This document provides interim guidance for state and local health departments, hospitals, and clinicians participating in surveillance activities regarding which patients to prioritize for testing by RT-PCR for influenza surveillance. Based on the continuing spread of 2009 H1N1 virus since the spring and continuing into the fall and increased demand for influenza testing, these guidelines have been developed in an effort to prioritize patients for testing by RT-PCR for influenza for surveillance purposes.

The recommendations in this interim guidance are made to support surveillance activities for influenza; they do not address prioritization of testing for other purposes. Confirmation of 2009 influenza H1N1 virus infection may also be important for clinicians taking care of patients. Guidance on prioritization of diagnostic testing for clinical care purposes can be found at Interim Recommendations for Clinical Use of Influenza Diagnostic Tests During the 2009-10 Influenza Season.

Use of real-time reverse transcriptase-polymerase chain reaction (rRT-PCR) testing is important for surveillance in order to identify which influenza A subtypes (e.g. 2009 H1N1 versus seasonal H1N1 or H3N2 viruses) are circulating. For surveillance purposes, CDC recommends that the following patients be prioritized for rRT-PCR testing:

Patients presenting to healthcare providers participating in the US Outpatient Influenza-like Illness Surveillance Network (ILINet) who meet the surveillance case definition of influenza-like illness.

Hospitalized patients for whom influenza infection is clinically suspected despite a negative result on a rapid influenza diagnostic test.
Patients whose deaths are believed to be influenza-associated.

Source: Centers for Disease Prevention and Control