Accuracy of short-term insomnia onset and composite clinical score in the differential diagnosis of common cold and influenza: A cross-sectional study
Influenza (IA) and the common cold (CC) may present with similar symptoms. However, rapid IA diagnostic tests have a low sensitivity during the early stages of the disease. Therefore, various diagnostic tools are needed. Mild short-term insomnia (MSTI) occurs in patients with CC, but the incidence in patients with IA remains unknown. Hence, we hypothesized the difference between the day of onset of MSTI and the date of fever occurrence in IA to be shorter than that in CC. This study aimed to investigate the incidence of MSTI in patients with CC and IA with fever (≥ 37.5℃) and the risk of developing acute-onset MSTI (alone or as part of a composite clinical score) to aid in the differential diagnosis during the early disease stage. The relationship between MSTI and other symptoms was analyzed using quadratic logistic regression to model the number of IA cases with composite score day progression from the onset of fever, namely origin day 0. The results revealed a day 0 axis-symmetrical and inverted U-shaped relationship between the onset days of the composite scores and estimated probability of IA. The coefficient of the quadratic term is negative and significantly different from zero, supporting the hypothesis that the onset of IA-related MSTIs is more acute than that of CC-related MSTIs. Principal component analysis was also applied to the onset days for five IA- and CC-related symptoms, in addition to fever (MSTI, cough, rhinorrhea, sore throat, and headache). The maximum day difference in fever onset and at least one additional symptom was established as the cutoff day between IA and CC using receiver operating characteristic analysis. The cutoff value was confirmed based on the MSTI-onset derived variables using logistic regression. This cross-sectional survey included 100 and 106 CC and IA patients, respectively. The optimal cutoff day were one day before and one day after the onset of fever. For those with CC and MSTI beyond the cutoff day, the diagnostic sensitivity, specificity, and positive likelihood ratio were 7%, 99%, and 7.42, respectively. For patients with CC and any composite clinical score symptoms beyond the cutoff day, the sensitivity, specificity, and positive likelihood ratios were 36%, 92%, and 4.77, respectively. A composite clinical score and MSTI onset with a cutoff day of one day before and after fever onset may help distinguish between early stage CC and IA.