enterovirus serotypes and none of the other microorganisms tested except rhinovirus 16. The assay was unaffected by moderate amounts of blood or blood components. Thirty-six (35%) of the CSF samples tested had at least one positive PCR result. Eleven different enterovirus serotypes were identified in the positive samples. The GXEA had a sensitivity of 97.1% (95% confidence interval [CI], 84.7 to 99.9%) and a specificity of 100% (95% CI, 94.6 to 100%) for the diagnosis of enteroviral meningitis.

Quantitative PCR-enhanced immunoassay for measurement of enteroviral immunoglobulin M antibody and diagnosis of aseptic meningitis

A PCR-enhanced immunoassay (PIA) to detect enterovirus (EV) immunoglobulin M (IgM) for diagnosis of recent EV infection was recently developed. This test was compared with another EV IgM capture technique, the solid-phase reverse immunosorbent test (SPRIST). Fourteen of 43 serum samples from aseptic meningitis patients were positive by PIA, whereas 10 were positive by SPRIST. One of 39 control serum samples was weakly positive by PIA. A single-serum-dilution real-time PCR-based PIA for EV IgM (quantitative PIA [QPIA]) was also developed and evaluated against PIA, SPRIST, an EV IgM radioimmunoassay (RIA), and clinical data. A mixture of 12 EVs was used as the antigen. Results from investigating four groups of serum samples were as follows. (i) The nine PIA-positive serum samples in group 1 were all positive by QPIA. (ii) Group 2 consisted of 59 serum samples from aseptic meningitis patients. Nineteen of 30 serum samples (63%) taken at hospital admission were positive by QPIA. Of these, 17 were positive in EV PCR. (iii) None of the 30 control serum samples in group 3 were positive by QPIA. (iv) For the 24 serum samples in group 4, of which 11 were positive and 13 were negative by RIA, the QPIA results were completely concordant. The sensitivity and specificity of QPIA for diagnosis of EV infection were 70 and 80%, respectively. QPIA provides a rational strategy for the detection of EV IgM, allows the use of viral antigens with minimal purification, and needs no virus-specific reagents apart from those in the PCR. QPIA is a generally applicable method for the detection of viral IgM in IgM capture assays.

Highly sensitive assay for detection of enterovirus in clinical specimens by reverse transcription-PCR with an armored RNA internal control

The objective of the present study was the development of a diagnostic reverse transcription (RT)-PCR for the specific detection of enterovirus (EV) RNA in clinical specimens controlled by an internal control (IC) RNA. The IC RNA contains the same primer binding sites as EV RNA but has a different probe region. The IC RNA was packaged into an MS2 phage core particle (armored) and was added to the clinical sample to allow monitoring of both extraction efficiency and RT-PCR efficiency. Serial dilutions of the IC RNA were made, and the detection limit of the RT-PCR was tested in a background of EV RNA-negative cerebrospinal fluid. The sensitivity and specificity of the RT-PCR assay were tested by using all 64 known EV serotypes, several non-EV serotypes, and two Quality Control for Molecular Diagnostics (QCMD) Program EV proficiency panels from 2001 and 2002. In total, 322 clinical specimens were tested by RT-PCR, and to establish the clinical utility of the RT-PCR, a comparison of the results of viral culture and RT-PCR was done with 87 clinical specimens. The lower limit of sensitivity was reached at about 150 copies of IC RNA/ml. All 64 EV serotypes were positive, while all non-EV serotypes were negative. All culture-positive samples of the 2001 QCMD proficiency panel (according to the 50% tissue culture infective doses per milliliter) were positive by RT-PCR. Invalid results, i.e., negativity for both EV RNA and IC RNA, due to inhibition of RT-PCR were observed for 33.3% of the members of the 2002 QCMD proficiency panel and 3.1% of the clinical specimens. Inhibition of RT-PCR could be relieved by the addition of 400 ng of bovine alpha-casein per microl to both the RT reaction mixture and the PCR mixture. With this optimized protocol, the results for all samples of the 2002 QCMD proficiency panel and all clinical specimens except one fecal sample (0.3%) were valid. Evaluation of the clinical samples demonstrated that EV infection could be detected in 12 of 87 samples (13.8%) by RT-PCR, while viral culture was negative. Our data show that the RT-PCR with armored IC RNA offers a very reliable and rapid diagnostic tool for the detection of EV in clinical specimens and that the addition of bovine alpha-casein relieved inhibition of the RT-PCR for 99.7% of clinical specimens.

Molecular diagnosis of viral infections of the central nervous system

The development of techniques for the amplification of DNA and RNA opened the way for the creation of extremely specific, sensitive, and rapid diagnostic tests for the detection of viral infections of the central nervous system. Polymerase chain reaction (PCR) and reverse transcription PCR diagnostic assays have revolutionized the approach to the diagnosis of important viral pathogens--in particular, enteroviruses (EVs), herpes viruses, and JC virus (JCV). These molecular approaches to diagnosis have led to improvements in clinical outcome and patient care. Additionally, their use has permitted a better understanding of the natural history and clinical spectrum of the syndromes caused by these important human pathogens. This article summarizes the current understanding with regard to the available, molecularly based, diagnostic assays for the detection of EVs, herpes viruses, and JCV.

Evaluation of real-time PCR versus PCR with liquid-phase hybridization for detection of enterovirus RNA in cerebrospinal fluid

A LightCycler and two TaqMan real-time PCR assays were evaluated against an older PCR with liquid-phase hybridization method for the detection of enterovirus RNA in 74 patient samples. The two-step LightCycler and the two-step TaqMan formats correlated well with each other (r(2) = 0.90) and were equally sensitive compared to the liquid-phase hybridization method, whereas the one-step recombinant Tth DNA polymerase format was rather insensitive, detecting enterovirus RNA in only about one-half of those patient samples previously positive by liquid-phase hybridization. The two-step TaqMan method was optimized utilizing 10 micro l of cDNA and demonstrated the highest degree of analytical sensitivity among the methods evaluated in our study, being able to reproducibly quantify down to 510 copies of enteroviral RNA/ml of cerebrospinal fluid. This new assay can be performed in 4 h, is much less labor intensive, and showed less cross-reactivity with rhinovirus than the liquid-phase hybridization assay. Thus, the two-step TaqMan assay should prove useful in the diagnosis of enteroviral meningitis versus bacterial meningitis, thereby resulting in timely and appropriate clinical management that can amount to significant cost savings to the patient and health care system.

Rapid detection of enterovirus infection by automated RNA extraction and real-time fluorescence PCR

BACKGROUND

Molecular detection has been shown to be superior to tissue culture for the detection of enteroviruses in cerebrospinal fluid (CSF) specimens.

OBJECTIVES

In this study, a qualitative molecular assay based on automated RNA extraction with the MagNA Pure LC and real-time PCR on the LightCycler (LC) instrument was evaluated and compared with an in-house molecular assay.

STUDY DESIGN

A total of 109 CSF specimens were investigated for the comparative study. The detection limit of the new molecular assay was determined with 10-fold dilutions of two enterovirus strains and with the Third European Union Concerted Action Enterovirus Proficiency Panel.

RESULTS

With the enterovirus strains, the detection limit of the LC assay was found to be 0.1 TCID(50) (50% tissue culture infective dose). When samples of the Third European Union Concerted Action Enterovirus Proficiency Panel were tested, both molecular assays gave identical results to the expected results, which were based upon the results of three reference laboratories using a total of four different molecular methods before distribution of the panel. When clinical specimens were tested, there was a correlation between the LC assay and the in-house assay in 105 of 109 cerebrospinal fluids.

CONCLUSIONS

The new molecular assay allows rapid detection of enterovirus RNA in CSF. It was found to be labor saving and showed sufficient sensitivity.

Evaluation of a one-tube RT-PCR system for detection of enteroviruses

BACKGROUND

A highly sensitive PCR assay for early and rapid detection of enteroviral (EV) RNA in CSF is necessary to investigate the role of EV in acute neurological illnesses.

OBJECTIVES

To evaluate and compare two PCR protocols (Titan one-tube RT-PCR and random primed RT-PCR) for detection of enteroviral RNA in CSF.

STUDY DESIGN

The PCR protocols were evaluated for lower limit of input detection using log dilutions of five stock EV strains and an isolate of enterovirus-71 in minimum essential medium and three EV stock strains in CSF. The tests were also applied on 77 CSF samples, 46 from patients with suspected acute EV neurological illness and 31 from 'disease controls'.

RESULTS

Even though in the initial virus titration assays there was no statistically significant difference in the limit of input detection by Titan system and the random primed two-step PCR, the latter had a higher positivity rate when used on CSF samples from patients (20/46 vs. 10/46, P<0.01).

CONCLUSIONS

Random primed RT-PCR assay is superior to Titan one-tube RT-PCR for detection of EV RNA in CSF.

Evaluation of the roche AMPLICOR enterovirus PCR assay in the diagnosis of enteroviral central nervous system infections

BACKGROUND

Enteroviruses cause a substantial number of cases of aseptic meningitis annually in the USA. While culture has been useful in the detection of patients with viral meningitis it is time-consuming and lacks sensitivity. Detection of viral nucleic acid in patient specimens has been demonstrated to improve enteroviral detection.

OBJECTIVES

A research use only commercial amplification assay, the Roche AMPLICOR EV test, was compared to culture for the diagnosis of enteroviral meningoencephalitis.

STUDY DESIGN

Four-hundred and sixty-five consecutive CSF samples sent prospectively for suspicion of enteroviral infection were evaluated by PCR and shell-vial culture. Clinical information and CSF analysis were used to resolve PCR positive, culture negative samples. Sensitivity and specificity were calculated using resolved data.

RESULTS

There were 138 samples which met the definition of a true positive. Of these culture detected 77 (sensitivity 55.8%) and PCR detected 136 (sensitivity 98.6%). PCR missed two culture positive samples. Upon repeat testing, these CSF samples were found to contain inhibitors.

CONCLUSIONS

The Roche AMPLICOR EV-PCR test was statistically more sensitive than culture (P<0.001) in the detection of enteroviruses in CSF in patients suspected of having enteroviral meningitis. This assay also has the advantage of a rapid turnaround time of 5-6 h compared to 3-5 days for culture.

A one-step RT-PCR assay using an enzyme-linked detection system for the diagnosis of enterovirus meningitis

BACKGROUND

Enteroviruses are the most common cause of meningitis in the United States, with an estimated 50000-75000 cases each year. Enteroviral meningitis (EVM) is frequently a diagnosis of exclusion, as viral cultures lack sensitivity and require prolonged incubation periods.

OBJECTIVE

To develop a sensitive and rapid test for the diagnosis of EVM.

STUDY DESIGN

A rapid, one-step, reverse transcriptase-polymerase chain reaction (RT-PCR) was used in a prospective analysis of 160 patients who had cerebrospinal fluid (CSF) tested for enterovirus.

RESULTS

Of the 160 patients, 14 were excluded due to missing CSF viral culture data. A total of 14 were CSF culture positive (10 with pleocytosis) and 19 were PCR positive (15 with pleocytosis). The ability to detect enterovirus by either culture or PCR correlated significantly with the white blood cell count in the CSF (P=0.001). Based on a clinical definition of enterovirus culture positive and pleocylosis: ten had definite EVM and 12 had probable EVM (pleocytosis without any other cause). Four had possible EVM (CSF culture positive without pleocytosis) and 18 had pleocytosis due to other causes. PCR was positive in all ten patients with definite EVM. Five out of 12 patients with probable EVM and three out of four patients with possible EVM. No patients with pleocytosis due to other causes were PCR positive and one patient that was defined as EVM negative (culture negative and no pleocytosis) was PCR positive. Overall, PCR was positive in 18 out of the 26 patients with a likelihood of EVM, while CSF culture was positive in only 14 cases. Our results demonstrated that RT-PCR enhances the sensitivity of enterovirus detection in CSF (69 vs. 54% for culture).

CONCLUSION

The diagnosis of EVM is difficult to make clinically: the enhanced sensitivity and rapid turn around time of PCR will be of great clinical benefit.

Reverse-transcription polymerase chain reaction detection of the enteroviruses

OBJECTIVE

This review focuses on commercial and in-house-developed reverse-transcription polymerase chain reaction (RT-PCR) assays used for the detection of enteroviral infections. In addition to providing details on the performance of RT-PCR, its specificity, and sensitivity, the clinical utility of this diagnostic method with specific reference to its impact on hospitalization and cost savings is addressed.

DATA SOURCES

MEDLINE was searched for reports relating to RT-PCR detection of the enteroviruses in adults and children. The search was restricted to studies reported in English language journals.

STUDY SELECTION

Reports documenting detailed information regarding the RT-PCR conditions, primers, sensitivity, specificity and, if relevant, clinical impact were selected for analysis.

DATA EXTRACTION

Details regarding method of extraction of the enteroviral genome, the primers used, RT-PCR conditions, and sensitivity and specificity of the assay were extracted from the literature. For reports detailing the use of RT-PCR in the clinical management of enteroviral infections in children, the reduction in duration of hospitalization and health care cost savings were recorded.

DATA SYNTHESIS

Reverse-transcription PCR can increase the yield of detection of enteroviruses from cerebrospinal fluid by a mean of approximately 20% over tissue culture. Reverse-transcription PCR of cerebrospinal fluid has been shown to exhibit sensitivity and specificity values of 86% to 100% and 92% to 100%, respectively. Reductions of 1 to 3 days of hospitalization per patient are predicted if RT-PCR is used to diagnose enteroviral meningitis in children.

CONCLUSIONS

Reverse-transcription PCR detection of enteroviral infections is an extremely rapid, sensitive, and specific diagnostic modality. Both commercial assays and assays developed in-house appear to be equivalent with regard to sensitivity and specificity. Reverse-transcription PCR diagnosis of enteroviral infections in children could reduce the length of hospitalization and result in significant health care cost savings.

Amplicor enterovirus polymerase chain reaction in patients with aseptic meningitis: a sensitive test limited by amplification inhibitors

OBJECTIVE

To evaluate the sensitivity and specificity of reverse-transcription polymerase chain reaction (RT-PCR) and routine cell culture for the detection of enterovirus in cerebrospinal fluid.

METHODS

Thirty-eight cerebrospinal fluid specimens were included. Cell culture was inoculated immediately and incubated for 14 days. An aliquot was kept frozen for Amplicor RT-PCR. Chart review was performed to determine the validity of the results.

RESULTS

Nine of 38 specimens were positive for enterovirus by culture, and 14 were positive by RT-PCR. There were 7 discrepancies between the 2 methods. Six specimens were positive by RT-PCR and negative by the culture method. The 1 culture-positive but RT-PCR--negative specimen was determined to contain PCR inhibitors. All discrepant results were confirmed as true positives by chart review. Patients whose cerebrospinal fluid was negative by both methods had a final diagnosis other than enterovirus infection.

CONCLUSION

Amplicor PCR is more sensitive than cell culture (93.3% vs. 60%) and is very specific. With the incorporation of appropriate controls for the detection of amplification inhibitors, RT-PCR could be a valuable tool in the diagnosis of enteroviral meningitis.

Clinical utility of polymerase chain reaction testing for enteroviral meningitis

BACKGROUND

During summer enteroviral meningitis is a common cause of febrile illness in children, who are typically hospitalized for 2 to 3 days if bacterial infection is suspected. It has been hypothesized that a sensitive polymerase chain reaction (PCR) assay could quickly confirm the diagnosis and subsequently decrease hospitalization costs. However, to have maximum impact results should be available within 24 h. This necessitates daily assays on small numbers of samples.

METHODS

We examined the clinical utility of a PCR assay during two summers, comparing length of stay and charges. Only during the second summer were results reported to clinicians. Case controls were patients with negative PCR assay results but uncomplicated, presumed viral infections. We determined the cost per case identified with and without pleocytosis as a screen for PCR testing.

RESULTS

During the first summer 25% (5/20) of patients with positive PCR assay results remained hospitalized for >2 days. During the second summer 10.2% (6 of 59) of children with positive enteroviral PCR assay results but 37.9% (25 of 66) of case controls remained hospitalized for >2 days. The mean length of hospitalization was significantly (P < 0.05) shorter for patients with positive PCR test results than for case controls. The material cost was approximately $238 per case identified.

CONCLUSIONS

PCR testing has clinical utility for diagnosis of enteroviral meningitis. Although the demands for daily testing make the test expensive, it appears to be cost-effective with savings related to shorter hospital stays.

Multicenter quality assessment of PCR methods for detection of enteroviruses

We conducted a multicenter evaluation of commercial and in-house PCR methods for the detection of enteroviruses. Three coded panels of test and control RNA samples, artificial clinical specimens, and representative enterovirus serotypes were used to assess amplification methods, RNA extraction methods, and reactivities with different enterovirus serotypes. Despite several differences between PCR methods, there was good agreement, although some variation in sensitivity was observed. Most PCR methods were able to detect enterovirus RNA derived from 0.01 50% tissue culture infective dose (TCID50) and were able to detect at least 1 TCID50 of enterovirus in cerebrospinal fluid, stool, or throat swab specimens. Most were also able to detect a wide range of enterovirus serotypes, although serotypic identification was not possible. Some laboratories experienced false-positive results due to PCR contamination, which appeared to result mainly from cross-contamination of specimens during RNA extraction. Provided that this problem is overcome, these PCR methods will prove to be a sensitive and rapid alternative to cell culture for the diagnosis of enterovirus infection.

Detection by PCR of enteroviruses in cerebrospinal fluid during a summer outbreak of aseptic meningitis in Switzerland

Enteroviruses (EV) are among the most common causes of aseptic meningitis. Standard diagnostic techniques are often too slow and lack sensitivity to be of clinical relevance. EV RNA can be detected within 5 h by a commercially available reverse transcription-PCR (RT-PCR) test kit. Cerebrospinal fluid (CSF) samples from 68 patients presenting with aseptic meningitis during a summer outbreak in Switzerland were examined in parallel with cell culture and commercial RT-PCR. RT-PCR was positive in all 16 CSF specimens positive by cell culture (100%). In addition, 42 of 52 (80%) CSF samples negative by cell culture were PCR positive. In 26 of these 42 (62%) patients, viral culture from other sites (throat swab or stool) was also positive. The CSF virus culture took 3 to 7 days to become positive. Echovirus 30 was the type most often isolated in this outbreak. The sensitivity of CSF RT-PCR based on clinical diagnosis during this aseptic meningitis outbreak in patients with negative bacterial culture results was 85%, i.e., considerably higher than the sensitivity of CSF virus culture (24%). We conclude that this commercial RT-PCR assay allows a positive diagnosis with minimal delay and may thus influence clinical decisions.