PFT Interpreter

Pre-bronchodilator spirometry, lung volumes and diffusing capacity interpreted by the ATS/ERS 2022 algorithm (GLI z-scores), with a percent-predicted fallback when z-scores are not reported.

Patient and reference method

demographics optional; blanks allowed
Computed values fill empty % pred and z-score fields; fields you typed are kept until Recompute.

Spirometry (pre-bronchodilator)

L · % pred · z
ParameterMeasured% predz-scoreLLN
FEV1L
FVCL
FEV1/FVCratio or %
PEFL/s, optional

Post-bronchodilator

Lung volumes

plethysmography or dilution
ParameterMeasured% predz-score
TLCL
RVL
RV/TLCratio or %

Diffusing capacity

single-breath CO
ParameterMeasured% predz-score
DLCOmL/min/mmHg
VAL
KCO (DLCO/VA)mL/min/mmHg/L
Interpretation

    Report text

    
    
    
    
    
      
    Physiologic correlation
    patterns to consider, not a diagnosis
    
      
      
    
      
  
      

      


      
  
      Reference values
      computed from the GLI equations for the demographics entered
      
  
      

      


      
  
      Algorithm path
      highlighted nodes are the route the current values took
      
      
      
        
      
          
            
              
              
            
          
        
      
        
      Highlighted nodes and arrows are the path the current interpretation took. Pills are decisions, boxes are outcomes; the bottom row shows the four assessments made alongside the pattern.
      
      
      

      


      
  
      
    References, thresholds and method
    
      Pattern and severity are assigned from pre-bronchodilator values. z-score thresholds: LLN −1.645, ULN +1.645; severity for FEV1 and DLCO: mild −1.65 to −2.5, moderate −2.51 to −4.0, severe below −4.0 (Stanojevic et al., Eur Respir J 2022). Percent-predicted fallback uses LLN 80 %, ULN 120 %, fixed ratio 0.70, and the ATS/ERS 2005 severity grades. Bronchodilator response: change in FEV1 or FVC above 10 % of the predicted value (2022), with the legacy 12 % and 200 mL criterion shown for reference. When age, sex and height are entered, predicted values, LLN, % predicted and z-scores are computed from the GLI equations named in the Demographics panel; otherwise enter the lab's GLI output.
      
    
      Equation sets: FEV1, FVC and FEV1/FVC from GLI Global 2022 (Bowerman 2023, race-neutral, the default per the 2023 ATS statement on race-neutral reference equations; the ancestry selector is ignored and disabled) or from GLI-2012 (Quanjer 2012, ancestry-specific), both 3 to 95 years; TLC, RV and RV/TLC from GLI-2021 static lung volumes (Hall 2021, European-ancestry data, 5 to 80 years); DLCO, VA and KCO from GLI-2017 TLCO (Stanojevic 2017 with the 2020 correction, 5 to 90 years, mL/min/mmHg). LLN and ULN are the 5th and 95th centiles (z = ±1.645).
      
      
        
        
      1. FEV1/FVC below LLN: airflow obstruction. If FVC is also low, TLC decides between a mixed defect (TLC low) and air trapping with pseudo-restriction (TLC normal). Low ratio with normal FEV1 and FVC can be dysanapsis.
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      2. Ratio normal and FVC low: TLC low means restriction, TLC normal means a nonspecific pattern. Without TLC the spirometry is a restrictive pattern or PRISm (preserved ratio, impaired spirometry), and TLC is required.
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      3. Severity of any ventilatory defect is graded on the FEV1 z-score.
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      4. TLC above ULN: hyperinflation. RV or RV/TLC above ULN: air trapping. FVC reduced at least 10 percentage points below TLC: complex restriction.
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      5. DLCO below LLN is graded on its z-score and read with VA and KCO: low VA with normal or high KCO points to incomplete expansion or lost units; low KCO with normal VA points to the alveolar-capillary membrane or vasculature; both low favor parenchymal disease.
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      6. DLCO is adjusted for hemoglobin when a value is entered and the lab has not corrected it (Cotes equation, men 1.7Hb/(10.22+Hb), women 1.7Hb/(9.38+Hb)).
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      7. FEV1 (mL) / PEF (L/min) above 10 raises the question of upper airway obstruction (Empey index).
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      8. Reference values use the GLI LMS method: M = exp(a0 + a1·ln(height) + a2·ln(age) + ancestry terms + Mspline), S = exp(p0 + p1·ln(age) + ancestry terms + Sspline), L = q0 + q1·ln(age) + Lspline, z = ((measured/M)L − 1)/(L·S), LLN = M·(1 − 1.645·L·S)1/L. Spline values are read from the published 0.25-year lookup tables with linear interpolation. GLI-2021 volumes use age and height on the scale given in Hall 2021 Table 3 (RV and RV/TLC use untransformed age and height). GLI-2017 predicted DLCO and KCO are adjusted for hemoglobin, carboxyhemoglobin above 2 % and test-site altitude when those are entered (ATS/ERS 2017 conventions, equations 31, 32, 34 and 37).
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      Citations
      
    
        
      
      1. Stanojevic S, Kaminsky DA, Miller MR, Thompson B, Aliverti A, Barjaktarevic I, Cooper BG, Culver B, Derom E, Hall GL, Hallstrand TS, Leuppi JD, MacIntyre N, McCormack M, Rosenfeld M, Swenson ER. ERS/ATS technical standard on interpretive strategies for routine lung function tests. Eur Respir J. 2022 Jul 13;60(1):2101499. doi: 10.1183/13993003.01499-2021. Print 2022 Jul. PMID: 34949706.
        2. 
      
      2. Pellegrino R, Viegi G, Brusasco V, Crapo RO, Burgos F, Casaburi R, Coates A, van der Grinten CP, Gustafsson P, Hankinson J, Jensen R, Johnson DC, MacIntyre N, McKay R, Miller MR, Navajas D, Pedersen OF, Wanger J. Interpretative strategies for lung function tests. Eur Respir J. 2005 Nov;26(5):948-68. doi: 10.1183/09031936.05.00035205. PMID: 16264058.
        3. 
      
      3. Quanjer PH, Stanojevic S, Cole TJ, Baur X, Hall GL, Culver BH, Enright PL, Hankinson JL, Ip MS, Zheng J, Stocks J; ERS Global Lung Function Initiative. Multi-ethnic reference values for spirometry for the 3-95-yr age range: the global lung function 2012 equations. Eur Respir J. 2012 Dec;40(6):1324-43. doi: 10.1183/09031936.00080312. Epub 2012 Jun 27. PMID: 22743675; PMCID: PMC3786581.
        4. 
      
      4. Bowerman C, Bhakta NR, Brazzale D, Cooper BR, Cooper J, Gochicoa-Rangel L, Haynes J, Kaminsky DA, Lan LTT, Masekela R, McCormack MC, Steenbruggen I, Stanojevic S. A Race-neutral Approach to the Interpretation of Lung Function Measurements. Am J Respir Crit Care Med. 2023 Mar 15;207(6):768-774. doi: 10.1164/rccm.202205-0963OC. PMID: 36383197.
        5. 
      
      5. Bhakta NR, Bime C, Kaminsky DA, McCormack MC, Thakur N, Stanojevic S, Baugh AD, Braun L, Lovinsky-Desir S, Adamson R, Witonsky J, Wise RA, Levy SD, Brown R, Forno E, Cohen RT, Johnson M, Balmes J, Mageto Y, Lee CT, Masekela R, Weiner DJ, Irvin CG, Swenson ER, Rosenfeld M, Schwartzstein RM, Agrawal A, Neptune E, Wisnivesky JP, Ortega VE, Burney P. Race and Ethnicity in Pulmonary Function Test Interpretation: An Official American Thoracic Society Statement. Am J Respir Crit Care Med. 2023 Apr 15;207(8):978-995. doi: 10.1164/rccm.202302-0310ST. PMID: 36973004; PMCID: PMC10112445.
        6. 
      
      6. Hall GL, Filipow N, Ruppel G, Okitika T, Thompson B, Kirkby J, Steenbruggen I, Cooper BG, Stanojevic S; contributing GLI Network members. Official ERS technical standard: Global Lung Function Initiative reference values for static lung volumes in individuals of European ancestry. Eur Respir J. 2021 Mar 11;57(3):2000289. doi: 10.1183/13993003.00289-2020. Print 2021 Mar. PMID: 33707167.
        7. 
      
      7. Stanojevic S, Graham BL, Cooper BG, Thompson BR, Carter KW, Francis RW, Hall GL; Global Lung Function Initiative TLCO working group. Official ERS technical standards: Global Lung Function Initiative reference values for the carbon monoxide transfer factor for Caucasians. Eur Respir J. 2017 Sep 11;50(3):1700010. doi: 10.1183/13993003.00010-2017. Print 2017 Sep. PMID: 28893868.
        8. 
      
      8. "Official ERS technical standards: Global Lung Function Initiative reference values for the carbon monoxide transfer factor for Caucasians." Sanja Stanojevic, Brian L. Graham, Brendan G. Cooper, Bruce R. Thompson, Kim W. Carter, Richard W. Francis and Graham L. Hall on behalf of the Global Lung Function Initiative TLCO working group. Eur Respir J 2017; 50: 1700010. Eur Respir J. 2020 Oct 15;56(4):1750010. doi: 10.1183/13993003.50010-2017. Print 2020 Oct. PMID: 33060163.
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      9. Graham BL, Brusasco V, Burgos F, Cooper BG, Jensen R, Kendrick A, MacIntyre NR, Thompson BR, Wanger J. 2017 ERS/ATS standards for single-breath carbon monoxide uptake in the lung. Eur Respir J. 2017 Jan 3;49(1):1600016. doi: 10.1183/13993003.00016-2016. Print 2017 Jan. PMID: 28049168.
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      10. Iyer VN, Schroeder DR, Parker KO, Hyatt RE, Scanlon PD. The nonspecific pulmonary function test: longitudinal follow-up and outcomes. Chest. 2011 Apr;139(4):878-886. doi: 10.1378/chest.10-0804. Epub 2010 Aug 19. PMID: 20724741.
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      11. Clay RD, Iyer VN, Reddy DR, Siontis B, Scanlon PD. The "Complex Restrictive" Pulmonary Function Pattern: Clinical and Radiologic Analysis of a Common but Previously Undescribed Restrictive Pattern. Chest. 2017 Dec;152(6):1258-1265. doi: 10.1016/j.chest.2017.07.009. Epub 2017 Jul 17. PMID: 28728932.
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      12. Wan ES, Castaldi PJ, Cho MH, Hokanson JE, Regan EA, Make BJ, Beaty TH, Han MK, Curtis JL, Curran-Everett D, Lynch DA, DeMeo DL, Crapo JD, Silverman EK; COPDGene Investigators. Epidemiology, genetics, and subtyping of preserved ratio impaired spirometry (PRISm) in COPDGene. Respir Res. 2014 Aug 6;15(1):89. doi: 10.1186/s12931-014-0089-y. PMID: 25096860; PMCID: PMC4256936.
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      13. Empey DW. Assessment of upper airways obstruction. Br Med J. 1972 Aug 26;3(5825):503-5. doi: 10.1136/bmj.3.5825.503. PMID: 5069620; PMCID: PMC1785761.
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