Molecular Diagnostic Tests


NAATs for detection of SARS-CoV-2 RNA 

See the table below for comparison of the four molecular tests offered by our lab.  Abbott IDNOW is a POCT test available in the EDs, selected clinics and ORs.  Cepheid Xpress is deployed in peds after hours clinics and selected other outpatient location as POCTs and also in our Micro Lab.  This test is currently orderable in EPIC by all providers and provides the most rapid results of all tests offered in lab. 
 
You may have questions about alternative specimen types if NP or Mid-turbinate swab collection is not possible due to trauma to the nose or bleeding issues. The next best alternate would be an OP swab.  We no longer accept saliva.
 
We do not routinely report the Ct/Cn values provided by the Cepheid and Abbott m2000 and Alinity m tests.  There has been growing interest in the possibility of using reverse transcriptase polymerase chain reaction (RT-PCR) cycle threshold (Ct) values as a surrogate measure of the amount of SARS-CoV-2 in clinical specimens. Ct value-based estimates of viral density have been used to predict progression to severe COVID-19 disease, infer transmissibility and differentiate active viral replication from prolonged virus shedding. However, definitive data to support the predictive value of Ct values in these situations are lacking. Ct values generated by qualitative PCR assays do not reliably correspond to specific RNA concentrations and are not consistent across platforms. In addition, multiple factors other than viral load are known to affect Ct values. Therefore, we does do not routinely include Ct values in laboratory reports, opting instead to share them on a case-by-case basis. 

 

SARS-CoV-2 Molecular Tests

Characteristic
Abbott IDNOW
Cepheid Xpress
Abbott m2000/Alinity m
Hologic Panther
Technique
Isothermal NEAR amplification
Real-time PCR
Real-time PCR
Transcription- mediated amplification
Detects 
SARS-CoV-2
Multiplex test including SARS-CoV-2, INF A and B, and RSV
SARS-CoV-2
SARS-CoV-2
Point(s) of service
POCT 
POCT and in lab (Micro)
In lab (Mol Path)
In lab (Mol Path
Analysis time
5 to 15 min
25-36 min (POCT);  2 h (in lab)
6 h (Alinity m) to 8 h (m2000) 
8 h
Specimen
Dry nasal swab (provided)
NP or mid-turbinate swabs in 3ml UTM or saline
NP or mid-turbinate swabs in 3ml UTM or saline
NP or mid-turbinate swabs in 3ml UTM or saline
EPIC lab number
POC 309
POC 311
LAB 8994
LAB 8572
LAB 8572
Intended use
Symptomatic individuals
Symptomatic and asymptomatic individuals
Symptomatic and asymptomatic individuals
Symptomatic and asymptomatic individuals
Limit of detection copies/ml
500
250
100
100
Sensitivity
94.4%
97.8%
100%
100%
Specificity
99.3%
95.6%
96.5%
98.2%

 

 

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