Your 60 year old patient says he feels horrible. Fever, chills, body aches. His grandson has similar symptoms last week. His exam is significant for fever of 102, P105, 140/76, SpO2 97%,  upper respiratory congestion, with clear lungs, normal heart sounds and benign abdomen.

Your attending is concerned he has the flu, says: “Hey, lets test for it”. Do you know how to make that happen? From a logistic standpoint?

-The test to order is “Influenza DFA”

-You (the MD) needs to collect it. Go to the Peds side utility room and get a “Floq” swab from the counter and some Hank’s media from the refrigerator. It looks like this:


-Then you have to swab the patient’s nose. Have the patient blow their nose first (you don’t want mucus, you want cells). Take the swab out of the container, place it in their nose. Move straight back posteriorly about half way the distance to the ear until you feel hold up. Rotate the swab several times to get a good sample (about 10-15 seconds in the perfect world). The test is only as good as the sample, so stay in there as long as the patient will tolerate it.

Check out this short video for a demonstration:

-Then break the swab off into the Hank’s media. Give it to the patient’s nurse or label it and send it yourself.

-The test takes about 2 hours to come back –

During the Day -> 95% sensitivity 95% specificity against cultures as gold standard (reported by Mt. Sinai labs, although studies have show more like 70-100% and 80-100% sens/spec respectively for this type of test)

During the Night -> Lab will run a rapid test which supposedly has a sensitivity 92-98% and specificity 100% against cultures as gold standard (reported by Mt. Sinai labs, studies quote more like 65-55% sensitivity and 98% specificity). The lab will confirm in the morning with a official DFA if the rapid was negative.

Then the next question arises, what do I do with the information once it results…but let’s talk about that another day.

Further reading:

About rapid flu tests…


Gavin, Patrick J., and Richard B. Thomson Jr. “Review of rapid diagnostic tests for influenza.” Clinical and Applied Immunology Reviews 4.3 (2004): 151-172.


May 2024