A Basic App for Calculating Predicted and Low Normal Spirometry Values

Whether evaluating patients for asthma or for COPD, spirometry is a critical and required part of the diagnostic process. Some primary care practices perform office spirometry, while many of us refer patients to PFT clinics and/or pulmonologists or allergists for evaluation and testing. Interpretation of spirometry can be challenging and not knowing normal values can be a limitation although most spirometers provide results that include predicted values in addition to the patients’ actual results. 

According to both the 2019 Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) and Global Initiative for Asthma (GINA) guidelines, spirometry must be performed as part of the work-up. Smoking remains the most common cause of COPD and it remains highly relevant — despite the recent decrease in tobacco use in the United States. Though the nation currently faces an explosion of e-cigarette use especially in teenagers which have been linked to numerous fatalities as well as to an increased risk of both asthma and COPD. A postbronchodilator FEV1/FVC < 70% is consistent with a diagnosis of COPD. Spirometry classifications are then broken down by the patient’s FEV1. 

Previously on iMedicalApps, we favorably reviewed the PFT Eval app by Dr. Joshua Steinberg, the GOLD Pocket Guide COPD app, the COPD Pocket Consultant app, and numerous asthma apps as well as medical calculator apps such as MDCalc, Calculate by QxMD, and MedCalx. This new standalone Spiro Calculator is unique in that it performs only this function and uses the internationally accepted 2012 Global Lung Initiative (GLI) standards. The app is easy to use and rapidly displays the results, but it contains no references, basic developer information, or how to interpret the results. The app is also only available for iOS currently and costs $.99. 

Evidence-based medicine

The app doesn’t contain any information on the formula used for its calculations or references within the app itself. In the App Store, it states the app utilizes the standards from the 2012 Global Lung Initiative. These 2012 GLI standards are considered to be the reference standard to be used worldwide. The app would benefit from references to these standards and other spirometry related articles. 

Who would benefit from this App?

Any healthcare provider who performs office/hospital spirometry including students, NPs, PAs, family medicine, internal medicine, pulmonologists, and respiratory therapists.


o $.99


o Simple to input data/view results

o Includes both predicted values and lower limits of normal values

o Fills a void for standalone calculator for spirometry values


o No background information/directions/interpretation, no European values

o  Relatively expensive for a standalone calculator available in other apps

o  Not available for Android


The Spiro Calculator does just one thing: predicted and low normal spirometry values. It performs this calculation quickly and accurately. The app does not contain any information about its references, alternatives for calculations, or how to interpret the results. It is a bare-bones calculator, but one that is not included in most calculator apps. However, it is available in MedCalX via in-app purchase. For a standalone calculator, it may be too expensive for some. For those who need these values quickly and on their mobile device, this app could be a good option, but likely has limited generalizability/use across primary care except those performing office spirometry (and nearly all spirometers will provide this information). 

Overall Score

o 3.5 stars

User Interface

o 3.5 stars

Easy to use interface with user inputting date of birth and height (no ability to just put in age in years or height in inches, however).

Multimedia Usage

o 3.0 stars

App calculates the predicted and low normal spirometric values using GLI 2012 standards but has no additional functions, directions, references, etc.   


o 4 stars

App is $.99.

Real-world applicability

o 3.5 stars

The Spirometry Calculator is a bare-bones reference calculator for those regularly performing spirometry and need the reference values on their device. The app works well but lacks any additional information on PFT interpretation, alternative references to calculate values, etc. A nearly identical calculator is available on MedCalx which contains hundreds of additional calculators for free and via in-app purchase.  

Device Used For Review

o iPhone 11 Pro running iOS 13.3

Available for download for iPhone, and iPad. Not available for Android at this time.

Disclaimer: The views expressed are those of the author(s) and do not reflect the official policy of the Department of the Army, the Department of Defense or the U.S. Government.