Hair perforation test is positive in infection with –
**Core Concept**
The hair perforation test is a clinical examination technique used to assess the integrity of the hair and its surrounding structures. It involves gently pushing a hairpin or a needle through the hair shaft to check for any signs of infection or inflammation.
**Why the Correct Answer is Right**
A positive hair perforation test indicates the presence of an infectious process, particularly fungal infection, that leads to the destruction of the hair shaft and the surrounding tissues. The fungus, such as Trichophyton rubrum, invades the hair follicle and causes inflammation, leading to the weakening of the hair shaft. As a result, the hair can be easily perforated with a hairpin or needle.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the hair perforation test is not typically used to diagnose bacterial infections, which usually cause different types of skin and hair lesions.
**Option B:** This option is incorrect because the hair perforation test is not a reliable method for diagnosing viral infections, which often cause different clinical manifestations.
**Option C:** This option is incorrect because the hair perforation test is not a diagnostic tool for diagnosing parasitic infections, which usually cause different types of skin and hair lesions.
**Clinical Pearl / High-Yield Fact**
A positive hair perforation test is often associated with fungal infections, such as tinea capitis, which is a common cause of hair loss in children.
**Correct Answer:** C.