I was contacted recently by an individual with some questions about the pulmonary function testing needed for a Social Security Disability evaluation. With a small amount of research I was able to answer their questions but this brought up an interesting point and that is that despite the number of patients we see every year my lab only rarely performs any pulmonary function testing for disability evaluations. The reason I know this is because the Social Security Administration (SSA) has very specific requirements for the content and form of pulmonary function reports and we are very rarely asked for these reports.

The pulmonary function tests the SSA uses as part of a disability evaluation are:

• Spirometry
• Diffusing Capacity (DLCO)
• ABG
• Pulse Oximetry

Interestingly, lung volume measurements are not included. This is not specifically explained but it appears to be because evaluation for restriction is covered by the criteria for FVC and FEV1.

For all pulmonary function tests the SSA requires that the individual be medically stable, which they define as not:

• Within 2 weeks of a change in prescribed respiratory medication.
• Experiencing, or within 30 days of completion of treatment for, a lower respiratory tract infection.
• Experiencing, or within 30 days of completion of treatment for, an acute exacerbation of a chronic respiratory disorder.
• Hospitalized, or within 30 days of a hospital discharge, for an acute myocardial infarction (heart attack).

The performance and quality criteria for spirometry and diffusing capacity are essentially identical to the ATS/ERS standards. For spirometry, there needs to be three acceptable tests and acceptable is defined as:

“maximum effort following a full inspiration, and when the test tracing has a sharp takeoff and rapid rise to peak flow, has a smooth contour, and either lasts for at least 6 seconds or maintains a plateau for at least 1 second.“

Spirometry results are evaluated using the largest FVC and FEV1. There are no published requirements for repeatability but I strongly suspect that any reviewer presented with poorly reproducible results would consider this an indication that the person in question is not giving their best effort.

SSA requires post-bronchodilator spirometry if the FEV1 is less than 70% of predicted but does not specify which reference equations are used for this purpose nor does it specify which bronchodilator should be used.

The SSA requires the numerical results and the volume-time tracing (no flow-volume loops) from all three acceptable spirometry tests along with age, gender and height without shoes, along with the date of the tests. Arm span should be reported if the individual has kyphoscoliosis or other musculo-skeletal disorder that limits their ability to obtain an accurate height. Each of the volume-time graphs must be identified with the subject’s name and the date of the tests.

For DLCO the SSA requires at least two acceptable quality tests, which is defined as:

• Inspired volume at least 85% of FVC and that inspiration is less than 4 seconds.
• Breath-hold time of 8-12 seconds.
• Adequate washout volume (0.75 – 1.00 L when FVC ≥ 2.00 L and 0.50 L when FVC < 2.00 L)
• Adequate exhalation time (4 seconds for washout, 3 seconds for alveolar sample).
• The DLCO tests must be repeatable tests which is defined as within 3 mL CO (STPD)/min/mmHg of each other or within 10 percent of the highest value.

Somewhat surprisingly, DLCO results are to be reported without any correction for hemoglobin. This was not explained and given that anemia could be at least partly responsible for reduced DLCO results it’s unclear why this is the case.

The numerical DLCO results are reported along with

“…legible tracings of your VI, breath-hold maneuver, and volume of exhaled gas…”

As with spirometry, the subject’s age, gender and height without shoes needs to be reported. Arm span can be substituted for standing height if necessary. Each DLCO graph needs to identified with the subject’s name and date of testing.

ABGs must be performed at rest on room air without supplemental oxygen. The SSA does not have any requirements for how long somebody needs to be off their supplemental O2 but most labs ask their patients to be off their O2 for 15 to 30 minutes before an ABG and this should probably be adequate.

The SSA will accept an exercise ABG but specifies that it should be taken under steady-state conditions with no change in treadmill speed and elevation for at least 4 minutes. The treadmill speed and elevation is also supposed to be set for the equivalent of 5 mets (i.e. a VO2 of 17.5 ml/kg/min) which will likely limit which individuals can have this type of testing performed. If an individual is unable to exercise at this workload for 4 minutes then this needs to be documented along with the reason(s) they were unable to exercise long enough.

Only the PaO2 and PaCO2 (no pH), and the altitude or location (city and state) where the ABG sample was taken needs to be reported.

Pulse oximetry also needs to be performed while an individual is off any supplemental O2. The SSA requires that SpO2 measurement be stable, which they define as:

“…the range of SpO2 values (that is, lowest to highest) during any 15-second interval cannot exceed 2 percentage points.”

Depending on the apparent cause of the pulmonary disability the SSA may also require a graphical printout from a pulse Oximeter. Specifically:

“A graphical printout showing your SpO2 value and a concurrent, acceptable pulse wave. An acceptable pulse wave is one that shows the characteristic pulse wave; that is, sawtooth-shaped with a rapid systolic upstroke (nearly vertical) followed by a slower diastolic downstroke (angled downward).”

Pulse oximetry can be performed at rest, during a 6MWT or following a 6MWT and the SSA will use the lowest value. Results need to include the altitude or location (city and state).

The SSA webpage specifically discusses how asthma, cystic fibrosis, bronchiectasis, pulmonary hypertension, lung transplantation, respiratory failure, sleep related disorders are evaluated. Although COPD and Pulmonary Fibrosis are mentioned at various points they appear to be lumped together and evaluated as “chronic respiratory disorders”. The published rules are somewhat complicated (the SSA webpage should be consulted for specifics) and I suspect that there are a number of unwritten rules that could only be determined by looking at a number of case outcomes. For these reasons successful applications probably require at least some expert assistance.

How the pulmonary function results results are evaluated depends to some extent on what is causing the disability. For example the criteria for FVC and FEV1 are slightly different depending on whether the disability is due to chronic lung disease, asthma or cystic fibrosis. An adult (≥ 20 years) 5’ 9” (175 cm) male with COPD would need an FEV1 ≤ 1.75 L or an FVC ≤ 2.20 L. For the same person with asthma or cystic fibrosis an FEV1 would need to be ≤ 2.30 L (and FVC is not taken into consideration).

Pulmonary function results are in a sense the first stage of a disability evaluation, which is to prove the existence of an impairment. Simply because an individual meets one or more requirements in a disability evaluation does mean they will receive SSA disability status. As the SSA states:

“Once the existence of an impairment is established, SSA considers all evidence from all medical and nonmedical sources to assess the extent to which a claimant’s impairment(s) affects his or her ability to function in a work setting; or in the case of a child, the ability to function compared to that of children the same age who do not have impairments. Nonmedical sources include, but are not limited to: the claimant, educational personnel, public and private social welfare agency personnel, family members, caregivers, friends, neighbors, employers, and clergy. “

When we perform pulmonary function testing for a disability evaluation it is in the best interests of the patient that we meet all of the test quality and reporting guidelines. Whether we admit it or not, we have some wiggle room in routine clinical testing and by that I mean that after numerous tries we can (and will) accept the one good spirometry effort a patient was able to perform. When testing is for a disability evaluation however, if all the reported tests do not meet the quality, repeatablity and reporting requirements then this will significantly reduce the likelihood the patient will be able to receive a disability status, regardless of how badly they need it.

I’m still not sure why my lab gets so few patients for disability evaluations. This could be partly due to the referral patterns of local disability lawyers and physicians. It could also be due to the fact that most individuals with a pulmonary disability are older and already receiving Social Security benefits. But I also suspect that there are a lot of people who could qualify for SSA disability based on their pulmonary function results that don’t know they could.

The SSA has been criticized both for denying disability status for individuals that appear to have a clear need for it and for granting disability status to individuals who clearly don’t. In the first hospital I worked at my PFT lab usually got several disability evaluations every month and I have seen a full spectrum of applicants which has ranged from seriously ill individuals who were desperate to prove they were well enough to go back to work to obvious slackers who didn’t try to hide the fact that they were looking forward to sitting on a couch and watching TV for the rest of their lives. The problem we face is that the coaching we perform can significantly affect the results and this can leave us with the temptation to help – or hinder – an individual with their testing in order to get the results they “need”. But with disability testing in particular (and all testing in general) we shouldn’t perform any testing or report any results that we wouldn’t be willing to defend in a court of law. I say this not because I believe that has any particular probability of happening (it’s actually pretty unlikely) but more because it’s our responsibility to be a neutral party in this process and to do the best we can to get accurate and repeatable results.

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