What are the diagnostic challenges in #Covid_19 disease? The diagnosis seems to be dependent on the quality of the testing method, the type of the sample, the clinical picture and the course of the disease. This is a rough review of the literature as of March 29th. 1/
Could a variable positivity rate of RT-PCR kits mirror our experience with MERS-CoV? In this study bit.ly/33V6A1x of 336 MERS patients, 89% had a positive result after 1 swab, 96.5% after 2 consecutive swabs, and 97.6% after 3 consecutive swabs. 2/
This paper bit.ly/2UOSn1I suggests that samples from lower resp. tract have a higher positivity rate for #Covid_19 than from upper resp. tract. Clinical information regarding symptoms and disease course are missing, and the number of some types of samples was small. 3/
In this paper bit.ly/2wNluul, among 30 pairs of throat swab and sputum samples, viral loads of #SARS_COV_2 were significantly correlated between the two sample types for days 1–3 (R²=0·50, p=0·022), days 4–7 (R²=0·93, p<0·001), and days 7–14 (R²=0·95, p=0·028). 4/
In this paper bit.ly/2QRd0JK, sputum seems to have a more prolonged viral shedding for #SARS_COV_2 (18 days) than nasopharyngeal swabs (12 days). 5/
This paper bit.ly/3asqEuh suggests that patients with risk factors should not be excluded from #Covid_19 despite that viral RNA is not detected in the upper resp. samples. Most of the samples though were collected after antiviral treatment. 6/
This paper bit.ly/2QX6eSK shows that RT-PCR is sensitive and reliable for #Covid_19, but ddPCR performed better in detecting low-viral load samples.The article suggests that sputum can be a better indicator of viral replication in the body than throat and nasal swabs. 7/
In this paper bit.ly/3anWSXI a pooling approach for the standard RT-qPCR test for #Covid_19, suggests that a single positive sample can be detected even in pools of up to 32 samples, with an estimated false-negative rate of 10%. 8/
In this study bit.ly/33SFw2R out of 1014 #Covid_19 patients, 59% had positive RT-PCR and 88% had positive CT scans; using RT-PCR as a reference, the sensitivity of chest CT imaging was 97%. However clinical and laboratory data were limited. 9/
In this paper bit.ly/33T7Py5 the sensitivity of chest CT was greater than that of RT-PCR (98% vs 71%, respectively, p<.001). That may be though due to variations in the accuracy of nucleic acid detection methods, low initial viral load or improper clinical sampling. 10/
In this study bit.ly/2WOsfa1 of 167 #Covid_19 patients, concordant CT scan and PCR test results were observed in 93% of patients, and discordant results were observed in 4% (positive PCR but negative CT scan) and in 3% (negative initial PCR and positive CT scan). 11/
This paper bit.ly/3aq6bXi highlights that both RT-PCR and chest CT should be considered as the key determinants for the diagnosis and management of #Covid_19 patients. 12/
In this paper bit.ly/3bwTwSr antibody test aided to confirm 4 patients with #Covid_19 from 52 suspects who failed to be confirmed by RT-PCR and 7 patients from 148 close contacts with negative RT-PCR. 13/
This paper bit.ly/33SGn3z shows that the positive detection rate for #Covid_19 is significantly increased (98.6%) when combined IgM ELISA assay with PCR for each patient compared with a single qPCR test (51.9%). 14/
In this paper bit.ly/3bxlHRc in 173 #Covid_19 patients, presence of antibodies was <40% in first 7 days & then rapidly increased to 100%, 94%, & 80% for IgM, & IgG by 15th. day. In contrast, viral RNA decreased from 67% before day 7 to 46% in days 15-39. 15/
This paper bit.ly/2UqjLUJ, shows that the viral load of #SARS_COV_2 on posterior oropharyngeal saliva-samples of 23 patients, was high at presentation and declined steadily. Viral RNA could be detected for 20 days or longer in 1/3 of patients who survived. 16/
The ELISA assays for #SARS_COV_2 in this paper bit.ly/3asjyGp by Florian Krammer et al seem to be so sensitive that they can detect the virus as early as 3 days post symptom onset. 17/
This paper bit.ly/3dxp0d3 suggests that ELISA has a high sensitivity, especially for the detection in serum samples from #Covid_19 patients after 10 days of post-disease onset. 18/
Here finddx.org/covid-19/pipel… is a not comprehensive list of #SARS_COV_2 tests commercially available or in development for the diagnosis of #Covid_19. The information is directly submitted by suppliers or obtained from public sources, and is not independently verified. 19/
