When we decide whether you have a "marked" or an "extreme" limitation, we will consider your functional limitations resulting from all of your impairments, including their interactive and cumulative effects. We will consider all the relevant information in your case record that helps us determine your functioning, including your signs, symptoms, and laboratory findings, the descriptions we have about your functioning from your parents, teachers, and other people who know you, and the relevant factors explained in DI 25210.001 ff., DI 25215.001 ff., and DI 24501.020.

The medical evidence may include formal testing that provides information about your development or functioning in terms of percentiles, percentages of delay, or age or grade equivalents. Standard scores (e.g., percentiles) can be converted to standard deviations. When you have such scores, we will consider them together with the information we have about your functioning to determine whether you have a "marked" or "extreme" limitation in a domain.

We will find that you have a "marked" limitation in a domain when your impairment(s) interferes seriously with your ability to independently initiate, sustain, or complete activities. Your day-to-day functioning may be seriously limited when your impairment(s) limits only one activity or when the interactive and cumulative effects of your impairment(s) limit several activities. "Marked" limitation also means a limitation that is "more than moderate" but "less than extreme." It is the equivalent of the functioning we would expect to find on standardized testing with scores that are at least two, but less than three, standard deviations below the mean.

If you have not attained age 3, we will generally find that you have a "marked" limitation if you are functioning at a level that is more than one-half but not more than two-thirds of your chronological age when there are no standard scores from standardized tests in your case record.

If you are a child of any age (birth to the attainment of age 18), we will find that you have a "marked" limitation when you have a valid score that is two standard deviations or more below the mean, but less than three standard deviations, on a comprehensive standardized test designed to measure ability or functioning in that domain, and your day-to-day functioning in domain-related activities is consistent with that score. (See DI 25225.020D.)

For the sixth domain of functioning, "Health and physical well-being," we may also consider you to have a "marked" limitation if you are frequently ill because of your impairment(s) or have frequent exacerbations of your impairment(s) that result in significant, documented symptoms or signs. For purposes of this domain, "frequent" means that you have episodes of illness or exacerbations that occur on an average of 3 times a year, or once every 4 months, each lasting 2 weeks or more. We may also find that you have a "marked" limitation if you have episodes that occur more often than 3 times in a year or once every 4 months but do not last for 2 weeks, or occur less often than an average of 3 times a year or once every 4 months but last longer than 2 weeks, if the overall effect (based on the length of the episode(s) or its frequency) is equivalent in severity.

We will find that you have an "extreme" limitation in a domain when your impairment(s) interferes very seriously with your ability to independently initiate, sustain, or complete activities. Your day-to-day functioning may be very seriously limited when your impairment(s) limits only one activity or when the interactive and cumulative effects of your impairment(s) limit several activities. "Extreme" limitation also means a limitation that is "more than marked." "Extreme" limitation is the rating we give to the worst limitations. However, "extreme limitation" does not necessarily mean a total lack or loss of ability to function. It is the equivalent of the functioning we would expect to find on standardized testing with scores that are at least three standard deviations below the mean.

If you have not attained age 3, we will generally find that you have an "extreme" limitation if you are functioning at a level that is one-half of your chronological age or less when there are no standard scores from standardized tests in your case record.

If you are a child of any age (birth to the attainment of age 18), we will find that you have an "extreme" limitation when you have a valid score that is three standard deviations or more below the mean on a comprehensive standardized test designed to measure ability or functioning in that domain, and your day-to-day functioning in domain-related activities is consistent with that score. (See DI 25225.020D.)

For the sixth domain of functioning, "Health and physical well-being," we may also consider you to have an "extreme" limitation if you are frequently ill because of your impairment(s) or have frequent exacerbations of your impairment(s) that result in significant, documented symptoms or signs substantially in excess of the requirements for showing a "marked" limitation in DI 25225.020B.4. However, if you have episodes of illness or exacerbations of your impairment(s) that we would rate as "extreme" under this definition, your impairment(s) should meet or medically equal the requirements of a listing in most cases. See DI 25220.010.

As indicated in DI 25210.001B.2., we will not rely on any test score alone. No single piece of information taken in isolation can establish whether you have a "marked" or an "extreme" limitation in a domain.

We will consider your test scores together with the other information we have about your functioning, including reports of classroom performance and the observations of school personnel and others.

1. a. 

   We may find that you have a "marked" or "extreme" limitation when you have a test score that is slightly higher than the level provided in DI 25225.020B or DI 25225.020C, if other information in your case record shows that your functioning in day-to-day activities is seriously or very seriously limited because of your impairment(s). For example, you may have IQ scores above the level in DI 25225.020B, but other evidence shows that your impairment(s) causes you to function in school, home, and the community far below your expected level of functioning based on this score.

2. b. 

   On the other hand, we may find that you do not have a "marked" or "extreme" limitation, even if your test scores are at the level provided in DI 25225.020B or DI 25225.020C, if other information in your case record shows that your functioning in day-to-day activities is not seriously or very seriously limited by your impairment(s). For example, you may have a valid IQ score below the level in DI 25225.020B, but other evidence shows that you have learned to drive a car, shop independently, and read books near your expected grade level.

If there is a material inconsistency between your test scores and other information in your case record, we will try to resolve it. The interpretation of the test is primarily the responsibility of the psychologist or other professional who administered the test. But it is also our responsibility to ensure that the evidence in your case is complete and consistent or that any material inconsistencies have been resolved. Therefore, we will use the following guidelines when we resolve concerns about your test scores:

1. a. 

   We may be able to resolve the inconsistency with the information we have. We may need to obtain additional information; e.g., by recontact with your medical source(s), by purchase of a consultative examination to provide further medical information, by recontact with a medical source who provided a consultative examination, or by questioning individuals familiar with your day-to-day functioning.

2. b. 

   Generally, we will not rely on a test score as a measurement of your functioning within a domain when the information we have about your functioning is the kind of information typically used by medical professionals to determine that the test results are not the best measure of your day-to-day functioning. When we do not rely on test scores, we will explain our reasons for doing so in your case record or in our decision.