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How to read a PFT test results?

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Have you or someone you know recently completed a PFT/spirometry test? If yes, then it’s only natural to be curious about your test findings. 

However, unless you are a doctor or a medical student, the most likely answer to the question posed in the title of this article is, “No, I have no clue how to read a pulmonary function test report.” 

Even though your health care professional may be the best person to interpret those results for you, it’s always better to have some prior knowledge in order to comprehend your medical practitioner’s advice fully.

Don’t worry if you are clueless about interpreting your PFT test results; we’ve got you covered. Hopefully, by the end of this article, you will be able to understand what all the confusing values stated on your PFT reports mean.

How to read PFT test results?

Values Stated On a Standard PFT Report and What They Mean

Firstly, before we get acquainted with the values stated on a standard PFT report, it is important to mention the factors based on which a “Normal Predicted Value” is calculated. 

The predicted normal for each of the values (that will be mentioned further in this article) varies from person to person and is calculated based on an individual’s:

  • Sex 
  • Race 
  • Height 
  • Age

Using the four determinants stated above, a unique normal predicted value is calculated for each person. Results are considered normal if they are 80% or above the predicted value. (Note that this rule to calculate the normal applies to all the values stated below)

Listed below are some of the values you are likely to find on your PFT results:

Forced Vital Capacity (FVC) 

Forced Vital Capacity refers to the amount of air exhaled after maximum forced inhalation. 

how to read a pulmonary function test report

An abnormal FVC value (below 80%) usually indicates the presence of restrictive or obstructive lung disease. 

FEV1 (Forced Expiratory Volume) 

FEV1 measurement refers to the maximum amount of air exhaled in 1 second. 

FEV1 is used to quantify the severity of breathing problems. Here’s how to interpret your FEV1 score: 

  • 80% or above = normal 
  • 70-79% = mildly abnormal 
  • 60-69% = moderately abnormal 
  • 50-59% = moderate to severely abnormal
  • 35-49% = severely abnormal
  • Less than 35% = very severely abnormal 

If your doctor suspects COPD, then a bronchodilator (airway opening medication) may be used to repeat the FEV1 measurements. In such cases, after bronchodilator administration, FEV1 results are interpreted as follows: 

  • 80% or more = mild COPD
  • 50-79% = moderate COPD
  • 30-49% = severe COPD 
  • Less than 30% =  very severe COPD

FEV1/FVC ratio 

This ratio represents the % of your lung capacity that you can exhale in 1 second. 

A higher ratio (i.e. 80% or above) indicates normal and healthy lungs, whereas a lower ratio indicates a blockage in the air passages. 

 Flow/Volume Graph 

Also known as a spirogram, this graph presents a visual representation of the expiration part of the test. 

Breath flow measured in litres per second is labelled on the X (vertical) axis, while breath volume measured in litres is represented by the Y (horizontal) axis. 

Interpreting this graph may require the assistance of a medical professional; however, to summarize, normally, the graph ascends sharply, followed by an uninterrupted, slow, smooth fall. 

The following characteristics in your graph may indicate abnormalities: 

  • Multiple peaks or an erratic graph 
  • Slow rise to the graph at the start 
  • A late peak in flow  

However, these above-stated factors are generalized, and it’s best to consult your doctor to have your pft test results explained in detail. Also, if you want to know how pft test is done please read our guide.

To Summarize: How to Read PFT Test Results 

  1. Start by checking your FVC and FEV1 values; if those fall under normal parameters, it is very likely that the results of your spirometry are normal. 
  1. If either one of the FVC or FEV1 values is abnormal, refer to the FEV1/FVC ratio instead. If the ratio is normal, then there’s probably nothing to worry about. However, if the ratio is abnormal, i.e. 69% or below, then there is a possibility that you may have some lung disease. 

In case of an abnormal test result, your healthcare provider is likely to order other supporting tests to confirm a diagnosis, e.g. Chest X-ray or blood tests. 

The diseases normally indicated by an abnormal spirometry test result include obstructive diseases, e.g. COPD and asthma or restrictive diseases, e.g. pulmonary fibrosis.

However, all that said, the material provided in this article is strictly for educational purposes and cannot be used as an effective method for diagnosing pulmonary conditions. Please refer to your healthcare provider to have your pft test results explained properly. If you are in New Jersey, you can contact AZZ Medical Associates. Not only are medical practitioners experts at how to read pft results, but your doctor will also be able to guide you regarding further necessary treatments and any precautions you must take to improve. Hope this helps! 

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