National Health and Nutrition Examination Survey

One in three Americans has a skin condition serious enough to require medical attention. However, there are major gaps in knowledge about the frequency, impact, etiology and prevention of most skin diseases.
Psoriasis affects the health related quality of life in ways similar to other major medical conditions. Studies of disability caused by psoriasis, such as arthritis, indicate that level of disability for those with the condition are greater than that of healthy controls. There is also an association between psoriasis and stress, as well as depression.

Hand dermatitis is the most common occupational skin disease, as well as a common cause of occupational disability. Acute eczematous dermatitis is one of the few skin diseases that, according to Americans with Disabilities Act of 1990, may still be used as a reason for exclusion fromemployment. The estimated cost associated with this condition is greater than $300 million dollars a year.

The Fitzpatrick skin type is a method of classifying individuals based on their response to sun exposure in terms of tanning and burning (photosensitivity) (Fitzpatrick, 1988).

Fitzpatrick Classification of Skin Type
I - Always burns, never tans (pale white skin)
II - Always burns easily, tans minimally (white skin)
III - Burns moderately, tans uniformly (light brown skin)
IV - Burns minimally, always tans well (moderate brown skin)
V - Rarely burns, tans profusely (dark brown skin)
VI - Never burns, (deeply pigmented dark brown to black skin)

Individuals’ susceptibility to different skin conditions and diseases is known to vary by skin type. Currently, the distribution of skin type across the U.S. population is unknown. Knowing more about the U.S distribution of skin type will be helpful in developing more accurate measures of risk factors for various skin conditions and diseases. It may also be important to the development of better national health education campaigns regarding sun protective behavior.

Sample persons aged 20-59 years who do not meet any of the exclusion criteria.

Exclusion Criteria:

A person using a wheelchair did not receive the photos of the back or back of the legs. He/she would be eligible for the other photos. There are no safety exclusions for this component.

Protocol:

The exam consists of four digital images taken by a health technician using a Kodak DCS760 digital camera with a 50mm lens. The poses were as follows:

“BACK with ELBOWS”

• Back of gown is opened and clipped to expose subject’s back.
• Sticky rule is placed on subject’s back.
• Arms are rotated out to square up the elbows.
• Top of shot at subject’s neck (no head).
• Camera focus indicator is on subject’s spine.

“INNER ARM”

• Subject’s gown is closed and they are instructed to turn around and face the camera.
• Subject extends the left arm to the left side, with palm up.
• Top of shot is Subject’s neck (no head).

“FRONT OF LEGS with HANDS”

• Subject is instructed to face the camera.
• Subject places hands on lower abdomen, with fingers extended, for tops of hands.
• Bottom of shot is just below subject’s ankles.
• Camera focus indicator is on back of subject’s Gown.

“BACK OF LEGS with PALMS”

• Subject’s back is to the camera.
• Subject places hands behind back on lower hips, with palms flattened and fingers spread.
• Bottom of shot is just below subject’s ankles.
• Camera focus indicator is on back of subject’s gown

In addition, the readers made an assessment of image quality. They evaluated the image on the following criteria – focus, shadows, positioning of subject, and “other”. The other category allowed readers to identify difficulties with the image for reasons other than those listed above.

All data from each of the sections of the Dermatology Examination Component were directly entered by MEC technicians into ISIS, a computerized database information system. Health technicians in the Mobile Examination Centers were trained in the protocol by expert consultants in digital photography. In addition, Dermatology consultants from the NIH/National Institute of Arthritis and Musculoskeletal and Skin Disease (NIAMS) and contractor staff provided performance monitoring of each Health technician on a regular, periodic basis. Additionally, NCHS staff visited the MECs approximately twice per year per examination team to observe the Dermatology examinations and verify that standard testing procedures were being strictly followed by technicians. All MEC Dermatology technicians also received annual retraining and updates by the NIAMS consultants. Finally, exclusion rates and outcome statistics were continually monitored by NCHS according to technician and MEC, and retraining was conducted as necessary to maintain test quality.

For details on the QA/QC process for this component, please refer to the Interviewer Procedure Manuals on the NHANES website.

All data were captured in ISIS, a computerizeddatabase. NCHS performed data reviews on an ongoing basis using a computerized data editing program to check for logical inconsistencies in the data and technician errors, as well as to check other issues affecting data quality. Back-end edits of the data were performed as necessary where errors were detected. The 2003–2004 Dermatology Examination data were reviewed for errors and logical consistency and verified against the primary examination data database prior to public data release.

Because the NHANES 2003–2004 Dermatology examination was administered in the MEC, the full sample MEC examination sample weight should be used for data analysis. For information on the use of sample weights in NHANES data analysis, refer to the NHANES 1999–2000 and 2003-2004 Addendum to the NHANES III Analytic Guidelines. NHANES 2003–2004 dermatology data was collected for a full sample of U.S. adults ages 20-59.

The dermatology digital images were read by two separate dermatologists. When the finding of the two readers disagreed, the image reading software program required a third consensus reading. For the consensus readings, both dermatologists reviewed the image for findings at the same time and came to a unified decision. The variable names for data based on Reader 1 contains the number 1 (DEX1, DEA1, etc.). Findings from Reader 2 contain the number 2 in the variable name (DEX2, DEA2, etc.) Variable names for the consensus reading assessments contain the number 6 (DEX6, DEA6,etc.). The algorithm used for consensus readings is given below:

Consensus Rules

Rule 1:

Sample person (SP) images go to consensus if the two readings for Hand Dermatitis are not on the list of acceptable combinations:

Rule 2:

Sample person (SP) images go to if the two readings for Psoriasis are not on the list of acceptable combinations (same as above).

Rule 3:

Sample person (SP) images go to consensus for values given for Fitzpatrick Skin Type in accordance with the following matrix. Value range is 1-6 for each reader. (Readings for reader 1 on rows and for reader 2 in columns.) Any outcome that resulted in “reject” went to consensus.

Rule 4:

If any critical value is missing for either reader the sample person’s image is sent for consensus reading.

Critical values include:

• Fitzpatrick Skin Type
• Hand Dermatitis or Psoriasis Present/Absent
• Confidence (if Hand Dermatitis or Psoriasis is present only)
• Location (if Hand Dermatitis or Psoriasis is present only)

In addition, a consensus reading was required for any condition requiring follow-up.

Please refer to the Analytic Guidelines on the NHANES website for further details on the use of sample weights and other analytic issues.