My daughter was diagnosed with CF at the age of 2 in 1991. She's 28 yo and as of a few years ago, her mutation hasn't turned up in genetic testings. We know whatever she has is a milder form of CF because of the shape her lungs are in. When issues arise, all ER doctors are always shocked to hear she has CF once they listen to her and see Xrays. When she was first diagnosed, she was having lots of respiratory issues and was hospitalized frequently. BUT we started her on inhaled tobramycin (this was before TOBI existed) and it turned things around in an almost dramatic fashion for her. She went from almost monthly hospitalizations for four years to not being hospitalized for 2 - not even a SINGLE respiratory illness! During her "good" period, I started reading tons of literature (when she was diagnosed, I'd read everything I could find on CF but NOT on the possibility of illnesses/genetics/etc. that sometimes mimic CF like symptoms). I convinced myself she perhaps had something different. I went to her pulmonary specialist who always treated me as an equal (we were so very fortunate when I look back on things) and he told me how there can be a false negative but there are no false positives with CF. I continued to argue so he brought in his younger, new partner who attended CF conferences and the new dr. said, "Richard, WHY not just let her do it? It's a sweat test - it's not an invasive test." I said, "my point EXACTLY". We did it and she tested positive. Over the years, we have seen her deal with SO many issues with her lungs at times, her sinuses, then it was her kidneys, then digestive, recently it's been issues with some her ovaries, endometriosis, etc. So, we're convinced she has it BUT she definitely has her own form of whatever mutation it is she has. Her FEVs are great for a 28yo., she's only on a couple enzymes for digestive, she does inhalers daily and moves to treatments when she feels anything coming on. My point to this long ramble is... YOU are the person with CF and it is always in your best interest to speak up. Always. My daughter has oftentimes known she needed to go on IVs even when the xrays or tests came back not really showing the need for them. As soon as she'd get about 24 hours in, mucous would just start almost pouring out of her, her xrays and lungs would be radically different but because her doctors listened to her, she'd have a head start on her healing process. I've learned to never question her when she calls and says, we're headed to the ER (she's married now) - I've contacted Dr. __ and told him it's time and I'm not making progress on the plan we've had these last X number of days. Or, headed to ER, I have this weird pain in my gut and it's not normal. She is right 99.9% of the time. Her pulmonary specialist (same doctor) always tells people to listen to her because she knows her body better than anyone else. So always, always, always trust yourself. It's okay if you take the test and it comes back positive again. You're already living the life of a person with CF so you know what it means. But what if? If you don't ask, you'll never know. No matter what you decide, good luck. And congratulations on speaking up about TOBI. My daughter was fine with inhaled tobramycin (you can't get it for use like that since TOBI came out) but TOBI irritates her bronchial tubes and she's never cultured psuedo so she does not do TOBI either.