Accuracy of individual signs and symptoms and case definitions for the diagnosis of influenza in different age groups: a systematic review with meta-analysis

Objective
The objective of this study is to perform a comprehensive systematic review and meta-analysis of the accuracy of signs, symptoms and case definitions for the diagnosis of influenza.

Design
Systematic review and meta-analysis of diagnostic accuracy.

Setting
Inpatient or outpatient setting.

Participants
Three databases (PubMed, CINAHL and EMBASE) were searched through February 2024 for studies of clinical diagnosis of influenza using prospective data collection and a high-quality reference standard. Data were abstracted by researchers working in parallel and resolving discrepancies by discussion.

Primary and secondary outcome measures
Quality was assessed using QUADAS-2. Summary estimates (or ranges) of sensitivity and specificity, likelihood ratio (LR), the Youden Index and the area under the receiver operating characteristic curve were calculated.

Results
The final meta-analysis included 67 studies, each with between 119 and 155 866 participants. Most were judged to be low risk of bias. The signs and symptoms with the highest overall accuracy for all studies based on the Youden Index were any fever (0.32), overall clinical impression (0.28), coryza (0.25), cough and fever (0.25), and measured fever (0.25). Accuracy varied widely by age group. Only the overall clinical impression had a positive LR greater than 2.0. Cough was the most sensitive finding (0.92) with a negative LR of 0.28 in adults. The absence of any fever also had a low negative LR (0.30). The Centers for Disease Control and Prevention (CDC) definition of influenza-like illness (ILI) had good specificity but poor sensitivity in adults, while in infants, it had good sensitivity but widely varying specificity. The European CDC and WHO case definitions for ILI had modest sensitivity and specificity.

Conclusions
Individual signs and symptoms, their combinations, and ILI case definitions have very limited accuracy for identifying persons with influenza. More accurate surveillance and diagnosis will require the development and validation of accurate risk scores or greater use of point-of-care testing.

Leggi
Marzo 2025

The Limited Role for Antiviral Therapy in Influenza

Influenza is associated with substantial morbidity and mortality. Given this, antiviral therapy is commonly prescribed in an effort to prevent these outcomes. We therefore found it surprising that antivirals seem to make little difference for individuals with influenza in outpatient settings, even in the optimized setting of randomized clinical trials.

Leggi
Marzo 2025

Hospitalisation from seasonal influenza among persons with type 1 diabetes: a cohort study from the Swedish National Diabetes Register

Objectives
The aim of this study was to investigate the risk of severe influenza resulting in hospitalisation among adults with type 1 diabetes (T1D).

Design
Nationwide cohort study using register data.

Settings
Data from the National Diabetes Register (NDR) linked to the Swedish Patient Register, Statistics Sweden and the Swedish Population Register.

Participants
Persons with T1D in the Swedish NDR n=35 596 and control persons from the Swedish Population Register matched on age, sex and county of residence, n=155 590.

Primary and secondary outcomes
Hospitalisation from seasonal influenza from October 2013 to December 2019. Season-wise incidence and HRs were analysed in the T1D group compared with controls. Secondary outcomes were associations between clinical variables and hospitalisation due to seasonal influenza for persons with T1D.

Results
There were 347 (1.0%) influenza admissions in persons with T1D and 332 (0.2%) in the control group. The overall incidence rate was 16.9/10 000 person-years in the T1D group and 3.6/10 000 person-years for the control group. Persons with T1D had an unadjusted HR 4.7 (95% CI 4.0 to 5.5) for risk of hospitalisation from influenza during the study period and HR 3.4 (95% CI 2.9 to 4.0) when adjusted for age, sex, socioeconomic factors and chronic medical conditions at baseline. Within the T1D cohort, individuals hospitalised due to influenza were older, were more often smokers, had lower glomerular filtration rate and more often had a previous history of ischaemic heart disease and stroke.

Conclusions
To our knowledge, this is the first large study to highlight that persons with T1D have a threefold higher risk of hospitalisation due to seasonal influenza compared with matched controls from the general population. It is important for healthcare professionals to acknowledge this excess risk, particularly in older persons with T1D, who have cardiovascular risk factors and reduced kidney function.

Leggi
Febbraio 2025