Quantitative Definition of Fever Needs a Change: A Longitudinal Study from the Hospital Workers and their Family Members

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Introduction: The age-old definition of fever was derived using cross-sectional population surveying utilising old techniques without considering symptomatology. However, the diagnosis of fever must be made only in the presence of associated symptoms that can distinguish it from the mere asymptomatic physiologic rise of temperature. Aim: Analysis of symptoms to re-define the cut-off of fever based on symptomatology. Materials and Methods: A longitudinal study on the healthy population of Uttarakhand, India was conducted and the population was followed up from July 2019 to September 2020. Healthy staff and students of All India Institute of Medical Sciences (AIIMS), and their family members between 4-100 years of age were chosen. Participants were advised to self-monitor oral temperature with a standard digital thermometer in either left or right sublingual pocket and record it in the thermometry diary. The study was considered complete if the participant had all the three phases of the study (i.e., prefebrile, febrile, and postfebrile phases) or completed the duration of the study. The febrile phase was defined when the participants subjectively ‘felt feverish’. Associated symptoms like fatigue, warmth, headache, and feeling malaise were also recorded. Results: Mean age of the participants was 24.24±5.92 years, and 52.1% (75) were males. Per protocol analysis was done for febrile participants (n=144, temperature recordings=6544). The mean febrile phase temperature was 100.25±1.440 F. A temperature of 99.10 F had maximum diagnostic accuracy for feeling feverish (98.2%), along with one (98.3%) or two (99%) associated symptoms. Summer and spring months showed higher temperatures (100.38±1.44 v/s 99.80±1.49, p-value<0.001), whereas no significant temperature difference could be noted amongst the genders. Conclusion: Based on the findings of this study, the revised temperature cut-off to define fever should be 99.10 F along with one or two associated symptoms.