Is it appropriate to diagnose a patient (pt) with influenza if they are symptomatic with exposure, despite a negative point-of-care test (POC) result?

From the Guidelines

It is appropriate to diagnose a patient with influenza despite a negative point-of-care test if they have typical symptoms and known exposure, as clinical judgment should guide diagnosis and treatment decisions. The provided evidence from the Morbidity and Mortality Weekly Report 1 emphasizes the importance of early antiviral treatment to reduce the risk of complications from influenza, particularly in high-risk patients. Although the report does not directly address the issue of negative point-of-care tests, it highlights the need for empiric antiviral treatment in patients with suspected influenza, especially those at higher risk for complications.

Key Considerations

• The sensitivity of point-of-care influenza tests is limited, ranging from 50-70%, which means false negatives are common, especially early in the illness 1.
• Clinical judgment should guide diagnosis and treatment decisions, taking into account the patient's symptoms, exposure history, and risk factors for complications.
• Empiric treatment with neuraminidase inhibitors like oseltamivir (Tamiflu) may be warranted in patients with classic influenza symptoms during flu season or with confirmed exposure to someone with influenza.
• Treatment decisions should consider the patient's risk factors for complications, symptom severity, and time since symptom onset, as the virus sheds most heavily in the first 3-4 days of illness.

Treatment Recommendations

• The standard regimen for oseltamivir is 75mg twice daily for 5 days for adults, with treatment ideally started within 48 hours of symptom onset for maximum effectiveness 1.
• Patients with suspected influenza should complete antiviral treatment for a full treatment course regardless of negative initial test results unless an alternative diagnosis can be established and clinical judgment suggests that influenza is unlikely.

High-Risk Patients

• Persons at higher risk for influenza complications who are recommended for antiviral treatment for suspected or confirmed influenza include children aged <2 years, adults aged ≥65 years, and those with chronic pulmonary, cardiovascular, renal, hepatic, hematological, or metabolic disorders 1.

From the Research

Diagnosis of Influenza

• The diagnosis of influenza can be challenging, as it is difficult to distinguish clinically from other acute respiratory infections 2.
• Point-of-care tests (POCTs) for influenza can help initiate early effective antiviral treatment and isolation 2, 3.
• However, a negative POCT result does not necessarily rule out influenza, as the sensitivity of these tests can be low 4.

Clinical Decision-Making

• Clinical decision-making for patients with suspected influenza should be based on a combination of clinical presentation, exposure history, and laboratory test results 2, 3.
• Even if a POCT is negative, a patient with symptomatic exposure to influenza may still be diagnosed with the disease if their clinical presentation is consistent with influenza 2.
• Antiviral treatment may still be initiated in patients with a negative POCT result if their clinical presentation is consistent with influenza, particularly if they are at high risk of complications 5, 6.

Point-of-Care Testing

• Point-of-care testing for influenza can influence prescribing and testing decisions, particularly for children in emergency departments 3, 4.
• The use of rapid molecular tests, such as FilmArray, can reduce hospitalization and oseltamivir administration in children presenting with influenza-like illness 4.
• However, the implementation of POCTs may not always lead to improved patient outcomes, and further research is needed to clarify their utility and tolerability in different patient populations 3.