Biomedical Engineering Reference
In-Depth Information
15
Molecular Diagnosis of Severe Acute Respiratory
Syndrome
Enders K. O. Ng and Y. M. Dennis Lo
Summary
The etiologic agent of severe acute respiratory syndrome (SARS) has been identified
as a new type of coronavirus, known as SARS-coronavirus (SARS-CoV). Although the
SARS epidemic has subsided, many authorities, including the World Health Organiza-
tion (WHO) and the Centers for Disease Control and Prevention (CDC), have warned of
the possible re-emergence of this highly infectious disease. Although antibody-based
diagnosis of SARS has been demonstrated to be a reliable proof of SARS infection, it is
not sensitive enough for detection during the early phase of the disease. To date, based
on the publicly released full genomic sequences of SARS-CoV, various molecular
detection methods based on reverse-transcription polymerase chain reaction (RT-PCR)
have been developed. Although most of the assays have initially been focused on RNA
extracted from nasopharyngeal aspirates, urine, and stools, several of the more recently
developed assays have been based on the analysis of RNA extracted from plasma and
serum. Such assays allow the more standardized quantitative expression of viral loads
and are potentially useful for early SARS diagnosis. In this chapter, two real-time quan-
titative RT-PCR systems for the quantification of SARS-CoV RNA in serum are dis-
cussed. The two RT-PCR systems, one aimed toward the nucleocapsid region and the
other toward the polymerase region of the virus genome, have a detection rate of up to
80% during the first week of illness. These quantitative systems are potentially useful
for the early diagnosis of SARS and can also provide viral load information that might
assist clinicians in making a prognostic evaluation of an infected individual.
Key Words:
Serum RNA; SARS-CoV RNA; viral RNA extraction; RNA quantifica-
tion; real-time quantitative reverse-transcription PCR.
1. Introduction
The identification of severe acute respiratory syndrome-coronavirus (SARS-
CoV) as the etiologic agent of SARS has led scientists to develop rapid and
sensitive diagnostic tests
(
1-6
)
. Although the SARS epidemic has subsided,
