Impact of Fever Thresholds in Detection of COVID-19 in Department of Veterans Affairs Community Living Center residents

Taissa Bej MS; Sonya Kothadia MD, MS; Brigid M. Wilson PhD; Sunah Song MS; Janet M. Briggs RN, NP; Richard E. Banks BS; Curtis J. Donskey MD; Federico Perez MD, MS; Robin L. P. Jump MD, PhD


J Am Geriatr Soc. 2021;69(11):3044-3050. 

In This Article


In our national cohort of CLC residents assessed over 9 months of the COVID-19 pandemic, decreasing the criteria for fever from >100.4 to >99.0°F would have increased the number of residents considered symptomatic at the time of their positive test for SARS-CoV-2 by more than 2-fold. While increasing sensitivity, the lower temperature threshold would also have increased the number of residents needing additional assessment for a possible COVID-19 infection by over 4.5-fold. Although the potential increase in labor and costs associated with a lower specificity when using >99.0°F as part of screening criteria are not trivial, the potential benefits outweigh the potential risks. First, using a temperature of >99.0°F to test for SARS-CoV-2 would permit diagnosing a larger proportion of residents with COVID-19 infection based on symptoms rather than on facility-wide screening. Second, it would help identify nursing home residents with COVID-19 infections earlier in the course of their illness. This, in turn, would result in more rapid initiation of infection prevention and control measures that remain the cornerstone of our response to this pandemic. Third, early recognition of COVID-19 infection can lead to increased vigilance for signs of clinical deterioration. This is an important consideration for nursing home residents who are typically frail with multi-morbid medical conditions; early detection of a change in condition can hasten initiation of supportive care, such as fluids and repositioning to improve breathing, and, if needed, transfer to an acute care setting. Finally, early detection of infection may also allow for more timely initiation of medical therapy that is effective against SARS-CoV-2.

Fever is among the most common signs of COVID-19 infection yet detecting fever in older adults is challenging due to lower baseline body temperatures and blunted temperature changes in response to infection. Clinical practice guidelines defining fever in older adults have included both a >2.0°F change from baseline, any temperature greater than 100.0°F, or repeated temperatures of >99.0°F.[10,11] Rudolph et al. reported that only 27% of Veterans with a positive SARS-CoV-2 test had a temperature ≥100.4°F.[2] They also noted that most CLC residents with a COVID-19 infection had at least 2 deviations in temperature that were ≥0.9°F above baseline. Shi et al. used a temperature of >100.0°F to assess residents of a large academic nursing home for signs and symptoms of a COVID-19 infection; even with this lower threshold, fewer than 25% of the residents with a positive SARS-CoV-2 test met criteria for having a fever.[5] A report describing 231 older adults in three nursing homes in Italy found that even when using a temperature threshold of >99.5°F, less than 2% of their residents were recognized as febrile.[20] Using a larger cohort and longer study period, our results support the recommendations made by McConeghy et al. to use a temperature of >99.0°F when screening nursing home residents for COVID-19 infection.[8] A single temperature threshold also makes recognition of fever easier for frontline staff who check vitals and initiate a clinical response.

The CMS has compiled data pertaining to COVID-19 infections from over 15,000 nursing in weekly internals.[21] Between May 18, 2020, the earliest date national data was available, and November 29, 2020, CMS data indicated an average of 183.4 confirmed COVID-19 cases per 1000 residents and an average of 30.5 deaths per 1000 residents with confirmed COVID-19 infection in community nursing homes. Over a comparable time period, from March 1 to November 30, 2020, our study found a lower rate of COVID-19 infections and 30-day all-cause mortality among CLC residents with COVID-19 infections. VA CLCs are integrated within the large and well-resourced VHA healthcare system. As such, VA CLCs were generally less affected by limitations in personnel, PPE, and access to SARS-CoV-2 tests that affected non-VA nursing homes. CLCs are usually in close proximity to VA medical centers where acute care services are readily available. These conditions may have contributed to the comparatively lower rates of infection and mortality observed among residents of VA CLCs compared with those in community nursing homes.

Our results indicated higher survival among CLC residents with asymptomatic infections, without obvious difference among these individuals compared with those who were symptomatic or pre-symptomatic at the time of testing. This result is consistent with previous reports of residents with asymptomatic COVID-19 infections.[22] One reason for this difference may relate to the amount of viral shedding. Previous reports have not found statistically significant differences in the viral load of individuals with symptomatic compared with asymptomatic COVID-19 infections.[23] Correlation between viral loads associated with the positive tests and the symptoms manifested by CLC residents was beyond the scope of this study.

In addition to not assessing viral loads, our study has additional limitations. First, VA healthcare users are predominantly white and non-Latinx males and have a higher burden of chronic medical conditions than the rest of the U.S. population,[24,25] which may limit the generalizability of these results. The findings of high rates of mortality as well as a notable proportion of residents who were asymptomatic at the time of testing within the VA CLC cohort are consistent with previous reports among nursing home residents from both the United States and Canada.[3–5,26–29] Second, we relied upon administrative data to assess the results of RT-PCR tests for SARS-CoV-2. While VA Medical Centers as well as VA COVID-19 Shared Data Resource made efforts to mitigate these false positives and the local and national level, some of the RT-PCR results may have been false positives among individuals with a previous COVID-19 infection that continued to shed non-replicative SARS-CoV-2 RNA.[30] Third, our study period is limited to 9 months. To avoid the potential for fevers as a side effect of the mRNA vaccines confounding the data, we chose to examine the period before the Food and Drug Administration issued emergency use authorization for COVID-19 vaccines.

In conclusion, our analysis suggests that using a lower temperature threshold (>99.0°F) to prompt testing may facilitate early detection of COVID-19 infections, thus limiting the time during which residents thought to be asymptomatic might shed and transmit SARS-CoV-2 to other residents and healthcare personnel within the same congregate care setting. Even nursing home residents who are fully vaccinated may still develop symptomatic COVID-19 infections.[31] Modifying COVID-19 screening protocols in nursing homes so that fever is defined as a temperature >99.0°F will support earlier recognition and testing of infected residents which in turn leads to earlier initiation of supportive care, therapeutic interventions, and, crucially, accelerate the infection prevention and control measures that are central to reducing the spread of SARS-CoV-2.