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Published on January 12th, 2015

Influenza Testing Protocol

St Luke’s University Hospital is pleased to announce that starting January 7, 2015, “Simplexa PCR” test for influenza A, influenza B and respiratory syncytial virus (RSV) will be performed in the Microbiology laboratory (Test code:4511). As indicated in the past communication and recommendation by our infectious disease physcian’s that PCR testing is more sensitive and so should be utilized for diagnosis in replace of Rapid Influenza test which has low sensitivity.

  1. If clinical suspicion for influenza is high, presumptive treatment may be elected, since not all patients need to be tested. Where diagnostic testing is clinically indicated in adults (age > 18 y/o) with suspected influenza or RSA, we strongly recommend that a sensitive “Simplexa PCR” be ordered as the initial test, in place of the “rapid influenza screen”. The “Simplexa PCR” is orderable as test code: 4511 in our hospital systems and as “Influenza A/B and RSV, PCR” in Allscripts. Because the turnaround time of the PCR test is 24 – 48 hours, supportive or presumptive patient treatment may be considered while awaiting test results. Test results will be reported as follows:

    Influenza A: Detected or Not Detected
    Influenza B: Detected or Not Detected
    RSV: Detected or Not Detected

  2. In certain pediatric populations or when attempts at rapid diagnosis (within 6 hours of specimen receipt in lab) are a medical priority, “rapid influenza screen with reflex to PCR” (tests for both influenza A and influenza B) and/or “RSV antigen” may be ordered provided the specimen is collected as described in item 3., below. If “rapid influenza screen with reflex to PCR” is negative for both influenza A and influenza B or an invalid result is obtained, the results will be reported and all such specimens will be submitted by laboratory personnel for reflexive “Simplexa PCR” testing, to be reported is 24 – 48 hours later as described in item one, above.

    “Rapid influenza screen with reflex to PCR” is orderable as test code 4104 in our hospital systems and as “rapid influenza screen” in Allscripts. “RSV antigen” test is orderable as test code 4520 in our hospital systems and as “RSV antigen” in Allscripts.

  3. All specimens collected for “Simplexa PCR”, “rapid influenza screen” or “RSV antigen” must be obtained by a flocked nasopharyngeal swab (NP swab) placed immediately into Universal Transport Media (UTM), M4 media or viral transport media and sent to the laboratory refrigerated. Only nasopharyngeal swabs will be accepted for testing for Simplexa PCR. If other specimen collections including nasopharyngeal aspirates, throat swabs are submitted for “rapid influenza screen”, they will be processed and the rapid result reported. However, if the rapid result is negative, the specimen will be reflexively submitted for viral culture, with an expected turnaround time of 48 – 72 hours. Please call the laboratory for instructions to order supplies such as NP swabs, if necessary. Please note that laboratory outpatient service centers are not trained to collect NP swabs. Respiratory therapy department at Bethlehem campus is trained to collect such specimens, however.

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