ARTICLE
Over the last decade, innovations in biotechnology have progressively
invaded medicine. This has facilitated the investigation of the human
physiopathology by simplifying the physician's work and by standardizing
clinical data, rendering them more easily interchangeable among various
groups of study. Accordingly, an attempt has been made to shed some of
modern technology's light onto the field of trichology, one still hampered
by areas of darkness.
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 [1, 2], such as the
wash test, pull test and trichogram. Particular qualities and defects
characterise each of these techniques. Thus the choice of which examination
to perform has always been linked to the individual preferences of the
dermatologist.
The wash test is not a very specific technique and is useful only with
regard to the telogen effluvium. However, it allows a quick identification
of those neurotic patients whose condition aggravates the real amount
of the defluvium. The pull test is a totally non-standardised examination
the results of which are difficult for the clinician to appreciate [3].
The trichogram [4] is a semi-invasive technique of great help to the clinician
in the evaluation of alopecia, but poorly tolerated by the patient.
Today, modern biotechnology offers us the possibility of devising a
technique that will guarantee greater degrees of simplicity, reproducibility
and sensitivity and that might eventually become a feasible examination
in a larger range of cases.
The phototrichogram, introduced by Saitoh in 1970 [5], is a non-invasive
technique that allows the in vivo study of the physiology of the
hair cycle and the quantification of the amount of defluvium.
Today, the technique has been improved thanks to the advent of computer-assisted
image analysis. Substantially, however, Saitoh's idea and method are still
valid.
The purpose of our work is to contribute to the definitive standardisation
of the technique in view of the new possibilities offered by information
technology and biotechnology, in general.
Materials and methods
Between January 1998 and April 2000, we enrolled 28 healthy volunteers
(20 women and 8 men) between the ages of 18 and 30 (average age was 23.32
± 3.48 years). The subjects were fully aware of the nature of the
study and all gave their informed consent. They followed a standardised
procedure that imposed shampooing the hair once the week prior to sampling.
They were also not allowed to use cosmetic hair products.
The examination was performed by a computerised optical probe videomicroscope
(Videocap 200, DS MediGroup) equipped with a rigid frame that enabled
photos always to be taken from a fixed distance from the scalp (the section
of the frame in contact with the scalp contained a window equipped with
a glass slide to flatten the hair to the scalp surface), and lenses with
x 20 or x 50 factors of magnification (the actual sizes of the scalp sites
thus photographed were respectively 196.4 mm2 and 25 mm2).
A 1 cm2 area of the scalp on the vertex was delineated and
the hair within this area was shaved to 0.2 mm from the scalp. This area
was marked by a micro-tattoo.
Immersion oil was put between glass and scalp to increase the optical
qualities of the images (Scalp Immersion Proxigraphy [6]).
A photo of the area with x 20 enlargement and two photos with x 50 enlargements
of two adjacent sites in the same area were taken immediately after shaving
the hair (t0) and after 48 hrs (t48).
The clipped hair shafts were placed on a sheet of white paper and observed
with a x 200 lens in immersion to evaluate the diameter.
Collected images were digitised and stored in the computer's memory.
The software for controlling the instrument and for the processing of
the images (growth rate and hair diameter evaluation [7]) was that provided
by the manufacturer. At the first time interval (t0), our evaluation considered:
- Hair density (identification of each hair emerging from the follicular
ostium).
- Hair diameter.
- Percentage of thin hairs (< 40 micron in diameter).
At the second time interval (t48) (the optical fiber probe being positioned
exactly as in t0 with the help of the tattoo), each hair was identified
and its growth evaluated; so it was possible to obtain the following data:
- Percentage of hairs in the anagen phase (they appear longer in
the second picture than in the first one).
- Percentage of hairs in the telogen phase (In the second picture
they have not grown with respect to the first picture).
- Anagen/telogen ratio.
- Growth rate (mm/day). [(t0 hairs length) - (t48 hairs length)]/2.
Two independent observers completed the evaluation in a blind manner
and the results were expressed as the average ± SD.
Differences between values obtained with x 20 and x 50 enlargements
were compared statistically by Student's t-test. A
P-value < 0.05 was considered as statistically significant.
Results
The results obtained by x 50 enlargement (Fig.
1a, b) can be summarised as follow: the total hair density was
260 ± 30/cm2 in men and 300 ± 20/cm2 in
women; the telogen percentage was higher in men (16.5 ± 1.5% vs 11
± 1% of women); thin hairs (< 0.040 mm) were 9.4 ± 1.8% in
men and 9 ± 2% in women (they could represent both the early stages
of anagen phase or vellus hairs of androgenetic alopecia); the growth
rate (Fig. 2) was 0.35
± 0.03 mm/day in men and 0.38 ± 0.03 mm/day in women. The hair
diameter, obtained using a x 200 enlargement (Fig.
3) with immersion oil, was 0.084 ± 0.013 mm both in men and
in women.
In Table I, we report
the values obtained from the 28 volunteers as revealed by the x 50 enlargement.
In Table II, we report
the comparison between average values respectively obtained with x 20
and x 50 enlargements in the 28 healthy volunteers.
Discussion
In the evaluation of the 28 volunteers, we observed, in agreement with
the literature [8], that the enlargement factor employed significantly
influenced the measurement of total hair density. In particular, the x
20 enlargement significantly underestimates hair density. Consequently,
the x 50 enlargement is suitable, although it presents the problem of
reducing the scalp area under investigation. The sample size of hairs
thus evaluated is too small for statistical purposes, so that it is preferable
to use the x 50 enlargement to investigate two sites for the same patient.
Our findings show that measurements with x 20 enlargement underestimated
the total hair density by approximately 30% compared to the average value
(in the two photos) obtained with the x 50 enlargement (Table
II) (Fig. 1a, b). With
x 20 enlargement, it is particularly difficult to see thin hair (<
0.040 mm diameter) and therefore the difference between the values obtained
with x 20 and x 50 enlargements could increase when investigating patients
suffering from androgenetic alopecia, who have greater numbers of vellus
hairs. Furthermore, we noticed a considerable difference between x 20
and x 50 generated values for growth rates (Table
II, Fig. 2).
The digital videomicroscope with the x 200 lens allows for a more exact
evaluation of the hair diameter. There was only a slight difference between
values obtained with the x50 enlargement and with the x 200 enlargement
(Table II, Fig. 3). During
this evaluation, when hairy shafts are put on the white paper, as described
before, it is also possible to observe the characteristics of the trunk
(Moniletrix, Trichorrexis nodosa, Pili torti, breaks of the shaft) as
with a normal microscope.
The phototrichogram is a non-invasive and painless exam, easy for the
operator to execute and well tolerated by the patient [9]. Certainly,
patients accept it more easily than the classic trichogram [10] which,
instead, requires the tearing of a tuft of hairs. Even if well executed,
the latter operation is obviously painful and, if not properly done, it
can modify the characteristics of the bulbs and thus produce errors in
the counting of the anagen and telogen hairs. On the contrary, in the
phototrichogram, this counting is carried out directly on the scalp (in
vivo), which permits a more accurate distinction between anagen and
telogen hairs and avoids the technical problem. The phototrichogram also
allows evaluation of total hair density, an important index of the degree
of defluvium. Furthermore, the digital videomicroscope with x 50 and x
200 enlargements permits the estimation of morphological parameters (microvascular
status of the scalp, presence of empty follicles, peripilar atrophy, scales
and seborrhea) which supplies further information for a complete study
of alopecia.
The most important advantage of the phototrichogram is that it is possible
to repeat the examination on the same area of the scalp monthly, so that
each hair can be identified and followed across the various phases of
the hair cycle. In this way, a virtual map of the anagen and telogen hairs
on the scalp can be drawn. This allows the study of the hair cycle and
its changes linked to therapies and aging [11]. It is impossible to perform
these studies with the classic trichogram.
The videomicroscope facilitates the work of
the operator not only in the technical execution of the examination (it
reduces the difficulties of handling and focusing) but also in the evaluation
of the results, which can be carried out directly on the computer monitor
or by printing the images on photographic paper. Furthermore it is easily
executable by inexpert operators. Thanks to the digital image, in this
phase the operator can alter the colour contrasts, magnify some details
or use filters that could enhance a clear perception of the thin or few
pigmented hairs that are hard to observe in ordinary photos.
The phototrichogram encounters great difficulty in estimating total
hair density in subjects with gray or fair-colored hair [12]. In fact,
fair-colored hair is not sufficiently pigmented to be well distinguished
from the scalp and therefore it is visible only by careful observation,
which may cause some errors of evaluation. But experience and skill can
help to overcome this handicap. Furthermore, unlike with the trichogram
[4], it is impossible to distinguish the dystrophic or dysplastic anagen
hair from the normal anagen hair and the catagen from the telogen with
the phototrichogram. However, this condition does not alter the scientific
value of the examination. Another limitation of the phototrichogram is
the necessity of the tattoo, although it is small in size and aesthetically
unnoticeable. But the tattoo is really only required to follow the hair
cycle monthly and can be avoided for the execution of a single examination.
Finally, the phototrichogram performed with the digital videomicroscope
permits the assessment of functional (in vivo) and morphological
parameters and gives a notable advantage in the management of patient's
alopecia. The phototrichogram could be a valid aid for clinical diagnosis,
but above all, it is important in the assessment of the degree of defluvium
and in the evaluation of the development of alopecia and the effectiveness
of therapies.
Thanks to its integration with digital imaging, the phototrichogram
has undoubtedly become an examination of primary importance in trichology
because of its simplicity and sensitivity even if it cannot as yet be
considered the ideal technique to replace all the others. In fact, the
wash test, pull test and trichogram still have some advantages that make
them preferable in special circumstances. Thus, today it is very important
to know the characteristics of each technique in order to be able to choose
the most suitable one according to the circumstances.
REFERENCES
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