[ Education and Clinical Practice CHEST Reviews ]

Six-Minute Walk Test

Clinical Role, Technique, Coding, and Reimbursement
Priya Agarwala, MD; and Steve H. Salzman, MD

The 6-min walk test (6MWT) is a commonly used test for the objective assessment of functional
exercise capacity for the management of patients with moderate-to-severe pulmonary disease.
Unlike pulmonary function testing, the 6MWT captures the often coexisting extrapulmonary mani-
festations of chronic respiratory disease, including cardiovascular disease, frailty, sarcopenia, and
cancer. In contrast with cardiopulmonary exercise stress testing, this test does not require complex
equipment or technical expertise. In this low complexity, safe test, the patient is asked to walk as far
as possible along a 30-m minimally trafficked corridor for a period of 6 min with the primary
outcome measure being the 6-min walk distance (6MWD) measured in meters. There has been
interest in other derived indexes, such as distance-desaturation product (the product of nadir ox-
ygen saturation and walk distance), which in small studies has been predictive of morbidity and
mortality in certain chronic respiratory conditions. Special attention to methodology is required to
produce reliable and reproducible results. Factors that can affect walk distance include track layout
(continuous vs straight), track length, oxygen amount and portability, learning effect, and verbal
encouragement. The absolute 6MWD and change in 6MWD are predictive of morbidity and mortality
in patients with COPD, pulmonary arterial hypertension, and idiopathic pulmonary fibrosis and
patients awaiting lung transplant, highlighting its use in management decisions and clinical trials. As
of January 2018, Current Procedural Terminology code 94620 (simple pulmonary stress test) has
been deleted and replaced by two new codes, 94617 and 94618. Code 94617 includes exercise test
for bronchospasm including pre- and postspirometry, ECG recordings, and pulse oximetry. Code
94618, pulmonary stress testing (eg, 6MWT), includes the measurement of heart rate, oximetry,
and oxygen titration when performed. If 94620 is billed after January 2018 it will not be reimbursed.
CHEST 2020; 157(3):603-611

KEY WORDS: 6-min walk distance; 6-min walk test; COPD; current procedural terminology;
exercise pulse oximetry; fee schedule; idiopathic pulmonary fibrosis; physician
reimbursement; pulmonary hypertension

Pulmonary function tests have a central role rating severity in obstructive and restrictive
in patient management and research. FEV1 pulmonary diseases.1,2 However, correlations
has traditionally been recommended for of FEV1 with quality of life, mortality risk,

ABBREVIATIONS: 6MWD = 6-min walk distance; 6MWT = 6-min walk Clinical Excellence, Fire Department, City of New York (FDNY) (Dr
test; ATS = American Thoracic Society; CPET = cardiopulmonary Salzman), Brooklyn, NY.
exercise test; CPT = Current Procedural Terminology; DLCO = diffusing CORRESPONDENCE TO: Priya Agarwala, MD, Division of Pulmonary
capacity of the lung for carbon monoxide; DSP = distance-desaturation and Critical Care Medicine, NYU Winthrop Hospital, 222 Station
product; E/M = evaluation and management; HR = hazard ratio; IPF = Plaza N, Mineola, NY 11501; e-mail: priya.agarwala@nyulangone.org
idiopathic pulmonary fibrosis; PAH = pulmonary arterial hyperten- Copyright Ó 2019 American College of Chest Physicians. Published by
sion; SpO2 = oxygen saturation measured by pulse oximetry Elsevier Inc. All rights reserved.
AFFILIATIONS: From the Division of Pulmonary and Critical Care
DOI: https://doi.org/10.1016/j.chest.2019.10.014
Medicine (Drs Agarwala and Salzman), NYU Winthrop Hospital,
Mineola, NY; and World Trade Center Health Program Center of

chestjournal.org 603
and functional status are only moderate.3,4 It is likely turns.18 Treadmills offer the advantage of compact space
this single parameter does not capture the often requirements and easy continuous monitoring, but
coexisting extrapulmonary manifestations of chronic unfamiliarity with the machinery can lead to significantly
respiratory disease, including cardiovascular disease, lower walk distance.19,20 Table 2 provides a summary of
frailty, sarcopenia, and cancer, which contribute to procedural guidelines.10,11,15,18,21-23
morbidity and mortality.5,6 This has led to interest in
Verbal encouragement is commonly used to enhance
broader measures of functional capacity. Peak oxygen
participation. Careful attention should be given to the
uptake obtained from cardiopulmonary exercise testing
language used to instruct the patient and the frequency
(CPET) has proven to be a better predictor of mortality
of encouragement. The scripted instructions in the
and health-care related quality of life than FEV1.7
guidelines state “the object of this test is to walk as far as
Unfortunately, obtaining this measurement requires
possible for 6 minutes.”10 In a study of patients with
complex equipment and technical expertise.
idiopathic pulmonary fibrosis (IPF), interstitial lung
Additionally, patients with advanced disease are often
disease, and pulmonary arterial hypertension (PAH),
unable to perform CPET because of severe functional
focus on speed by instructing them to “walk as fast as
limitation.8,9
you can” led to a considerable increase in 6MWD.24
The 6-min walk test (6MWT) is a commonly used test Nevertheless, it is recommended against use of this
for the objective assessment of functional exercise phrase because the initial benefit of increased speed may
capacity for the management of patients with moderate- be offset by fatigue experienced later and may place
to-severe pulmonary disease. In this relatively low undue stress on patients with cardiac conditions.11 The
complexity test, the patient is asked to walk as far as guidelines provide standardized encouragement phrases
possible along a 30-m corridor for a period of 6 min to be delivered exclusively at 1-min intervals because
with the primary outcome measure being 6-min walk frequency of encouragement can also affect walk
distance (6MWD).10 distance.11,23
Changes in 6MWD and other derived measurements Two tests should be performed given the learning
can be used to determine treatment response and predict effect. The most robust data originate from patients
morbidity and mortality in chronic respiratory with COPD; however, limited data in other respiratory
diseases.10 Relative and absolute contraindications diseases suggest the same.25,26 The largest retrospective
and the specific indications for 6MWT are outlined observational study including 1,514 patients with
in Table 1. COPD performing the 6MWT on subsequent days
found an average increase in 6MWD of 27 m, with
Test Procedure most experiencing an improvement on the second
walk.27 Performing tests on subsequent days is not
The American Thoracic Society (ATS) published
practical in clinical settings. A suggested best of two
guidelines11 for the 6MWT in 2002 with a subsequent
approach may balance underperformance on the initial
joint European Respiratory Society and ATS updated
test in those lacking familiarity and underperformance
systematic review18 and technical standard10 in 2014.
on the subsequent test from fatigue.28
A brief summary is outlined here.
Standardized 6MWT methodology is essential for Safety Considerations
reproducible and reliable results. The test should be
The 6MWT is a safe test with rare complications
performed in a minimally trafficked area along a flat,
(Table 2). In a large study of outpatients with COPD or
straight corridor ideally $ 30 m in length to be consistent
interstitial lung disease performing the test in
with established reference equations.11 There are reference
pulmonary rehabilitation, the most common adverse
equations for shorter tracks, including 20 m12 and 10 m13
event was oxygen desaturation # 80% in 5% of testing.
to reflect space limitations in practice.14 Both track length
Patient symptoms prematurely terminated the test in
and layout affect walk distance. For example, in a
1% of testing.22
crossover study of patients with COPD, a track length of
30 m resulted in significantly greater walk distance in
comparison with 10 m.15 Continuous tracks in either Novel Indexes
square, circular, or oval layouts resulted in greater walk There has been interest in other derived indexes with
distances,16,17 reflecting the time required to make abrupt prognostic implications. The distance-desaturation

604 CHEST Reviews [ 157#3 CHEST MARCH 2020 ]

TABLE 1 ] Indications and Contraindications for TABLE 1 ] (Continued)
Performing the 6-Min Walk Test
High degree atrioventricular block
Indications10 Hypertrophic cardiomyopathy
Response to a medical intervention (pretreatment and Significant pulmonary hypertension
posttreatment comparisons)
Advanced or complicated pregnancy
Lung transplantation
Electrolyte abnormalities
Lung resection
Orthopedic impairment that prevents walking
Lung volume reduction surgery
Pulmonary rehabilitation SpO2 ¼ oxygen saturation measured by pulse oximetry.

COPD
Pulmonary arterial hypertension product (DSP) is defined as the product of nadir oxygen
Congestive heart failure saturation measured by pulse oximetry (SpO2) on room
Single measurement of functional status air and 6MWD in meters, easily calculated with
COPD
continuous pulse oximetry (expressed as meters-
Cystic fibrosis
percent [m%]).18 In a prospective longitudinal study
assessing clinical outcomes of patients with COPD, a
Congestive heart failure
DSP # 290 m% better predicted mortality than
Peripheral vascular disease
6MWD # 334 m or SpO2 # 88% after adjusting for age,
Fibromyalgia
sex, BMI, FEV1, FEV1 to FVC ratio, St. George’s
Predictors of morbidity and mortality
Respiratory Questionnaire, emphysema, and
Congestive heart failure
smoking.29 Similarly, in a cohort of patients with IPF,
COPD
DSP < 200 m% was associated with a 6.5-fold greater
Idiopathic pulmonary arterial hypertension
mortality and performed better as a screening tool for
Idiopathic pulmonary fibrosis 12-month mortality than either 6MWD or percent
Absolute contraindications10 nadir desaturation alone.30
Acute myocardial infarction (3-5 d)
A more complex and less widely used index, the
Unstable angina
desaturation area, defined as the total area above the
Uncontrolled arrhythmias causing symptoms or
hemodynamic compromise curve between SpO2 observed at every minute during
Syncope the 6MWT and 100% has been studied in patients with
Acute endocarditis
IPF, showing an increased hazard ratio (HR) for
Acute myocarditis or pericarditis
mortality for every 10-point increase in the
desaturation area.18,31
Symptomatic severe aortic stenosis
Uncontrolled heart failure The 6-min walk work is the product of 6MWD and body
Acute pulmonary embolism or pulmonary infarction weight, which may better reflect the amount of energy
Thrombosis of lower extremities required to complete the test.18 Studies in patients with
Suspected dissecting aneurysm COPD have evaluated its correlation with physiological
Uncontrolled asthma measures of exercise. It correlates more strongly to peak
Pulmonary edema oxygen uptake than 6MWD.32,33
Room air SpO2 # 85%
Acute respiratory failure Interpretation of Change in 6MWD
Acute noncardiopulmonary disorder that may affect Change over time in 6MWD can be expressed as
exercise performance or be aggravated by exercise absolute difference in meters, percentage change,
Mental impairment preventing cooperation with or change in percent predicted. See Table 3
examination for details.11,34,35
Relative contraindications10
Current Clinical Use of the 6MWT
Left main coronary stenosis or its equivalent
Moderate stenotic valvular disease COPD
Untreated hypertension at rest (200 mm Hg systolic, There is a strong correlation between 6MWD and
180 mm Hg diastolic)
clinical outcomes in COPD, likely because 6MWD
(Continued) captures both the pulmonary and extrapulmonary

chestjournal.org 605
TABLE 2 ] Procedural Guidelines
Mark the starting line with brightly colored tape11
Mark the length of the hallway every 3 m11
Mark turn around points with a cone11
Patients should be wearing comfortable clothing and use their usual walking aids11
Patient should be using their prescribed oxygen therapy and manage their oxygen delivery device. If this is not possible,
assessor is to walk slightly behind to avoid setting the pace10,18
Notation should be made of how patient was assisted with oxygen because subsequent tests should be performed in the
same fashion10,18
Oxygen should not be titrated during the study because supplemental oxygen and its portability affect exercise performance
and walk distance11
The patient should rest for at least 10 min prior to commencement of testing11
During this time, BP, heart rate, SpO2, and baseline dyspnea and fatigue should be documented11
Continuous SpO2 should be monitored to capture nadir SpO2, which does not always correlate with end test SpO210,21
If the patient stops during testing, the timer should not be stopped. The time at which the patient stopped and recommenced
walking should be noted11
Reasons for premature cessation of testing by the patient include symptoms of chest pain, intolerable dyspnea, or leg pain11
Assessor may terminate testing based on appearance of the patient or if oxygen saturation falls < 80%22
Walk distance is measured by counting the number of full laps and rounding to the nearest meter for the partial final lap11,18
At test cessation, the parameters measured during the pretesting period are repeated11,18
Safety considerations include the following:
 Technician or other testing providers should be certified in basic life support and cardiopulmonary resuscitation
 Access to emergency equipment including a crash cart and medications including sublingual nitrogen, aspirin, and
bronchodilators15,23

See Table 1 legend for expansion of abbreviation.

manifestations of the disease. In fact, comorbid updated BODE Index which assigns greater weight to
conditions likely account for > 50% of deaths in the 6MWD more accurately predicted mortality than
patients with COPD.5 Consequently, the inclusion of the original scoring system.36
6MWD with FEV1, dyspnea, and BMI is a better
predictor of mortality than FEV1 alone. The BODE A study of longitudinal changes in 6MWD in 198
Index is a 10-point scale in which higher scores patients with severe COPD over a 2-year period found
indicate a greater risk of death. The 6MWD is given improved survival with increases in 6MWD when
0 points for > 350 m, 1 point for 250 to 349 m, 2 divided into discrete 100-m increments. Additionally,
points for 150 to 249 m, and 3 points for # 149 m. nonsurvivors had a significant decline in 6MWD
Each one-point increment in the BODE Index of 40 m compared with 22 m for survivors over 1
increases the HR for death from any cause by 1.4 An year without a parallel change in FEV1. The rate of

TABLE 3 ] Interpretation of Change in 6-Min Walk Distance

 Can be expressed as absolute difference in meters, percentage change, or change in percent predicted.
 ATS recommends change be expressed in terms of absolute value.11
 MID used because statistically significant change may not have clinical relevance.
 MID is smallest change in 6-min walk distance that is perceived to be important enough to prompt modification in
management by the physician.34
 Most studies use statistical distribution-based methods to determine this difference rather than anchor-based methods,
which incorporates the patient’s perspective on change.35
 In a study of patients with COPD who completed a 6-min walk test before and after a 7-wk rehabilitation program, a MID of
25 m was identified when using the anchor of patient’s perceived change in walk ability. This anchor-based method
demonstrated excellent agreement with distribution-based calculation of MID.34

MID ¼ minimal important difference

606 CHEST Reviews [ 157#3 CHEST MARCH 2020 ]

TABLE 4 ] Medicare Reimbursement for 6MWT and Related Exercise Tests, Year 2018a
CPT Code Region Global Fee Technical Fee Professional Fee
94617: exercise test for New York City Metro $114.69 $76.59 $38.10
bronchospasm
Indiana $90.39 $57.51 $32.89
Kentucky $88.45 $55.40 $33.05
94618: pulmonary stress New York City Metro $40.26 $14.22 $26.04
testing (eg, 6MWT)
Indiana $32.91 $10.39 $22.52
Kentucky $32.74 $10.12 $22.62
94621: cardiopulmonary New York City Metro $197.35 $118.67 $78.68
exercise testing
Indiana $157.42 $89.60 $67.82
Kentucky $154.22 $86.12 $68.09

Fee schedule comes from the Centers for Medicare and Medicaid Services.64 6MWT ¼ 6-min walk test; CPT ¼ Current Procedural Terminology; New York
City Metro ¼ New York City boroughs of the Bronx, Brooklyn, and Staten Island and the neighboring suburban counties of Nassau, Suffolk, Westchester, and
Rockland.
a
Fee schedule rates are in dollars for physicians participating in the Medicare program.

decline in 6MWD between survivors and nonsurvivors of patients newly diagnosed with IPF, 6MWD #
was significantly different; however, FEV1 was not. The 72% predicted was a significant independent predictor of
authors concluded that although FEV1 is useful in mortality with an HR of 3.27. When added to a
stratifying patients by disease severity, in patients with composite physiological index (calculated based on
severe COPD, 6MWD may be a better predictor of extent of disease on CT scan, diffusing capacity of the
mortality.37 lung for carbon monoxide [DLCO], FVC, and FEV1)42
and Medical Research Council dyspnea scale score, it
In a prospective observational study of 2,110 patients
was able to predict 3-year mortality with
with clinically stable Global Initiative for Chronic
100% specificity.43 Data from the effect of interferon
Obstructive Lung Disease stage II to IV COPD where
gamma-1b on survival in patients with idiopathic
baseline and yearly 6MWTs were conducted, the 6MWD
pulmonary fibrosis (INSPIRE) clinical trial examining
thresholds with the highest sensitivity and specificity for
the role of interferon gamma-1b found that a 6MWD <
hospitalization or 3-year mortality were 357 and 334 m,
250 m was associated with a twofold increase in
respectively. Note, however, these thresholds pertained
mortality at 1 year, and a decline in walk distance by >
to the group as a whole and when stratified by age, these
50 m at 24 weeks was associated with close to threefold
thresholds changed greatly.38 Nevertheless, these values
increase in mortality at 1 year.44 A retrospective analysis
are consistent with a large meta-analysis revealing a
of patients randomized to the placebo arm of
discriminatory value of 350 m below which the risk of
pirfenidone found similar results; however, these were
death and hospitalization increased quasilinearly.39
not statistically significant.45 These findings highlight
IPF the use of the 6MWT as a surrogate marker for mortality
in clinical trials.
The variable clinical course that is characteristic of IPF
has led to interest in reliable and independent predictors Other variables measured during testing have prognostic
of disease outcome. In patients with fibrotic lung implications in IPF. For example, heart rate recovery < 13
diseases, the 6MWT is more reproducible than CPET beats/min after cessation of testing is associated with a
and correlates strongly with the maximum rate of more than fivefold risk of death.46 Heart rate recovery is
oxygen consumption measured during incremental also a predictor of the presence of pulmonary hypertension
exercise at maximum exercise intensity (V_ O2 max).40 as measured via right-sided heart catheterization in patients
Additionally, its simplicity likely results in greater with IPF.47 Oxygen desaturation < 88% is also associated
patient acceptance. The 6MWT has been a useful with significant mortality risk (HR, 4.47), even when
predictor of outcomes in numerous clinical settings in adjusting for other physiological variables, including DLCO,
patients with IPF.41 In a prospective observational study FVC, and resting saturation.48

chestjournal.org 607
Lung Transplant 6MWD at baseline.55,56 A large meta-analysis of 16
Prior to 2005, allocation of lungs was largely dependent randomized controlled trials in PAH including nearly
on wait-list times, regardless of disease severity.49 This 2,000 patients confirmed the association between
led many physicians to prematurely place patients on 6MWD at baseline and mortality, particularly when the
the transplant list to accrue time. Under this system, 6MWD was < 330 m.57 Absolute 6MWD reached after
wait-list time was > 2 years and mortality was therapy has also been shown to predict survival. In a
10% while awaiting transplantation.50 In 1995, to French cohort of patients with World Health
account for higher mortality rates in candidates with Organization class III or IV PAH treated with 4 months
IPF, 90 days of wait time was granted at listing. In 2005, of bosentan, those who achieved a posttreatment
a new allocation system was implemented to improve 6MWD > 378 vs < 378 m had improved survival at 1, 2,
equitable distribution of organs.51 The lung allocation and 3 years.58 Unfortunately, no single absolute
score is a 0 to 100 scale using criteria predictive of both threshold value has been validated in the literature;
wait-list and posttransplant mortality. 6MWD has been therefore, a specific target threshold to gauge treatment
incorporated into the scoring system as a dichotomous benefit is unknown. In addition, several systematic
variable (above or below 150 ft [45.7 m]).49 Controversy reviews and meta-analyses of randomized trials have
exists regarding the appropriate threshold, or if use as a failed to show a survival benefit with improvement in
continuous variable is preferable.50 6MWD.59 These data call into question the usefulness of
improvement in 6MWD as a surrogate marker for
The International Society for Heart and Lung clinical outcomes and stress the need for alternative end
Transplantation guidelines uses disease-specific points that better represent clinical benefits. The
considerations for lung transplant referrals and listing. European Cardiology Society and European Respiratory
For IPF, referral is recommended for abnormal lung Society guidelines60 for diagnosis and treatment of
function defined by DLCO and FVC, functional pulmonary hypertension still suggest obtaining 6MWT
limitation, or need for supplemental oxygen. Criteria for at baseline, and then every 3 to 6 months after initiation
listing include desaturation < 88% on 6MWT, of treatment.60
6MWD < 250 m, or a decline by > 50 m in 6 months.
For those with COPD, the BODE Index, which includes
6MWD, should be used in determining optimal timing Coding and Billing
for both referral and listing.52 The American Medical Association61 has developed the
Current Procedural Terminology (CPT), which consists
PAH of identifying codes for uniform reporting of medical
The first randomized controlled drug trial for PAH- services and procedures. The CPT consists of five digits
specific therapy, published in 1996, used 6MWD as the to identify the procedure with optional addition of two-
primary outcome.53 Interestingly, this was chosen by the digit modifiers.61 Medicare and other payers recognize
sponsor as a compromise to the Food and Drug two components to most diagnostic tests, including
Administration’s requirement that the primary end pulmonary function and exercise testing. The
point be a measure of patient symptoms, exercise professional component consists of the interpretation of
capacity, or survival. Survival as an end point required a the test and the report subsequently generated by the
longer study, and World Health Organization functional physician, identified by a 26 modifier to the five-digit
class was deemed too subjective; therefore, 6MWD was procedural code. The technical component which
used as an objective end point.54 The increase in 6MWD captures the expenses related to the performance of the
seen in this study led the way for future PAH studies. test, including the cost of technicians, equipment, and
However, there has been much debate regarding the space, is indicated by the technical component (TC)
prognostic value of 6MWD in PAH. modifier. The global service, which includes both the
professional and technical components, is identified by
Treatment studies have examined three 6MWD the five-digit code alone. This code should be used when
parameters, including 6MWD at treatment initiation, the physician who performs the professional component
6MWD posttreatment, and the pre- to posttreatment is used by the entity that performs the technical
change in 6MWD.53 In clinical trials of epoprostenol, component or when a self-employed physician
and epoprostenol with add-on sildenafil therapy, interprets the test but also owns or leases the equipment
subjects who died had a significantly lower mean and pays the technician.62

608 CHEST Reviews [ 157#3 CHEST MARCH 2020 ]

Prior to January 2018, the 6MWT was reported under codes for the CPT code and E/M code, if appropriate, may
a simple pulmonary stress test code (94620). Under help to delineate this medical necessity.62
this code, other types of exertional testing could also
be reported including oxygen titration with oximetry, Conclusions
excised-induced bronchospasm with pre- and
The 6MWT has emerged as a reliable measure of
postexercise spirometry, or exercise prescription for
functional capacity that is simple to perform and
pulmonary rehabilitation. The technical performance
interpret. The test, however, is extremely sensitive to
of the test and the interpretation of the data were
methodology; therefore, a standardized approach is
included within the code (94620). Significant
crucial. Careful attention must be given to track layout
documentation to support the use of code 94620 was
and length, oxygen therapy, and portability, in addition
required including, but not limited to, total distance
to strict adherence to protocols of instruction, verbal
walked, interpretation, recommendations, and data
encouragement, and measurements before and after
collected during the testing including heart rate, BP,
testing. The primary outcome measure, 6MWD, has
and oxygen saturation. Although it was recognized
been studied as a predictor of mortality across a wide
that spirometry is often performed at baseline and
range of chronic respiratory conditions, including
after exercise, this was not an essential requirement to
COPD, IPF, and PAH, and wait-list mortality for lung
use the global service code of 94620.62
transplant. Significant changes from previous ATS
The CPT codes as of January 2018 have since been guidelines include the recommendation of continuous
revised. The code 94620 has been eliminated, and two SpO2 monitoring during testing and the performance of
additional codes (94617 and 94618) have been added. two tests given the clear learning effect. Previous CPT
The American Medical Association Relativity code of 94620 is no longer valid for billing of 6MWT
Assessment Workgroup,63 which works to identify and will not be reimbursed if billed under this code after
potentially misvalued services, determined that the two January 1, 2018. Rather, 6MWT is appropriately coded
tests falling under 94620, including 6MWT and pre- and under 94618 with significant documentation required
postexercise oximetry, were describing two completely beyond 6MWD and SpO2.
different examinations. For this reason, two codes were
added to better delineate the different examinations Acknowledgments
formerly housed under 94620. Code 94617 reflects Financial/nonfinancial disclosures: The authors have reported to
CHEST the following: P. A. and S. H. S. receive NIH grant [No.
exercise test for bronchospasm including pre- and NCT02634268], which pays money to their institution, but is not
postspirometry, ECG recordings, and pulse oximetry. directly related to this study.
Code 94618 only encompasses pulmonary stress testing
(eg, 6MWT) including measurement of heart rate, References
oximetry, and oxygen titration when performed. Code 1. Pelligrino R, Viegi G, Brusasco V, et al. Series: ATS/ERS task force:
standardisation of lung function testing: interpretative strategies for
94621 remains unchanged to describe cardiopulmonary lung function tests. Eur Respir J. 2005;26(5):948-968.
exercise testing, including measurements of minute 2. Pauwels R, Anthonisen N, Bailey WC, et al. Global Initiative for
Chronic Obstructive Lung Disease. Global strategy for the diagnosis,
ventilation, CO2 production, oxygen uptake, and ECG management and prevention of chronic obstructive pulmonary
recordings. Note that the term “simple” has been disease. NHLBI/WHO workshop report. Bethesda, MD: National
Heart, Lung and Blood Institute; 2001:1-100. NIH Publication No.
removed from the nomenclature. If CPT code 94620 is 2701.
used after January 1, 2018, the claim will be denied.61 3. Patel SA, Sciurba FC. Emerging concepts in outcome assessment for
Table 4 lists Medicare reimbursement for 6MWT and COPD clinical trials. Sem Respir Crit Care Med. 2005;26(2):253-262.
related exercise tests.64 4. Celli BR, Cote CG, Marin JM, et al. The body-mass index, airflow
obstruction, dyspnea, and exercise capacity index in chronic
When a diagnostic test is performed on the same day as an obstructive pulmonary disease. N Engl J Med. 2004;350(10):1005-
1012.
evaluation and management (E/M) service (new patient
5. Celli BR, Cote CG, Lareau SC, Meek PM. Predictors of Survival in
visit, consultation, or subsequent visit), the addition of a COPD: more than just the FEV1. Respir Med. 2008;102(suppl 1):
25 modifier (ie, “a separately identifiable E/M service on S27-S35.

the same calendar day by the same physician”62) should be 6. Gale NS, Albarrati AM, Munnery MM, et al. Frailty: a global measure
of the multisystem impact of COPD. Chron Respir Dis. 2018;15(4):347-
used when an E/M service is also billed. There must be 355.
reasonable medical necessity to report an E/M code with a 7. Oga T, Nishimura K, Tsukino M, Sato S, Hajiro T. Analysis of the
factors related to mortality in chronic obstructive pulmonary
procedural code together. Designating separate disease: role of exercise capacity and health status. Am J Respir Crit
International Classification of Diseases, Tenth Revision Care Med. 2003;167(4):544-549.

chestjournal.org 609
 8. Cote CG, Pinto-Plata V, Kasprzyk K, Dordelly LJ, Celli BR. The 6- 29. Andrianopoulos V, Wouters EF, Pinto-Plata VM, et al. Prognostic
min walk distance, peak oxygen uptake, and mortality in COPD. value of variables derived from the six-minute walk test in patients
Chest. 2007;132(6):1778-1785. with COPD: results from the ECLIPSE study. Respir Med.
2015;109(9):1138-1146.
9. Epstein SK, Faling LJ, Daly BD, Celli BR. Inability to perform bicycle
ergometry predicts increased morbidity and mortality after lung 30. Lettieri CJ, Nathan SD, Browning RF, Barnett SD, Ahmad S,
resection. Chest. 1995;107(2):311-316. Shorr AF. The distance-saturation product predicts mortality in
10. Holland AE, Spruit MA, Troosters T, et al. An official European idiopathic pulmonary fibrosis. Respir Med. 2006;100(10):1734-1741.
Respiratory Society/American Thoracic Society technical standard: 31. Flaherty KR, Andrei AC, Murray S, et al. Idiopathic pulmonary
field walking tests in chronic respiratory disease. Eur Respir J. fibrosis: prognostic value of changes in physiology and six-minute-
2014;44(6):1428-1446. walk test. Am J Respir Crit Care Med. 2006;174(7):803-809.
11. ATS Committee on Proficiency Standards for Clinical Pulmonary 32. Chuang ML, Lin IF, Wasserman K. The body weight-walking
Function Laboratories. ATS statement: guidelines for the six- distance product as related to lung function, anaerobic threshold and
minute walk test. Am J Respir Crit Care Med. 2002;166(1): peak VO2 in COPD patients. Respir Med. 2001;95(7):618-626.
111-117.
33. Poersch K, Berton DC, Canterle DB, et al. Six-minute walk distance
12. Gibbons WJ, Fruchter N, Sloan S, Levy RD. Reference values for a and work relationship with incremental treadmill cardiopulmonary
multiple repetition 6-minute walk test in healthy adults older than exercise test in COPD. Clin Respir J. 2013;7(2):145-152.
20 years. J Cardiopulm Rehabil. 2001;21(2):87-93.
34. Holland AE, Hill CJ, Rasekaba T, Lee A, Naughton MT,
13. Beekman E, Mesters I, Gosselink R, et al. The first reference McDonald CF. Updating the minimal important difference for six-
equations for the 6-minute walk distance over a 10 m course. minute walk distance in patients with chronic obstructive pulmonary
Thorax. 2014;69(9):867-868. disease. Arch Phys Med Rehabil. 2010;91:221-225.
14. Beekman E, Mesters I, Gosselink R, van Schayck OC, de Bie RA. 35. King MT. A point of minimal important difference (MID): a critique
Authors’ response: What determines which 6MWT is conventional? of terminology and methods. Expert Rev Pharmacoecon Outcomes
Thorax. 2015;70(1):86-87. Res. 2011;11(2):171-184.
15. Beekman E, Mesters I, Hendriks EJ, et al. Course length of 30 metres 36. Puhan MA, Garcia-Aymerich J, Frey M, et al. Expansion of the
versus 10 metres has a significant influence on six-minute walk prognostic assessment of patients with chronic obstructive
distance in patients with COPD: an experimental crossover study. pulmonary disease: the updated BODE index and the ADO index.
J Physiother. 2013;59(3):169-176. Lancet. 2009;374(9691):704-711.
16. Sciurba F, Criner GJ, Lee SM, et al. Six-minute walk distance in 37. Pinto-Plata VM, Cote C, Cabral H, Taylor J, Celli BR. The 6-min
chronic obstructive pulmonary disease: reproducibility and effect of walk distance: change over time and value as a predictor of survival
walking course layout and length. Am J Respir Crit Care Med. in severe COPD. Eur Respir J. 2004;23(1):28-33.
2003;167(11):1522-1527.
38. Spruit MA, Polkey MI, Celli B, et al. Predicting outcomes from 6-
17. Bansal V, Hill K, Dolmage TE, Brooks D, Woon LJ, Goldstein RS. minute walk distance in chronic obstructive pulmonary disease.
Modifying track layout from straight to circular has a modest effect J Am Med Dir Assoc. 2012;13(3):291-297.
on the 6-min walk distance. Chest. 2008;133(5):1155-1160.
39. Celli B, Tetzlaff K, Criner G, et al. The 6-minute-walk distance test as
18. Singh SJ, Puhan MA, Andrianopoulos V, et al. An official systematic
a chronic obstructive pulmonary disease stratification tool. Insights
review of the European Respiratory Society/American Thoracic
from the COPD Biomarker Qualification Consortium. Am J Respir
Society: measurement properties of field walking tests in chronic
Crit Care Med. 2016;194(12):1483-1493.
respiratory disease. Eur Respir J. 2014;44(6):1447-1478.
40. Eaton T, Young P, Milne D, Wells AU. Six-minute walk, maximal
19. Stevens D, Elpern E, Sharma K, et al. Comparison of hallway and
exercise tests: reproducibility in fibrotic interstitial pneumonia. Am J
treadmill six-minute walk tests. Am J Respir Crit Care Med.
Respir Crit Care Med. 2005;171(10):1150-1157.
1999;160(5 pt 1):1540-1543.
20. de Almeida FG, Victor EG, Rizzo JA. Hallway versus treadmill 6- 41. Brown AW, Nathan SD. The value and application of the 6-minute-
minute-walk tests in patients with chronic obstructive pulmonary walk test in idiopathic pulmonary fibrosis. Ann Am Thorac Soc.
disease. Respir Care. 2009;54(12):1712-1716. 2018;15(1):3-10.

21. Fiore C, Lee A, McDonald C, Hill C, Holland A. Should 42. Wells AU, Desai SR, Rubens MB, et al. Idiopathic pulmonary
oxyhaemoglobin saturation be monitored continuously during the 6- fibrosis: a composite physiologic index derived from disease extent
minute walk test? Chron Respir Dis. 2011;8(3):181-184. observed by computed tomography. Am J Respir Crit Care Med.
2003;167(7):962-969.
 cins N. Six-minute walk test: observed adverse events
22. Jenkins S, Ce
and oxygen desaturation in a large cohort of patients with chronic 43. Mura M, Porretta MA, Bargagli E, et al. Predicting survival in newly
lung disease. Intern Med J. 2011;41(5):416-422. diagnosed idiopathic pulmonary fibrosis: a 3-year prospective study.
Eur Respir J. 2012;40(1):101-109.
23. Guyatt GH, Pugsley SO, Sullivan MJ, et al. Effect of encouragement
on walking test performance. Thorax. 1984;39(11):818-822. 44. du Bois RM, Albera C, Bradford WZ, et al. 6-Minute walk distance is
an independent predictor of mortality in patients with idiopathic
24. Weir NA, Brown AW, Shlobin OA, et al. The influence of alternative pulmonary fibrosis. Eur Respir J. 2014;43(5):1421-1429.
instruction on 6-min walk test distance. Chest. 2013;144(6):1900-
1905. 45. Nathan SD, du Bois RM, Albera C, et al. Validation of test
performance characteristics and minimal clinically important
25. Jenkins S, Cecins NM. Six-minute walk test in pulmonary difference of the 6-minute walk test in patients with idiopathic
rehabilitation: do all patients need a practice test? Respirology. pulmonary fibrosis. Respir Med. 2015;109(7):914-922.
2010;15(8):1192-1196.
46. Swigris JJ, Swick J, Wamboldt FS, et al. Heart rate recovery after 6-
26. Spencer L, Zafiropoulos B, Denniss W, Fowler D, Alison J, min walk test predicts survival in patients with idiopathic pulmonary
Celermajer D. Is there a learning effect when the 6-minute walk test fibrosis. Chest. 2009;136(3):841-848.
is repeated in people with suspected pulmonary hypertension?
Chron Respir Dis. 2018;15(4):339-346. 47. Swigris JJ, Olson AL, Shlobin OA, Ahmad S, Brown KK, Nathan SD.
Heart rate recovery after six-minute walk test predicts pulmonary
27. Hernandes NA, Wouters EF, Meijer K, Annegarn J, Pitta F, hypertension in patients with idiopathic pulmonary fibrosis.
Spruit MA. Reproducibility of 6-minute walking test in patients with Respirology. 2011;16(3):439-445.
COPD. Eur Respir J. 2011;38(2):261-267.
48. Lama VN, Flaherty KR, Toews GB, et al. Prognostic value of
28. Chandra D, Kulkarni HS, Sciurba F. Learning from the learning desaturation during a 6-minute walk test in idiopathic interstitial
effect in the six-minute-walk test. Am J Respir Crit Care Med. pneumonia. Am J Respir Crit Care Med. 2003;168(9):1084-1090.
2012;185(6):684.

610 CHEST Reviews [ 157#3 CHEST MARCH 2020 ]

49. Egan TM, Murray S, Bustami RT, et al. Development of the new lung 57. Macchia A, Marchioli R, Marfisi R, et al. A meta-analysis of
allocation system in the United States. Am J Transplant. 2006;6(5 Pt trials of pulmonary hypertension: a clinical condition looking for
2):1212-1227. drugs and research methodology. Am Heart J. 2007;153(6):1037-
50. Castleberry A, Mulvihill MS, Yerokun BA, et al. The utility of 6- 1047.
minute walk distance in predicting waitlist mortality for lung 58. Provencher S, Sitbon O, Humbert M, Cabrol S, Jaïs X,
transplant candidates. J Heart Lung Transplant. 2017;36(7):780-786. Simonneau G. Long-term outcome with first-line bosentan
51. Eberlein M, Garrity ER, Orens JB. Lung allocation in the United therapy in idiopathic pulmonary arterial hypertension. Eur Heart
States. Clin Chest Med. 2011;32(2):213-222. J. 2006;27(5):589-595.
52. Weill D, Benden C, Corris PA, et al. A consensus document for the 59. Souza R, Channick RN, Delcroix M, et al. Association between six-
selection of lung transplant candidates: 2014–an update from the minute walk distance and long-term outcomes in patients with
Pulmonary Transplantation Council of the International Society for pulmonary arterial hypertension: data from the randomized
Heart and Lung Transplantation. J Heart Lung Transplant. SERAPHIN trial. PLoS One. 2018;13(3):e0193226.
2015;34(1):1-15. 60. Galiè N, Humbert M, Vachiery JL, et al. 2015 ESC/ERS guidelines for
53. Gaine S, Simonneau G. The need to move from 6-minute walk the diagnosis and treatment of pulmonary hypertension. Eur Respir
distance to outcome trials in pulmonary arterial hypertension. Eur J. 2015;46(6):1855-1856.
Respir Rev. 2013;22(130):487-494.
61. CPT 2018 Changes: An Insider’s View. Chicago, IL: American
54. Rich S. The 6-minute walk test as a primary endpoint in clinical Medical Association; 2018.
trials for pulmonary hypertension. J Am Coll Cardiol. 2012;60(13):
1202-1203. 62. Diamond E. Pulmonary function and exercise testing. In: Manaker S,
ed. Coding for Chest Medicine. 17th ed. Glenview, IL: American
55. Barst RJ, Rubin LJ, Long WA, et al. A comparison of continuous College of Chest Physicians; 2016:141-158.
intravenous epoprostenol (prostacyclin) with conventional therapy
for primary pulmonary hypertension. N Engl J Med. 1996;334(5): 63. The RUC Relativity Assessment Workgroup Progress Report.
296-301. https://www.ama-assn.org/sites/default/files/media-browser/public/
rbrvs/raw-progress-report-updated.pdf.
56. Simonneau G, Rubin LJ, Galiè N, et al. Long-term sildenafil
added to intravenous epoprostenol in patients with pulmonary 64. Centers for Medicare and Medicaid Services. Physician fee schedule
arterial hypertension. J Heart Lung Transplant. 2014;33(7): search. https://www.cms.gov/apps/physician-fee-schedule/search/
689-697. search-criteria.aspx. Accessed January 15, 2019.

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