key: cord-0923787-zstpi8de
authors: Ng, Deborah H L; Choy, Chiaw Yee; Chan, Yi-Hao; Young, Barnaby E; Fong, Siew-Wai; Ng, Lisa F P; Renia, Laurent; Lye, David C; Chia, Po Ying
title: Fever Patterns, Cytokine Profiles and Outcomes in Covid-19
date: 2020-08-24
journal: Open Forum Infect Dis
DOI: 10.1093/ofid/ofaa375
sha: 97467ac9727b1d597fae4ffbd4e85bc295f6c924
doc_id: 923787
cord_uid: zstpi8de

BACKGROUND: Prolonged fever is associated with adverse outcomes in dengue viral infection. Similar fever patterns are observed in COVID-19 with unclear significance. METHODS: We conducted a hospital-based case-control study of patients admitted for COVID-19 with prolonged fever (fever>7 days) and saddleback fever (recurrence of fever, lasting less than 24 hours, after defervescence beyond day 7 of illness). Fever was defined as a temperature of ≥60.0oC. Cytokines were determined with multiplex microbead-based immunoassay for a subgroup of patients. Adverse outcomes were hypoxia, intensive care unit (ICU) admission, mechanical ventilation and mortality. RESULTS: A total of 142 patients were included in the study. 12.7% (18/142) of cases had prolonged fever and 9.9% (14/142) had saddleback fever. Those with prolonged fever had a median duration of fever for 10 days (IQR 9–11 days) for prolonged fever cases, while fever recurred at a median of 10 days (IQR 8–12 days) for those with saddleback fever. Both prolonged (27.8% vs 0.9%, p <0.01) and saddleback fever (14.3% vs 0.9%, p= 0.03) were associated with hypoxia compared to controls. Cases with prolonged fever were also more likely to require ICU admission compared to controls (11.1% vs 0.9%) (p=0.05). Patients with prolonged fever had higher IP-10 and lower IL-1α levels compared to those with saddleback fever at the early acute phase of disease. CONCLUSION: Prolonged fever beyond 7 days from onset of illness can identify patients who may be at risk of adverse outcomes from COVID-19. Patients with saddleback fever appeared to have good outcomes regardless of the fever.

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Since its first report in Wuhan, China in December 2019, COVID-19 has rapidly spread, becoming a pandemic with more than 3 million confirmed cases [1] . Singapore reported its first imported case of COVID-19 in a traveller from Wuhan on 23 January 2020, followed by its first locally transmitted case on 7 Feb 2020[2, 3] .

COVID-19 generally presents as an acute respiratory illness, with fever, fatigue and dry cough being commonly reported symptoms [4] [5] [6] . In particular, fever was reported in about 72 -98.6% of patients, usually lasting less than 7 days [4, [7] [8] [9] [10] . However, there was a proportion of patients from our hospital who displayed two patterns of fever: one group had fever persisting into the second

week of illness, while the second group displayed a saddleback pattern of fever, similar to that previously observed in dengue [11] . While it has been reported that complications of COVID-19 occur in the second week of illness, the significance of these two patterns of fever with regards to the development of complications is unknown [4] . A dysregulated immune response in has been postulated to lead a deleterious cytokine storm [12] . In addition, the contribution of immunosenescence towards the establishment of cytokine storm and severe illness can be seen in previous studies [5] . In this study, we aim to examine the characteristics of patients who developed these patterns of fever and their correlation to cytokine levels, as well as association with adverse outcomes in A c c e p t e d M a n u s c r i p t

We conducted a case-control study of patients who were admitted to the National Centre for Infectious Diseases (NCID), with a positive SARS-CoV-2 polymerase chain reaction (PCR) assay, from 23 January to 31 March 2020. Upon admission, all patients will have a chest X-ray (CXR), admission full blood count (FBC), renal and liver panel, C-reactive protein (CRP) and lactate dehydrogenase (LDH), and nasopharyngeal swab for SARS-CoV-2 PCR. Patients who test positive were not discharged until they have two negative PCR tests 24 hours apart [13] .

Demographic and comorbidity data, symptoms and signs, vital signs, laboratory and radiology results were obtained from electronic medical records. A standardised template was used for recording daily signs and symptoms, vital signs and management. The reference values for the normal ranges of laboratory tests were in accordance with those used by the hospital laboratory.

Repeat laboratory investigations and CXR were done for those with prolonged or saddleback fever and collected. For cases with prolonged fever, investigations were repeated beyond day 7 of illness, and for cases with saddleback fever, investigations were repeated at point of fever recurrence.

Additional microbiological investigations such as blood and urine cultures, influenza and respiratory viral multiplex PCR, dengue NS1 and serology, were ordered at the discretion of the primary treating clinician. The results of these microbiological investigations were also collected and analysed.

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Fever was defined as a temperature of 38.0°C or higher. Duration of fever was calculated from the date of first symptom onset to the date of defervescence (defined as temperature less than 37.5°C

for at least 24 hours) during the hospital admission. Cases with prolonged fever were defined as patients with fever lasting more than 7 days. Cases with saddleback fever were defined as patients with recurrence of fever lasting less than 24 hours, after defervescence, beyond day 7 of illness.

Cases without prolonged or saddleback fever were included as controls. Cases who already on supplemental oxygen or were already in the ICU at the time of satisfying criteria for prolonged or saddleback fever were excluded from the analysis. Hypoxia was defined as requirement for supplemental oxygen. Outcomes of interest were hypoxia, admission to intensive care unit (ICU), need for mechanical ventilation and mortality. was applied to ascertain significant differences in the immune mediator levels between the patients experiencing different fever patterns. Statistical analyses were performed using GraphPad Prism version 8. A p value of <0.05 was taken to be statistically significant.

Approval for data collection by retrospective chart review with a waiver of written informed consent from study participants, was granted by the Singapore Ministry of Health under the Infectious Diseases Act as part of the outbreak investigation [14] . A c c e p t e d M a n u s c r i p t

We screened 170 patients who were admitted to NCID from 23 January to 31 March 2020, of which 24 were excluded from our study as they did not have complete data. Another four patients were excluded from the primary analysis as they had a saddleback pattern of fever that lasted more than 24 hours. 12.7% (18/142) of cases had prolonged fever and another 9.9% (14/142) had saddleback fever. Data were collected for the remaining 110 patients from this cohort as controls. 57.0%

(81/142) of all study subjects were male, and median age was 42 years (IQR 31 -54 years).

Demographics were similar across the three groups (Table 1) . 7.0% (10/142) of patients had comorbidities, such as diabetes (n=4), ischemic heart disease (n=3) and asthma (n=3).

Cases with prolonged fever had a median duration of fever lasting 10 days (IQR: 9 -12 days). Higher heart rate, respiratory rate and lower oxygen saturation (spO2), systolic and diastolic blood pressure (BP) were associated with prolonged fever compared to controls (Table 1) . Prolonged fever was also associated with lower platelet count and higher CRP compared to controls. On repeat testing, prolonged fever was associated with drop in hemoglobin, and a rise in CRP and LDH. (Table 2) For cases with saddleback fever, fever recurred at a median of 10 days after symptom onset (IQR: 8 -12 days). Higher respiratory rate, lower SpO2, lower systolic BP were also associated with saddleback fever compared with the control group. However, there were no significant differences in the admission laboratory values between the control and saddleback fever group. There were no significant changes in laboratory findings when repeated at the point of fever, except for a rise in platelet and lymphocyte counts (Table 2) .

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To our knowledge, this is the first study to examine the association between the patterns of fever and outcomes in COVID-19. While both prolonged and saddleback fever showed an association with hypoxia, only prolonged fever was associated with ICU admission. This corresponded with a rise in CRP and LDH seen in cases with prolonged fever, which are known to be associated with adverse prognostic factors in COVID-19 [15, 16] . In contrast, cases with saddleback fever showed no significant change upon repeating their laboratory tests. Despite the progression on CXR in over onethird of cases with saddleback fever, these cases tend to do well. This suggest that in patients with prolonged fever, close monitoring for deterioration should be instituted, while patients with saddleback fever who remain well and do not require supplemental oxygenation are unlikely to require close monitoring in hospital. In addition, as these patients with saddleback fever tend to do well, there is also no need for repeat laboratory testing or CXR, as the results are unlikely to change management or clinical outcomes.

None of the three patients who entered ICU had culture-proven nosocomial infections, suggesting that the fevers observed in ICU were likely related to COVID-19 infection. Nevertheless, as patients in ICU are at higher risk of nosocomial infections, due diligence should be done to exclude other causes of fever [17] . Physicians may consider stopping antimicrobials if all investigations are unyielding and patients remain hemodynamically stable. However, as the number of patients with prolonged fever requiring ICU admission is small in this cohort, further studies should be done to prove this correlation.

The differences in cytokine and chemokine profiles amongst control patients with fever ≤ 7 days, patients with prolonged fever or patients with saddleback fever at the early acute phase of illness A c c e p t e d M a n u s c r i p t suggest that different immunological responses could result in the differences in the clinical phenotype observed. Although there were no significant differences in the white blood cell counts, absolute values of lymphocytes and CRP, we found significant differences in plasma IL-6 and IP-10 levels between the prolonged fever and control patients. In addition to their pro-inflammatory properties, both IL-6 and IP-10 have been reported to be associated with disease severity and ICU admission in COVID-19 [18] [19] [20] . In addition, IP-10 has also been reported to be associated with increased viral load, lung injury, ICU admission and mortality [21] . This corroborated well with our findings of increased hypoxia cases in patients with prolonged fever.

Interestingly, there are also higher plasma levels of IL-1RA in patients with prolonged fever compared to control patients. Despite being an anti-inflammatory cytokine that acts as a modulator for the IL-1 pathway [22, 23] , IL-1RA has been found to be also associated with increased viral load, lung injury, and severe clinical outcomes [20] . IL-1RA is naturally secreted by human host to limit activity of IL-1 during hyperinflammation [22] . The elevation of circulating IL-1RA may reflect overactive IL-1 activation that has been reported to associated with severe outcome in COVID-19 [24] .

In patients with saddleback fever, higher levels of IL-1⍺, IL-21, IL-22 and SDF-1⍺ were observed compared to control patients. IL-1⍺ is a pyrogenic cytokine that plays a central role in inflammatory diseases like arthralgia [23] . The higher levels of IL-1⍺ could have initiated the first occurrence of fever, while pro-inflammatory cytokines IL-21 and IL-22 mediate the activation of T cells and M1 macrophages [25, 26] , which drive the recurrence of fever in the saddleback fever cases. Comparing the difference between prolonged fever cases and saddleback fever cases, we found an increased level of IL-1⍺ level and lower IP-10 level on admission. A lower IP-10 level is consistent with the finding that saddleback fever cases tend to have better clinical outcomes than prolonged A c c e p t e d M a n u s c r i p t fever cases. This phenomenon is also observed in other viral fevers, like dengue virus [27] and thrombocytopenia syndrome virus [28, 29] , where patients with more severe illness had higher serum levels of IP-10. However, it is interesting that there are higher pro-inflammatory IL-1⍺ levels in patients with saddleback fever. IL-1 is dual function cytokine that can act as both a transcription factor and as a damage-associated molecular pattern (DAMP), which can be released by necrotic cells to promote and exacerbate inflammation via IL-1R1 [30] . In hypoxic conditions, it can trigger the expression of chemokines that attract neutrophils and monocytes to the ischemic tissue [31] .

Importantly, the upregulation of IL-1 pathway on monocytes can increase prostaglandin E2 expression and drive fever [32] . Notably, in a study of three COVID-19 patients, peak IL-1⍺ appears to precede the nadir of lung function [33] , and may herald worsening inflammation. This apparent difference in IL-1⍺ between prolonged fever cases and saddleback fever cases may have occurred due to dynamic immune response and timepoint of sample collection. Patients with prolonged fever may have had higher levels of IL-1⍺ earlier on prior to sample collection.

The results of this study can be used to optimize placement of patients with COVID-19. Home or community isolation facilities and the other iterations for positive cases are commonly used globally to isolate positive patients [34, 35] . Such facilities free up hospital beds to enable sicker patients to be optimally managed. Teleconferencing is often used to monitor these cases for potential deterioration. Self-recorded temperature monitoring for COVID-19 patients on home or community isolation facilities can be used to triage patients who need admission to hospital. In addition, in comparison to other parameters such as respiratory rate, heart rate or blood pressure, fever is easy to detect and readily identifiable as a risk factor for severe disease. Based on this study, patients with saddleback fever who remain well can be monitored in the community, while patients who have fever for more than seven days should be admitted for closer monitoring.

One limitation of the study is the small sample size of our cohort. A larger sample size may help to identify if prolonged and saddleback fever could be used as predictors for adverse outcomes such as A c c e p t e d M a n u s c r i p t ICU admission, mechanical ventilation or death. Our cohort only had one mortality, and this may be reflective of the overall low mortality rate in Singapore. At the time of writing, the mortality rate from COVID-19 in Singapore was 0.09% [36] . Another limitation of our study is that onset of fever dependant on self-reporting by patients. Over-or under-reporting of the onset of fever prior to admission could affect the number of patients found to have prolonged or saddleback fever. We also excluded four patients whose fever pattern did not fulfill the case definition for prolonged or saddleback fever. Given that two of them were admitted to ICU, this may suggest another phenotype of patients who are at higher risk of adverse outcomes. A larger cohort might help to improve our understanding of these patients.

In conclusion, we reported on prevalence, risk factors, cytokine profiles and outcomes of patients with COVID-19 who had saddleback or prolonged fever. Patients with prolonged fever are more likely to develop hypoxia and have a more pronounced inflammatory response in comparison to those in the saddleback fever group, which is also reflected in the different cytokine profiles between the two groups. The different prognosis for these two groups of patients have implications on the distribution of increasingly burdened hospital resources given the exponential rise in cases worldwide. More studies are required to validate the findings of this report. M a n u s c r i p t Tables   Table 1 

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The authors declare no competing conflict of interest.A c c e p t e d M a n u s c r i p t A c c e p t e d M a n u s c r i p t M a n u s c r i p t