Does this patient have influenza?

Area of Science:

• Infectious Diseases
• Clinical Diagnostics
• Epidemiology

Background:

• Influenza vaccination reduces but does not eliminate influenza risk.
• Accurate and rapid clinical diagnosis of influenza is essential for patient management, particularly during antiviral shortages.

Purpose of the Study:

• To systematically review the diagnostic accuracy of influenza symptoms and signs.
• To evaluate the performance of rapid influenza diagnostic tests.

Main Methods:

• Systematic literature search of MEDLINE and bibliographies (1966-2004).
• Inclusion of studies reporting operating characteristics of symptoms/signs against a criterion standard.
• Data abstraction and likelihood ratio (LR) estimation by two independent reviewers.

Main Results:

• No single symptom or sign reliably confirmed or excluded influenza in the general population.
• Absence of fever, cough, or nasal congestion decreased influenza likelihood (LR < 0.5).
• In older adults (≥60 years), combinations of fever, cough, acute onset, malaise, and chills increased influenza likelihood (LR > 2.0).

Conclusions:

• Clinical findings alone are insufficient for definitive influenza diagnosis.
• Clinicians should consider community influenza activity and utilize rapid diagnostic tests for informed management decisions.