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Trichogram
Dermatologists have always felt the need for an examination that
permits them to quantify the degree of alopecia of their patients
and to follow them over time to trace the evolution of the pathology
and, consequently, to change the therapy. Various techniques have
been used for this purpose, such as the hair pull test and the wash
test. The hair pull test, used by many dermatologists, is certainly
noninvasive, but it is a completely nonstandardized examination
and the results can be difficult for the clinician to appreciate.
The wash test, popular with a few European dermatologists, is not
a very specific technique and is probably only useful only with
regard to the telogen effluvium. However, another technique has
been developed that does give considerable, accurate data about
hair loss, the analysis method is called the "trichogram".
In essence, a trichogram involves taking 50 to 100 hairs from
different parts of the scalp. The procedure is straightforward.
The area from which the hair will be plucked is selected by the
dermatologist. The surrounding hair is combed out of the way and
held in place with hair clips. The dermatologist will then select
a bundle of hairs and put them in a clamp with rubber tipped ends.
The clamp is then used to pluck out the hair bundle in the direct
of the natural hair growth in that location. The hair is then stuck
on to a slide, usually with see through sticky tape or sometimes
embedded in a clear glue, and the clamp is released.
The hairs are then examined under a microscope or microfilm-reader
in order to determine which percentage of the hairs are in each
of the three phases of the hair growth cycle, anagen, catagen, or
telogen. Basically, anagen hair fibers usually have living cells
on the root end, and often a sheath of living cells (called the
the root sheath) around the lower hair fiber. Telogen hairs have
a club end to them and they do not have any living cells attached
to the root. Catagen hairs can be a bit more difficult to differentiate
but usually these hair fibers have a tapered end to the root. Anagen
and telogen plucked hairs may sometimes be difficult to distinguish
based on their microscopic appearance - at least for those inexperienced
in microscopic hair fiber examination. However, the citrulline-containing
proteins of the root sheath that is attached to plucked anagen hair
fibers develop a red color when stained with a dye called 4-dimethylaminocinnamaldehyde.
Plucked telogen hairs do not have any associated root sheath material
and so do not stain red. This histochemical stain helps improve
the accuracy of the telogen/anagen count. The hair fibers can also
be measured to find out how thick they are. This help determine
whether the hair fibers are normal terminal hairs, or intermediate
hairs (thin hair fibers) associated with chronic forms of hair loss
like pattern baldness and telogen effluvium.
In order to determine at what rate baldness will progress, the
proportion of anagen hairs (which are in their growing-phase) is
compared to the proportion of catagen and telogen hairs (which are
about to fall out). As a (very) rough guide, a 10% telogen frequency
is excellent, up to 25% is typical (the percentage of hairs normally
in the anagen phase is slightly higher with women and children than
with men), over 35% is a potential problem. By repeating the trichogram
over a time period, a hair loss condition can be followed. Equally,
if a treatment is being used, the effects of the treatment in terms
of changing the frequency of telogen hairs, can be measured.
The dermatologist may also take the hairs form specific sites depending
on the suspected hair loss problem. For example, if pattern baldness
is suspected, the dermatologist will take hair from two spots, one
on top of the head where the alopecia should be active, and one
from the back of the scalp where pattern baldness should not be
active. This enables the measurements made to the two hair samples
from different locations to be compared to each other. With pattern
baldness, the dermatologist would expect to see more telogen hair
on top of the scalp than at the back of the scalp. If the telogen
rate is about the same in both locations then the trichogram result
suggests that some other condition, like telogen effluvium, may
be involved.
So a trichogram can provide a fair amount of information in a quantitative
form about hair growth and hair loss and it can also show how effective
a hair loss treatment is. However, because the hair for examination
is plucked out, the trichogram is not popular with most patients.
Although the procedure is quite short and the pain associated with
plucking the hair does not last long, few people are willing to
submit to a trichogram. In addition, the trichogram is becoming
less popular with dermatologists. The examination of the hair takes
time and in the current climate where "patient through put"
in a clinic is all important, any technique that takes up significant
time is likely to be rejected. However some dermatologists, mostly
in Europe, will use the trichogram technique as a simple method
of quantifying hair loss.
If you plan to have a trichogram done, there are two things you
must do to make sure you get an accurate measurement. First, you
should not wash your hair in the 3 to 4 days preceding the test.
Washing helps massage out old telogen hair so washing shortly before
the trichogram is done can give an abnormally low telogen hair frequency.
The patient should also avoid permanent hair cosmetic treatments,
like perms, dyes, or straightening hair, up to 8 weeks before the
test is conducted. These permanent hair cosmetic treatments are
relatively damaging to hair fiber and can result in increased hair
breakage that can interfere with the evaluation.
Unit
area trichogram
The basic trichogram provides information about the number of
anagen hairs and telogen hairs from different parts of the scalp.
While this information is accurate and quantitative, it only reveals
part of the story. It tell us how many hair fibers are growing,
but it takes not account of those hair follicles that may not contain
any hair fibers at all. It does not tell us about the density of
the hair on the scalp and hair density (scalp coverage) is the primary
concern for any individual experiencing hair loss. In response to
this deficiency, the standard trichogram can be taken several steps
further and developed into a variation of the trichogram called
the "unit area trichogram".
In the unit area trichogram procedure the plucked hairs are taken
from an area of skin that is measured. So for example, a circle
a centimeter in diameter my be marked on the skin and then all the
hairs in that circle will be plucked out and examined. In this way
the number of anagen, catagen, and telogen hairs counted can be
used to define the density of these hair types per unit area of
skin. This density measurement gives an idea of how thick or thin
the hair coverage over the scalp skin is. The dermatologist can
say you have x anagen hairs and x catagen/telogen hairs per square
centimeter of scalp skin. Knowing what the normal hair fiber density
is for the average person from published studies (ranges from 200
to 300 hair fibers per square centimeter depending on ethnicity),
the patient's evaluation can be presented in terms of how close
his/her hair density is to the normal, expected value. If the measurement
is repeated over time the dermatologist can say whether the hair
coverage is getting thicker or thinner. This method quantifies the
cosmetic appearance of scalp hair growth. It can be used to see
how well a hair loss treatment is performing and how much new hair
the treatment has induced to grow.
As well as looking at the frequency and density of the hair fiber
types, the diameters of the hair fibers may be measured under the
microscope. Normal terminal hairs should have a diameter of 80 micrometers
of above for most people. Between 40 micrometers and 80 micrometers
diameter the hair fibers are usually defined as "intermediate
hairs". These hairs are not healthy, but they are thick enough
to contribute to the overall coverage of the scalp skin. Below 40
micrometers diameter the hair fibers are certainly not healthy and
they do not help much to cover the skin. This fine hairs are usually
well on their way to becoming vellus hairs if they have not already
reached that state. So by taking the additional step of measuring
the plucked hairs' diameters, the dermatologist can determine the
density of healthy hairs, or the density of those hairs that can
contribute to hair coverage. Such detailed information may not mean
so much to a patient, but in research studies, especially those
looking at response to treatments, this kind of data is very helpful.
Trichogram
and unit area trichogram references
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hair growth. Australas J Dermatol. 2003 Feb;44(1):10-8.
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and clinical relevance of a novel scalp coverage scoring method.
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Dermatol. 2002 Jul;27(5):358-65.
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the skin, vol. 1. Ann Arbor, CRP Press, 1995: 543-8.
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for measuring the various constituents of the human hair follicle.
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area trichogram in the assessment of androgen-dependent alopecia.
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plucked anagen hairs. J Am Acad Dermatol. 1979 Aug;1(2):121-2.
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trichogram of the adult. J Invest Dermatol. 1965 Apr;44:233-6.
- Pecoraro V, Astore I, Barman J, Ignacioaraujo
C. The normal trichogram in the child before the age of puberty.
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