Diagnostic Procedures
When tinea capitis is suspected:
Fungal culture by scraping the affected areas with a blunt scalpel, a sterile brush or moistened gauze to gather affected hairs;
Woods lamp examination: as screening to detect flourescing species, such as Microsporum;
A potassium hydroxide preparation (to reveal hyphae): a scalp scraping or plucked hairs from the affected area.
When alopecia areata is suspected:
Thyroid function
When telogen effluvium is suspected:
Hair pull test (already described);
If there is no obvious trigger of telogen effluvium tests include:
Sedimentation rate, complete blood count;
Serum ferritin;
Antinuclear antibody;
Thyroid function test;
Serology for syphilis.
When scarring alopecias are suspected:
4-mm punch scalp biopsy
When hereditary hair shaft disorders are suspected:
Serum biochemistry: for metabolic disorders;
To analyze hair structure:
Hair mount examination by light and polarizing microscopy;
Scanning or transmission electron microscopy, or both.
To analyze biochemical composition of affected hair.
Amino acid analysis by chromatography, spectroscopy (cysteine and sulfur content);
Keratin analysis.
Newer techniques:[7–14]
Videodermoscopy: the magnified images of hair follicle are useful for the differential diagnosis between cicatricial and noncicatricial alopecia and between alopecia areata and trichotillomania;
Trichoscan: it is an automated software program for the accurate analysis of hair growth and useful in monitoring the response to treatment;
Contrast-enhanced phototrichogram: a technique used to analyze hair growth activity using photographic records and a scalp immersion proxigraphy method.
Frequent causes of alopecia encountered in general practice are discussed below.
Expert Rev Dermatol. 2011;6(6):581-590. © 2011 Expert Reviews Ltd.
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