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15.0
Treatment Protocols
15.1
MED Testing
The more accurate but more complicated method of determining a patient's initial dose is through MED
testing. Because this is a cumbersome process, many doctors do not wish to determine a patient's initial
dose in this manner. However, before we discuss the procedure in greater detail, let us first define the
terms.
MED stands for Minimum Erythemal Dose and is defined as the minimal dose of UVB that will cause
marked erythema on a patient's skin. As an example, a skin type IV will have an MED somewhere within
the range of 200-600 milliJoules of narrow band UVB. See Protocols for all skin types and ranges.
MED testing results in a more accurate starting point. Because of the subjective nature of a patient's
response to the skin-typing quiz, the empirical method is more subject to error. In many cases, testing will
show that a patient may be more tolerant to ultraviolet than would have been suggested by simple skin
typing.
It is important to start phototherapy patients at as high a dose as possible. Underdosing a patient causes
excessive tanning that means that the patient must undergo more and more aggressive treatment just to
overcome the natural UV screening effect of tanned skin. This results in an excessively high cumulative
dose to clear the patient's disease.
When setting up a UVA-1 patient, the key element in determining exactly how much UVA-1 radiation the
patient will receive is the MED. The first UVA-1 treatment is always a percentage of the MED that has
been entered. Thereafter, each succeeding treatment is some percentage of the preceding dose. Each and
every dose is mathematically related to the MED value, whether this value was determined by MED testing
or by skin typing.
The following section provides instructions on exactly how MED testing is carried out in the doctor's office.
15.2
MED Testing Procedure
The
first stage in performing MED testing is to determine the patient’s skin type. The patient’s skin type
is then used to determine the dosages that will be used to perform MED testing. Many physicians use a
simple table of questions to determine a patient's tolerance to light. The table is reproduced below:
Skin Type
History
Skin Type I
Always burns, never tans
Skin Type II
Always burns, sometimes tans
Skin Type III
Sometimes burns, always tans
Skin Type IV
Always tans, never burns
Skin Type V
Brown skinned (Chinese, Mexican American)
Skin Type VI
Black
Once you have determined the patient’s skin type you can proceed to the testing stage.
