Keywords
COVID-19, Dynamics, SARS-CoV-2, Coronavirus, PCR.
This article is included in the Emerging Diseases and Outbreaks gateway.
This article is included in the Coronavirus collection.
COVID-19, Dynamics, SARS-CoV-2, Coronavirus, PCR.
In December 2019, multiple cases of undiagnosed pneumonia emerged in China. Sequencing on respiratory samples indicated the presence of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) causing Coronavirus Disease 2019 (COVID-19).1–3
The main method of diagnosing COVID-19 is by the isolation of SARS-CoV-2 through Reverse Transcriptase Polymerase Chain Reaction (RT-PCR or PCR) nucleic amplification testing of respiratory samples.4 In a study done by Yu et al. the viral load predicted by the Cycle threshold (Ct) value was higher in sputum samples than nasopharyngeal and throat swabs. Patients who had an increasing viral load and lower CT values had a progressive disease and more severe lung injury.5,6 Furthermore patients with higher initial viral loads had worse outcomes and more prolonged viral shedding.7 The viral dynamics studied in 18 different patients resembled that of patients with influenza rather than SARS-CoV.8
Given the importance for early identification of patients with severe disease and that a low Ct value is proposed to be inversely proportional to disease severity,7 we aim to describe the different clinical manifestations and disease severities in relation to the initial and subsequent Ct values in patients who were admitted to King Faisal Specialist Hospital and Research Centre-Riyadh (KFSH&RC).
A retrospective, single center observational study was undertaken and included all patients who were admitted to KFSH&RC-Riyadh in one month in 2020 and had a confirmed diagnosis of COVID-19 based on a positive PCR taken from a respiratory sample. The study was approved by the policies and guidelines for clinical research at KFSH&RC and the KFSH&RC-Riyadh Institutional Review Board (IRB) (RAC # 2201054). As this is a retrospective study, consent to participate from patients was waived by the IRB.
All but two patients were followed for a total duration of 14 days after the initial diagnosis. Repeat PCR results were sought during data abstraction for days 3, 7, 10 and 14. The Ct value was identified on the obtained samples. All patients were treated according to KFSH&RC treatment guidelines (as detailed below).
Epidemiological, demographic, clinical, laboratory, treatment administered, and outcome of the disease data were obtained from the patient’s electronic medical records. All data were entered in a password-protected database developed using the Research Electronic Data Capture (REDCap) version 9.4 software. The Ct values on admission and follow-up samples were obtained from the microbiology laboratory. As hydroxychloroquine (HCQ) and azithromycin (AZI) were one of the commonly used regimens for treatment, we divided our cohort into HCQ/AZI and non-HCQ/AZI treated groups.
Sample: Combined nasopharyngeal and throat swabs were collected from patients.
COVID-19 RNA extraction method: RNA was extracted utilizing Qiagen QIAamp® DSP Viral RNA Mini Kit or QIAamp® Viral RNA Mini Kit EZ1 following the manufacturer recommendations, utilizing 200 μL of sample and eluted with 60 μL of buffer.
RNA amplification and detection: RealStar ® SARS-CoV-2 RT-PCR Kit RUO Altona was used for RNA detection and differentiation of lineage B-betacoronavirus (β-CoV) and SARS-CoV-2 specific RNA. Reagent system included an internal control and positive control for both targets, B-βCoV and SARS-CoV-2 following manufacturer recommendations. Tests were done on Rotor-Gene ® Q. Tests were reported as positive and negative accordingly. Each test was run into cycles and up to 45 cycles, and the Ct value was recorded according to the cycle for which the test became positive.
All patients admitted were treated according to hospital guidelines that had been revised and edited according to emerging evidence. Up to the time of writing, the hospital had issued six versions of COVID-19 treatment and management guidelines, the initial three versions were released at the time of data collection and analysis. The first guideline was issued on March 5th, 2020 followed by the second and third versions that were released on March 19th and 26th, 2020 respectively.
At first (and as per the Ministry of Health guidelines for Saudi Arabia), all patients who were eligible to be treated in KFSH& RC-Riyadh and who had a positive COVID-19 PCR were admitted to the hospital regardless of the presence or absence of symptoms.
All admitted patients had baseline lab tests requested including Complete Blood Count with Differential (CBCD), urea and electrolytes, creatinine, C-Reactive Protein (CRP), Liver Function Test (LFT), blood glucose, and ferritin level. Electrocardiograms (ECGs) were also conducted to look at the corrected QT interval prior to starting medications.
Multiplex PCR using the QIAstat-Dx Respiratory SARS-CoV-2 Panel is intended for the detection and differentiation of nucleic acid from SARS-CoV-2 and multiple other respiratory viruses and atypical bacteria. In addition, if Middle East Respiratory Syndrome Coronavirus (MERS-CoV) is needed, a BIOFIRE® RP2.1plus is used which detects SARS-CoV-2, MERS-CoV and other common respiratory pathogens and atypical bacteria.
In the latest revision, further investigations were added as the available literature suggested their correlation with disease severity and outcome. These included erythrocyte sedimentation rate (ESR), D-Dimer, Creatinine Kinase (CK), troponin, Lactate Dehydrogenase (LD) and haptoglobin. All patients had a baseline chest X-Ray, and those with an abnormal finding or those at high risk underwent Computed Tomography (CT) scan of the chest.
In the earliest guidelines issued, patients were divided according to the presence or absence of symptoms, and radiological evidence of pneumonia. Severity was indicated by the need for Intensive Care Unit (ICU) admission. Following the latest guideline, patients were categorized into four categories (asymptomatic, mild, moderate and severe infection) (Table 1).
In the first guidelines, active treatment was given for patients with radiological evidence of pneumonia. Those patients were treated as community acquired pneumonia in addition to Lopinavir/Ritonavir +/- Ribavirin. Other treatment options were decided after discussion with an infectious disease (ID) physician. As the evidence evolved and as the roles of HCQ and AZI were thought to lead to favorable outcomes, hospital guidelines changed to include HCQ and AZI for all patients presenting with symptoms regardless of symptoms severity and presence or absence of pneumonia. The HCQ regimen involved a loading dose of 400 mg oral twice daily in the first day, followed by 200 mg orally every 12 hours for a duration of 6 days. AZI was given at a dose of 500 mg daily for 3 days. Lopinavir/Ritonavir were used if the above regimen was contraindicated. In the latest guidelines, Tocilizumab was added as a possible treatment for cytokine release syndrome. Its use was strictly prescribed by an ID physician and for patients who were admitted to the ICU with evidence of cytokine storm and elevated Interleukin (IL) 6. The recommended dose was 4-8 mg/kg and repeated after 12 hours if the response for the 1st dose was poor and to a maximum of two doses.
In this study, a confirmed case is defined as a patient with at least one positive PCR test for COVID-19. Cure is defined as a single negative COVID-19 PCR test. Persistent disease is defined as a positive PCR on day 14 following the initial positive test or sometime afterwards. A high risk patient is any patient who is positive for COVID-19 and has any of the following comorbidities: Age above 60 years, lung disease, cancer, cardiovascular or cerebrovascular disease, renal or liver disease, diabetes, hypertension, immunocompromising conditions (Human Immunodeficiency Virus (HIV), post solid organ or hematopoietic stem cell transplant, on active chemotherapy or receiving an immunomodulator or immunosuppressant therapy), or pregnancy.
Data were entered in an electronic database system – REDCap version 9.4. Over 300 data items were abstracted from the medical records for each included patient. JMP/SAS software (version 15.0) and Cytel (StatXact version 6.0 and LogXact version 6.0) were used for data analysis. Data were summarized using mean (+/− standard deviation) or median (with interquartile range) for continuous data. Categorical data were summarized using frequencies and percentages. All analysis methods are available and could be reproduced with R, a freely available software platform.
Patients were divided into two groups - a group receiving a hydroxychloroquine-based regimen and the second group receiving a regimen not including hydroxychloroquine. The Ct values were compared between the two groups and correlated with disease severity and outcome with a Spearman’s correlation coefficient. Cure, persistent disease and death were the three main outcome categories. Comparisons between the two treatment groups were evaluated with nonparametric methods (Wilcoxon Rank Sum Test) given the small numbers and inability to evaluate distributional requirements. Time-to-event analyses were also carried out with the Kaplan-Meier technique.
During the study time period, 35 subjects had presented to the KFSH&RC-Riyadh and for whom sufficient follow-up information was available (21 women and 14 men). In total, 28 patients were considered at presentation mild (stage B), 5 were moderate (stage C), and 2 were asymptomatic (stage A). The average age was 49.9±21.9 years. Comorbidities were observed in 68.6% of the cases. All patients had tested positive for SARS-CoV-2 by PCR. Table 2 shows the disease severity progression through the course of 14 days following admission. Table 3 presents symptoms that developed sometime during the course of infection.
Clinical severity | Admission | Day 3 | Day 7 | Day 10 | Day 14* |
---|---|---|---|---|---|
No disease | 0 | 0 | 0 | 2 | 7 |
Asymptomatic (Stage A) | 2 | 2 | 7 | 13 | 14 |
Mild (Stage B) | 28 | 21 | 14 | 8 | 6 |
Moderate (Stage C) | 5 | 11 | 10 | 8 | 1 |
Severe (Stage D) | 0 | 1 | 4 | 3 | 3 |
Dead | 0 | 0 | 0 | 1 | 2 |
There were nine different treatment profiles administered across the 35 subjects when considering the seven different drugs used during the course of illness – HCQ, AZI, Kaletra, Ribavirin, Tocilizumab, IVIG, and other. Of interest is to differentially identify from among the 35 study subjects those who were given the combination of HCQ and AZI as their initial treatment from those who were not given this combination as their initial treatment. The schematic in Figure 1 depicts the course of treatments received by each of the 35 subjects and how it was decided into which of the two treatment groups each was assigned post-hoc. It is seen that 21 (60%) pateints were given HCQ and AZI as their initial treatment. Henceforth, this treatment group will be referred to as the HCQ/AZI group. Those subjects not in the HCQ/AZI treatment group will be denoted the group.
Table 4 displays a comparison of baseline characteristics between the two treatment groups. There was no significant difference in age and gender between the two groups. The frequency of individuals with a past history of smoking in the group was significantly less in the group. No differences were observed in the radiological findings or vital signs between the two groups. Among the baseline laboratory values, ALT was lower in the group. Table 5 displays a comparison of the baseline clinical severity of the two treatment groups; there is no statistically significant difference in the two.
Asymptomatic (Stage A) | Mild (Stage B) | Moderate (Stage C) | Severe (Stage D) | Total | |
---|---|---|---|---|---|
n (%) | |||||
2 (14.29) | 11 (78.57) | 1 (7.14) | 0 (0.00) | 14 | |
0 (0.00) | 17 (80.95) | 4 (19.05) | 0 (0.00) | 21 | |
Total | 2 | 28 | 5 | 0 | 35 |
Table 6 shows a comparison for the number of days to reach negative RT-PCR results between the two treatment groups. From the table it can be seen that 7 of the 21 -treated subjects remained positive for 14 days after admission whereas 12 were able to reach a negative status within that time period. There were 2 subjects not fully followed for 14 days post-admission for whom a conclusion could not be reached. Moreover, 9 of the 14 -treated subjects remained positive for 14 days after admission, whereas 5 were able to reach a negative status within that time period. Considered as two ordered multinomial distributions, the two columns did not show a statistically significant difference between the two treatment groups (p = 0.1571) with respect to the time to reach negativity. Figure 2 presents a time-to-negativity actuarial chart for the two treatment groups with no statistically significant difference in the two curves.
Days to reach negative | ||
---|---|---|
7 | 3 | 1 |
10 | 4 | 1 |
14 | 5 | 3 |
Never | 7 | 9 |
Unclear* | 2 | 0 |
Total | 21 | 14 |
The Ct values ranged from a minimum of 11.44 to a maximum of 38.35 across the 5 time points (days 0, 3, 7, 10, and 14), across the two treatment groups, and during the 14 days. There were many days among the 35 subjects for which Ct values were not available (i.e. a PCR test was not carried out). These missing results presented a challenge in trying to evaluate the relative Ct profiles between the two treatment groups. It was noted however that, although the Ct value was missing, a positivity/negativity indication was often present in the medical record when the Ct value was missing. Among those missing both the Ct value and an indication of positivity/negativity, a clinical severity stage value (A, B, C, D, or dead) was present for each of the 5 days. Using this information together with whatever Ct values were present, an attempt at imputing information for missing Ct values was made using the following logic. The logic lead to an ordinal Ct score 1, 2, 3, or 4 for each subject for each of the 5 days (0, 3, 7, 10, and 14), and it will be referred to as the Ct score. The methodology includes the following five steps:
Note that, even though a Ct value of 40 or more was not seen among the 35 subjects, this category was conceptualized to accommodate a Ct value for a subject who reached a negative RT-PCR test or a status of no disease.
2. For each day when a subject’s Ct value was available, a score (as described in #1 above) was assigned to the Ct score.
3. It was noted that a Ct value was present (i.e. not missing) on day 0 for all 35 subjects. It was therefore the case that a true Ct based score was able to be assigned to each subject’s day 0.
4. For all but 8 of the subjects, at least one Ct value was available at one of the follow-up days (3, 7, 10, or 14). In those situations, a linearly interpolated (assuming the 5 days 0, 3, 7, 10, and 14 as equidistant) score was assigned. Reassuringly, for every interpolation, the value was consistent with the associated clinical severity stage.
5. In addition to the 8 subjects for whom no Ct values subsequent to day 0 were available, there were 16 subjects who had a subsequent Ct value but were missing day 14, i.e. for which interpolation was not possible based on an endpoint Ct value (two boundary endpoints being required in order to interpolate). That is, there were 24 subjects for whom it was necessary to rely on the positivity/negativity result or the clinical severity stage in order to impute a Ct score. The following was inferred:
• For 12 subjects, a score of 4 could be assigned as on the days subsequent to their last Ct value, they were recorded as being RT-PCR negative;
• For 3 subjects, a score of 1 could be assigned as they either died or they were at stage D;
• For 5 subjects, a score of 4 could be assigned to day 14 as a result of a negative RT-PCR, and intermediate interpolations were then made (e.g. scores of 2 or 3 as appropriate);
• For 2 subjects, there was no information on positivity/negativity on the days when the Ct value was missing, but the clinical severity stage strongly suggested the score (scores of 2 and 3 were imputed);
• For 2 subjects both treated with , too little information was available, and an inference could not be made, and they were not included in this analysis.
In the end, as a result of the above, a complete Ct score profile was available for 33 of the 35 subjects. A breakdown of these profiles separately for the two treatment groups is as shown in Tables 7 and 8. In reviewing the tables, it can be seen that there are 12 unique Ct score profiles for those treated with , and 14 unique Ct score profiles for those treatment with . It was found that 5 of the profiles from Table 7 were the same as 5 of the profiles from Table 8, i.e. 18 unique profiles of Ct scores across all subjects. The 18 profiles are presented in Table 9 and ranked in order of favorability, where a more favorable outcome is one for which a higher score is reached earlier. A rank of 1 is the least favorable profile and larger ranks assigned to a profile indicate a more favorable one. A rank-based comparison was performed on these two sets of the ranks, and the results suggested no statistically significant difference in the two treatment groups (HCQ/AZI median rank: 11; median rank: 5.5; p = 0.2212 (Kruskal-Wallis)) with respect to the time to a recovering Ct value.
Profile | Day 0 | Day 3 | Day 7 | Day 10 | Day 14 | N |
---|---|---|---|---|---|---|
A1 | 1 | 1 | 1 | 1 | 3 | 1 |
A2 | 2 | 2 | 2 | 2 | 2 | 2 |
A3 | 2 | 2 | 2 | 3 | 4 | 1 |
A4 | 1 | 1 | 2 | 2 | 2 | 1 |
A5 | 3 | 3 | 2 | 3 | 4 | 1 |
A6 | 3 | 3 | 4 | 4 | 4 | 1 |
A7 | 1 | 1 | 2 | 2 | 4 | 1 |
A8 | 1 | 2 | 2 | 2 | 2 | 2 |
A9 | 1 | 2 | 2 | 3 | 3 | 1 |
A10 | 1 | 1 | 1 | 2 | 2 | 1 |
A11 | 2 | 2 | 3 | 4 | 4 | 1 |
A12 | 1 | 1 | 1 | 1 | 1 | 1 |
Profile | Day 0 | Day 3 | Day 7 | Day 10 | Day 14 | N |
---|---|---|---|---|---|---|
B1 | 1 | 2 | 2 | 2 | 2 | 1 |
B2 | 1 | 2 | 2 | 2 | 4 | 3 |
B3 | 2 | 3 | 3 | 4 | 4 | 1 |
B4 | 2 | 3 | 4 | 4 | 4 | 2 |
B5 | 2 | 2 | 3 | 4 | 4 | 1 |
B6 | 1 | 2 | 3 | 4 | 4 | 1 |
B7 | 1 | 1 | 1 | 2 | 4 | 1 |
B8 | 1 | 1 | 1 | 1 | 1 | 2 |
B9 | 2 | 1 | 1 | 2 | 3 | 1 |
B10 | 3 | 3 | 2 | 3 | 4 | 1 |
B11 | 3 | 3 | 4 | 4 | 4 | 1 |
B12 | 2 | 2 | 3 | 2 | 2 | 2 |
B13 | 2 | 2 | 2 | 4 | 4 | 1 |
B14 | 3 | 1 | 2 | 2 | 2 | 1 |
Table 10 describes the change in disease severity from admission to day 14. One patient was classified at admission with stage A and then his disease developed at day 14 to stage D. Around 36% of the patients presented with mild (stage B) severity and then lessened to asymptomatic (stage A). In total, 7 patients presented with mild stage then they were tested negative by day 14. Table 11 provides an overall comparison of the clinical severity on day 14 between the two treatment groups with no statistically significant difference between the two (p > 0.05).
Several lab tests were carried out on the study subjects during admission (Table 12). These included hemoglobin, creatinine, D-dimer, CD4, IgG, and others. From among the lab tests the following were found to significantly relate to disease severity at admission: D-dimer, troponin, LD, C4, absolute CD8 (p < 0.05).
The current study involves subjects presenting early in the COVID-19 pandemic and much knowledge about the virus and the ensuing disease has been generated since the time of these subjects’ presentations. However, there is still relatively little new knowledge related to the time profile of Ct values and their potential value in understanding the course of disease. This study aims to add some related insights and particularly how treatment efficacy (here a comparison of HCQ and AZI) may be able to be evaluated based on Ct values. Additionally, the study recognizes the challenges associated with timely RT-PCR testing and always documenting the Ct values and proposes an imputation method that may be used with conservative statistical assumptions for analyses of Ct profiles. There are several limitations of this study. It is a retrospective study that has a small sample size and was conducted in a single center.
In this study, a treatment regimen of HCQ and AZI was identified for 21 of 35 subjects testing positive for SARS-Cov2 and admitted to a single tertiary care hospital early in the COVID-19 pandemic.
This study presents the follow-up information gathered on the patients for up to 14 days after admission, specifically days 0 (admission), 3, 7 10, and 14. Of particular interest for the follow-up was the clinical staging of COVID-19 and the Ct value from the RT-PCR. Ct values were scored as 1, 2, 3, or 4 based on the value of the Ct being below 20, 20-30, 30-40, or 40 or more. The follow-up Ct value was not consistently available at each of the four follow-up timepoints following admission, and imputation of missing Ct scores (1-4) was made using an algorithm based on coincident clinical stage and interpolation. Recognizing the assumptions associated with the designed imputation scheme, a conservative, nonparametric (i.e. rank-based) method was used for comparing the two treatment groups with respect to outcomes. A validation study of this method is going to follow.
The patients treated with the HCQ and AZI were similar to those not treated with respect to all demographic, clinical, radiological, and laboratory features with the exception of a higher rate of smoking history among those treated with HCQ and AZI. The follow-up profiles of the two groups were compared with respect to improvement trends (i.e. improving clinical staging and improving Ct scores). There was no evidence of any difference in the sets of profiles for the two treatment groups.
Dryad: SARS-CoV-2 Viral dynamics, https://doi.org/10.5061/dryad.15dv41nwm.9
Data are available under the terms of the Creative Commons Zero “No rights reserved” data waiver (CC0 1.0 Public domain dedication).
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Is the work clearly and accurately presented and does it cite the current literature?
Yes
Is the study design appropriate and is the work technically sound?
No
Are sufficient details of methods and analysis provided to allow replication by others?
No
If applicable, is the statistical analysis and its interpretation appropriate?
No
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Are the conclusions drawn adequately supported by the results?
No
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: SARS-CoV-2
Alongside their report, reviewers assign a status to the article:
Invited Reviewers | |
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Version 1 11 Aug 22 |
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