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  • Understanding Your Tests

Understanding Your Tests | My Cayston Community™


Clinic visits can be stressful. Sometimes patients and families can get nervous a few days ahead of the appointment. However, care decisions around the course of treatment are usually dependent on the results of your PFTs (pulmonary function tests), Body Mass Index (BMI) measurements, culture results, imaging studies, and other lab tests. I have had more than a few patients tell me during the visit that they were “nervous about what their numbers would be.” Some patients will even delay or skip a visit due to this worry. Clinic visits should never make you feel so stressed out that skipping them is the answer. Your care team is there to support you and to partner with you, so communicating with them is an essential part of your care. Partnership with your CF care team means that you as the patient or caregiver are the most important part of that team, and your voice should always be heard. For example, if you have been experiencing more symptoms (eg, cough, wheezing, etc) than usual, be sure to let your care team know. They might not always ask, but it’s important that they are aware!

Your care team is there to support you and to partner with you, so communicating with them is an essential part of your care.

Most quarterly visits start with a measurement of weight and height. This is then used to calculate BMI. BMI is an important number because there are strong data to support a close connection between lung function and BMI. For people with CF, the Cystic Fibrosis Foundation recommends the following BMI goals:

  • Under the age of 21 = BMI above the 50th percentile
  • Women (over 21) = BMI of at least 22
  • Men (over 21) = BMI of at least 23

Next, pulmonary function tests (PFTs, or the “blowing test”) are performed. This is arguably the part of the visit that can certainly be impacted by nerves. Some patients get so worried about what they may “blow” that their technique for the test is impacted, and their results end up being lower than expected. Just remember that this testing is only one part of the picture of your health status. In general, the better your Forced Expiratory Volume in 1 second (FEV1) is, the better you are probably feeling at the time of the test, although there can be some variation. The term “baseline” is used to describe the spot your FEV1 usually is.

All other lab testing such as culture results, imaging studies, and blood labs are also routinely interpreted and used to get a full picture of the patient’s clinical health. CF cultures are a routine part of quarterly clinic visits. Depending on whether you can produce enough sputum, you may get a specimen cup into which to spit the sputum or have a throat swab done instead. In some cases, the care team will do what is called a sputum induction, which is an attempt to get an individual to bring up sputum. The sputum induction involves administering a medication that will help to make the mucus thin and easier to produce. This doesn’t always work, but we still try from time to time, since some of the culture tests that the care team looks for cannot be done with just a throat swab. After the clinic collects the culture, it is sent to the lab, where it is tested to find out what bacteria are growing. The results of this information are then used to guide treatment decisions. To learn more about diagnosing Pseudomonas aeruginosa (Pa), read my other article here.

Combining this information with the information gathered when talking to each patient helps a CF provider know what treatment plan to prescribe and/or what changes to recommend. Looking at one test result alone will not give a full view of what is going on for a patient. But, putting all the pieces together, like a puzzle, allows the provider to see a full, clearer picture of how they are doing.