Volume 10, Number 2—February 2004
THEME ISSUE
2004 SARS Edition
Laboratory Study
Real-Time Reverse Transcription–Polymerase Chain Reaction Assay for SARS-associated Coronavirus
Table 3
Efficiency of real-time PCR assaysa
Mean CTb values at estimated RNA transcript copy number | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|
SARS1 |
7.5 x 100 |
7.5 x 101 |
7.5 x 102 |
7.5 x 103 |
7.5 x 104 |
7.5 x 105 |
7.5 x 106 |
Slopec |
Efficiency (%)d |
|
RNA transcript alone |
Neg |
38.65±1.48 |
34.25±0.57 |
31.1±0.14 |
27.5 |
24.2 |
20.55±0.07 |
–3.55 |
91.1 |
|
RNA transcript + extracte |
Neg |
38.05±0.92 |
34.85±0.21 |
31.55±0.07 |
27.75±0.07 |
24.4 |
20.6 |
–3.49 |
93.3 |
|
SARS2 |
2 x 100 |
2 x 101 |
2 x 102 |
2 x 103 |
2 x 104 |
2 x 105 |
2 x 106 |
|||
RNA transcript alone |
35.4±0.57 |
32.1±0.14 |
29.45±0.64 |
26.15±0.07 |
22.9±0.14 |
19.4 |
16.35±0.07 |
–3.21 |
104.9 |
|
RNA transcript + extract |
Neg |
34.55±1.91 |
29.2±0.28 |
26.2 |
23.1 |
19.6±0.14 |
16.6 |
–3.48 |
93.9 |
|
SARS3 |
||||||||||
RNA transcript alone |
39.3 |
36.2±0.42 |
32.8 |
29.1±0.14 |
25.9 |
22.15±0.07 |
19.2 |
–3.39 |
97.1 |
|
RNA transcript + extract | 40.3 | 36.2±0.28 | 33.4±0.28 | 29.9±0.21 | 26.05±0.07 | 22.55±0.21 | 19.65±0.21 | –3.42 | 96.1 |
aPCR, polymerase chain reaction; CT, threshold cycle number.
bValues shown are mean of triplicate samples ± standard deviations.
cSlope determined from the formula: Y = Y intercept – slope log10. Slopes calculated for SARS1 (7.5 x 106 to 7.5 x 101); SARS2 (2 x 106 to 2 x 101); SARS3 (2 x 106 to 2 x 100).
dEfficiency = [10(–1/slope)] – 1.
eReactions performed in presence of pooled total nucleic acid extract from 20 human respiratory specimens.