How Accurate are Flu Tests?

In primary care offices, we do many types of rapid testing to help us diagnose and treat patients- pregnancy tests, urine tests for infection, rapid strep tests, and of course, rapid flu tests. How accurate are these tests? If a rapid flu test is POSITIVE, it is extremely accurate- 98%. This means they are very SPECIFIC tests- if it says you have it, you have a 98% chance that you really do have the flu, so the likelihood of a false positive is very low. If your rapid flu test result is NEGATIVE, however, you might still have the flu...and your doctor should rely on her clinical judgement. The SENSITIVITY of these tests varies, but averages about 62%, meaning about 1/3 of the time when you DO have the flu, the test could miss it.  (The most recently published meta-analysis of rapid flu tests analyzed 26 different rapid test brands, but all had similar data on accuracy-http://www.ncbi.nlm.nih.gov/pubmed/22371850.)

Why do doctors even use these tests if they are not super sensitive? Because it affects our treatment plan. If we have confirmation that someone has the flu (with a positive test), then we can feel more confident in NOT prescribing an antibiotic, and limit our conversation to pros/cons of taking an antiviral medication as well as medications for symptomatic relief. This step greatly reduces unnecessary antibiotics, which is critical in an era of increasing antibiotic resistance.
Additionally, knowing a patient definitely has the flu helps us advise them about returning to work/school/activities, since we know flu stays infectious for up to a WEEK. (So STAY HOME at least several days, and until you are fever-free for at least 24 hours!)

If you had the flu vaccine, will that affect your rapid flu test?  If you had a shot- no. If your flu vaccine was the intranasal spray, there is a chance that you could have a false positive test. Studies have shown that in the first several days after receiving the nose spray vaccine, people may test positive for the flu (even though they are not infected.)

During epidemic years of the flu (including 2015) the CDC encourages doctors to treat all high risk individuals with suspected flu with antiviral medications, and in fact, last week the CDC put out a special Health Update.

Who should be treated with SUSPECTED illness? Some are obvious- anyone hospitalized, patients in nursing homes, and people with immune problems, significant chronic problems (lung or heart disease, for example) or with severe illness such as pneumonia. However, HIGH RISK also includes all otherwise healthy children under the age of two years,  adults over the age of 65, and women who are pregnant or have just delivered their baby within the past two weeks. There are also other less common subgroups that are high risk such as people who are very obese (BMI >40), American Indians or Alaska natives, and youth under 19 who are on chronic aspirin therapy.

Who should be treated with CONFIRMED illness? Anyone in the high risk categories above should be treated with antiviral medications if they have a positive test, because treatment definitely decreases severe complications, hospitalization and even death. Otherwise healthy, active adults who test positive for the flu should have a discussion with their physician about taking the antiviral medications. When taken within 48 hours of the onset of flu symptoms, these drugs have been shown to decrease the duration of the flu by one or two days...which can make a big difference to a student, parent or employee. However, these medications are not without side effects, and for some people, they may aggravate flu symptoms- particularly nausea. In controlled studies, the antiviral medications only cause about 10% more nausea/headaches/fatigue than placebo, but there is no doubt that in a minority of patients, the medicine causes more side effects than they are worth. However, since you have the FLU when you are taking the medications- you already likely HAVE nausea, headache, fatigue, etc- so it is often difficult to sort out. In my family, half of us can tolerate the antiviral medications with zero problems, and half...barely keep the pills down long enough to know.

BOTTOM LINE: If you have flu symptoms, get to the doctor as soon as possible (especially if you would consider taking antiviral medications), and understand that a positive test is REALLY positive, but a negative test does not definitely rule out the possibility of the flu. 

Flu Without Fever?

Can it be? Should you even wonder if you have the flu if you don't have a fever? Unfortunately, YES. While it is true that the classic presentation of seasonal flu includes an often HIGH fever, body aches, fatigue, sore throat, cough and abdominal symptoms like nausea, pain or diarrhea, no single symptom is absolutely necessary for a diagnosis.  Children under the age of 6 years frequently do not have fever and cough with their flu symptoms. This year in particular, I have seen more cases of flu with purely fatigue and stomach symptoms...including one in our family this week.

The incubation period for influenza averages about two days, so that means that you are exposed to flu 1-4 days before you have symptoms. Unfortunately, you are contagious (spreading germs yourself) the day BEFORE you have intense symptoms, and then continue to be contagious for roughly 5 - 7 days. Whether or not you have FEVER.

What's my point? We all have to be responsible about not spreading the flu. It's hard for anyone to miss work/school/sports, but when we go back too soon, we are just increasing the chance of passing on this illness to our peers. When SHOULD we return to work/school? If you HAVE fever, it's a clear recommendation to wait to go back until you have been completely fever-FREE for 24 hours, without the benefit of tylenol or ibuprofen (which obviously can lower temperatures, and therefore, mask a fever). If you do NOT have fever, but have a positive flu test, then it is less obvious when you should go back, but on average most otherwise healthy people will need to be at home for at least three days. If you are vomiting and having diarrhea, a good rule of thumb is to wait for 24 hours after these symptoms subside to return to work/school. As a parent, I cringe every time I here someone talking about sending their kid to school after that same kid was up "all evening last night vomiting" or they comment nonchalantly, "I know she's wiped out, but she hasn't thrown up since lunch yesterday... and they have a huge test this week."

The flu is spread via respiratory secretions, and this can be transmitted directly by coughing or sneezing (or simply by talking) or indirectly by transfer as the infected person touches their mouth or nose, then touches surface (leaving the virus there) and then the next person touches that surface before touching their own mouth/nose. Remember all of this is microscopic, not visible.

When we DO go back, perhaps we should at least take some antibacterial hand sanitizer with us. And tell your friends and family to get the flu vaccine. True, this year's vaccine is not a great match, but at least it lessens the severity of the flu if you still get it.

BOTTOM LINE: Please, if you get the flu, do your part to stop spreading this disease and STAY HOME from work, school, sports, (and restaurants, grocery stores, Starbucks, whatever!) until you feel significantly better AND are FEVER-FREE (and puke-free) for at least 24 hours without taking medicines to stop/blunt those symptoms.

Will You "Cervive" in 2015?

Is 2015 the year you finally truly prioritize YOUR health? The majority of Americans include weight loss and possibly exercise in their New Year's Resolutions each year...and do really well on their strict diets for a few days or maybe even a few weeks. While I absolutely applaud attention to weight and activity levels, I want to encourage you to think beyond diet and exercise for your 2015 health resolutions. (And I will spend time in future blogs this month talking more about what diets work best, but today I want to shift the focus...)

January happens to be Cervical Cancer Awareness month, so women- how about starting your 2015 Resolution list with scheduling your "annual" exam, especially if your last "annual" was way more than a year ago? The GOOD news is that screening recommendations have changed quite a bit, so women no longer need to have Pap tests every year. Current guidelines tell us for young women to have their FIRST Pap test at age 21, then (assuming tests do not show a problem) every 3 years between 21-29, and then after age 30, testing can actually occur simply every 5 years (by using both the Pap test and a specific HPV test combined).

In the United States, cervical cancer is still diagnosed in over  12,000 women per year, and tragically, still causes over 4000 deaths per year. We can do better! The vast majority of women with cervical cancer have little to NO symptoms- this is a silent killer. While prevention (with the HPV vaccine) is optimal, early detection absolutely saves lives- so do NOT put off getting your Pap test.

While most of us have run 5K's or worn PINK for breast cancer awareness, few people know or talk about their diagnosis of cervical cancer. Tamika Felder, a now 13 year survivor of cervical cancer, is leading the charge to increase personal and community support for cervical cancer. For my fellow AUSTINITES- if you or someone you love has been diagnosed with cervical cancer (whether that diagnosis was recent or many years ago), please let them know about CERVIVOR SCHOOL- a four day learning, connecting and revitalizing retreat NEXT WEEK, starting Thursday evening, 1/15/15 through Sunday afternoon.

BOTTOM LINE: Women, if you are due for a Pap test, please move that to the top of your 2015 Resolution list!