Table 1.
Studies on RT-PCR research assays
| Date, author, sample size | Time of collection from onset/hospitalization | Genes, Samples, Statistical Parameters/performance | Limitations |
|---|---|---|---|
| 01/23/20, Corman et al, 310 samples20 | N/A | Genes: E and RdRp, Specificity 100%. | Primers for RNA identical to 2019- nCoV target sequence & lack of testing with SARS-CoV-2. |
| 02/12/20 To et al, 12 patients31 | Median 2 days from hospitalization (range 0–7 days). | Sensitivity: 11/12 (91.7%). Specificity: 33/33 (100%) |
Easier sampling. Limitations include limited sample size. |
| 02/19/20, Fang et al, 51 patients34 | 3 ± 3 days for both chest CT and RT-PCR. | Sensitivities: Chest CT (50/51, 98%) Initial RT-PCR (36/51, 71%). |
Study limited by lack of information on laboratory procedure and positive controls |
| 02/26/20, Ai et al, 1014 patients33 | Median interval between chest CT and initial RT-PCR was 1 day (range 0–7 days). | 21/601 RT-PCR positive & not chest CT. 308/413 had positive chest CT & negative RT-PCR. 59% positive rate of RT-PCR. Chest CT sensitivity = 97%, specificity = 25%, accuracy = 68%, PPV = 65%, NPV = 83%. | |
| 03/04/20, Chan et al, 273 specimens25 | 0–18 days - respiratory specimens, 4–15 days for other specimens. | Sensitivity: 85% with samples from respiratory tract, 11.1% from non-respiratory tract. | Primers had 7–9 nucleotide differences with SARS-CoV |
| 03/05/20, Konrad et al, 669 respiratory samples21 | Not reported. | SARS-CoV E gene assay was more sensitive than the two RdRp gene assays; however, the E gene assay showed unspecified signals at late cycles. | Lack of information on procedure and positive controls. |
| 03/05/20, Pfefferle et al, 88 samples22 | N/A | Specificity: 88/88 (100%) Sensitivity: LOD of 275.72 copies/process at 95% detection probability |
Unable to validate the performance of the assay using clinical SARS-CoV-2 positive samples |
| 03/07/20, Liu et al, 4880 patients30 | Not reported. | Sensitivities and specificities not reported.. | Validity of test results was not assessed. |
| 03/11/20, Wang et al, 1070 specimens32 | Pharyngeal swabs on 1–3 days after hospitalization. Variable time for other specimens. | Sensitivities: BAL (14/15; 93%), sputum (75/104; 72%), nasal (5/8; 63%), bronchoscope brush biopsy (6/13; 46%), pharyngeal (126/398; 32%), feces (44/153; 29%), blood (3/307; 1%), urine (0/72, 0%). | Insufficient data to analyze correlation between symptoms or disease course and test results. Small sample size for some specimen types. |
| 03/25/20, Long et al, 204 patients35 | Study group = 2.6 ± 1.7 days, control group = 3.2 ± 1.6 days. | Sensitivities: Chest CT (35/36, 97.2%), initial RT-PCR (30/36, 83.3%). | RT-PCR only performed in patients with fever due to limited test kit supplies. Small sample size. |
| 03/26/20, Li et al. 610 patients36 | Initial RT-PCR done prior to admission. Repeated 1–2 days if negative or weakly positive. | Not reported | Study limited by lack of detailed patient information or RT-PCR protocol. |
| 03/30/20, CDC, 2071 respiratory specimens28 | Not reported. | Specificity: 60/60 for both assays. 49/2071 respiratory specimens tested positive. |
Study limited by positive controls. |
| 04/08/20, Nalla et al. 300 specimens27 | Not reported. | 100% specific. Sensitivity: CDC N2 and Corman E-gene: 10/10 and able to reliably detect samples with only 6 genomic equivalents of viral RNA. | Limited sample size |
| 04/09/20, Xiao et al. 70 patients37 | Symptoms to nucleic acid conversion, median (IQR): Consecutive false-negative patients = 36 (28–40), all other patients = 21 (18–26). | 15/70 (21.4%) positive on RT-PCR after two consecutive negative results. | Study does not mention details about the commercial detection kit. |
Abbreviations: RT- PCR – reverse transcriptase polymerase chain reaction, RNA – ribonucleic acid, CDC – Centers for Diseases Control and Prevention, LOD – Limit of detection, CT-computed tomography, COVID – coronavirus disease, N-nucleocapsid, RdRp – RNA dependent RNA polymerase, E- envelope, BAL – broncho-alveolar lavage, SARS-CoV-2 - severe acute respiratory syndrome conronavirus-2, N/A – Not available.