Methods of determining hair loss
The following methods are often used to determine hair loss:
- Scalp biopsy
In a scalp biopsy, a small amount of the scalp is removed and examined.
The trichogram exam is a microscopic examination of the hair root after being plucked out. It shows the relationship between hair in the growth phase (anagen phase), in the resting phase (telogen phase) and in the transition phase (catagen phase). This determines how advanced the hair growth is at the time of the exam.
Up to 100 hairs are required for the trichogram. The areas of hair removal are determined by the doctor depending on the type of hair loss. Normally, one to two points of hair removal on the front and back of the head are necessary to provide an informative result. The growth phases of the individual hairs can be determined by looking at the shape and colour of the plucked out hair roots under the microscope.
A modified version of the trichogram is the trichoscan. The trichoscan determines the hair density and the relation between growing and non-growing hairs on the scalp using imagery. The trichoscan also serves to obtain data on the hair density and the activity status of the hair follicle. As this is an imagery method used directly on the patient, the trichoscan provides all significant parameters of hair growth in a single step, unlike the trichogram.
In the trichoscan exam, a small area of the scalp is initially shaved. After 3 days, the shaved area is dyed whereby both the hair that has grown back and the hair that has not grown is made visible. Then, an image enlarged by a factor of around 20 is taken. Since anagen hair normally grows around 0.3 mm per day and telogen hair cannot grow any more, the number of hairs per cm2 and the ratio of anagen to telogen hairs is calculated.
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