# Bedside Clinical Tests in Dermatology

> Bedside tests in dermatology for NEET-PG, covering diascopy, grattage, dimple test, dermographism, hair pull test and sensory testing with expected findings.

- Canonical URL: https://prepelephant.com/topics/neet-pg/dermatology/bedside-clinical-tests-in-dermatology
- Exam / course: NEET-PG · Subject: Dermatology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Rook's Textbook of Dermatology; Fitzpatrick's Dermatology; Andrews' Diseases of the Skin
- How to cite: "Bedside Clinical Tests in Dermatology", PrepElephant, https://prepelephant.com/topics/neet-pg/dermatology/bedside-clinical-tests-in-dermatology

## Direct answer

Bedside clinical tests in dermatology are simple manoeuvres, done with a glass slide, a fingertip, a blunt instrument or a hair tuft, that reveal diagnostic features without a laboratory. Diascopy shows whether a colour is vascular or granulomatous, and the dimple test identifies a dermatofibroma. Sensory testing with light touch, pinprick and temperature maps the anaesthesia of leprosy and other neuropathies.

## What you must remember

- **Diascopy:** pressing a glass slide on a lesion; vascular erythema blanches, whereas granulomatous colour persists.
- **Apple-jelly nodules:** brownish-yellow colour on diascopy, typical of lupus vulgaris and sarcoidosis.
- **Grattage test:** scraping the scale of a lesion to elicit the Auspitz sign, characteristic of psoriasis.
- **Dimple test:** squeezing the skin beside a dermatofibroma produces inward dimpling, because the lesion is anchored in the dermis.
- **Dermographism:** firm stroking produces a linear wheal, and symptomatic dermographism is linked to urticaria.
- **Hair pull test:** gentle traction on a tuft of hair; more than about 10 per cent of the tuft (over six hairs) coming away indicates active shedding.
- **Sensory testing:** light touch, pinprick and temperature are tested separately over hypopigmented patches, and loss suggests leprosy.
- **Darier sign:** a wheal on stroking a lesion of urticaria pigmentosa, from mast cell degranulation.

## A bedside sequence for a skin examination

Bedside tests are quick and cost nothing, so they belong early in the examination and before a biopsy is planned. Each test narrows the differential, and the findings are recorded in the case note in the same order they were obtained.

1. **Press with a glass slide:** perform diascopy on any red or brown lesion, and note whether the colour blanches or persists.
2. **Scrape any scale:** use a glass slide or blunt edge to perform the grattage test on scaly plaques and look for pinpoint bleeding.
3. **Squeeze a firm nodule:** test for the dimple sign by pinching the skin beside a suspected dermatofibroma.
4. **Pull a tuft of hair:** apply gentle traction to a small bunch of hairs, then count the loose hairs and their roots.
5. **Map sensation:** test light touch, pinprick and temperature over any hypopigmented or anaesthetic patch, and compare with normal skin.

The findings guide the next investigation, but they do not replace a biopsy or a laboratory test when the diagnosis is unclear. Record each test result in the case note, including negative findings, since a negative test also narrows the differential.

## Where bedside tests catch candidates

Bedside tests are easy to recall, but examiners set traps around what each finding means.

- **Trap:** calling persistent apple-jelly nodules simple erythema — **Correct:** vascular erythema blanches on diascopy, whereas apple-jelly nodules persist, showing a granulomatous colour.
- **Trap:** treating a positive hair pull test as diagnostic of alopecia areata — **Correct:** a positive result shows active shedding, which occurs in telogen effluvium and alopecia areata alike, so it does not identify the cause.
- **Trap:** testing only pinprick in a leprosy patch — **Correct:** test light touch, pinprick and temperature separately, since different sensory modalities can be affected unequally.
- **Trap:** confusing the Darier sign with Darier disease — **Correct:** the Darier sign is a wheal on stroking urticaria pigmentosa, whereas Darier disease is a genetic keratinisation disorder.

## Frequently asked questions

### What does diascopy show in lupus vulgaris?

Diascopy in lupus vulgaris shows apple-jelly nodules, which are brownish-yellow and persist under the glass slide. This colour reflects granulomatous tissue, whereas vascular erythema would blanch under the same pressure.

### What does a positive dimple sign indicate?

A positive dimple sign, in which squeezing the skin produces inward dimpling, indicates a dermatofibroma. The dimpling occurs because the lesion is anchored to the overlying dermis, and it helps separate the lesion from cysts and lipomas.

### What does a positive hair pull test suggest?

A positive hair pull test shows active hair shedding, with a clearly increased number of loose telogen hairs. Telogen effluvium and alopecia areata can both produce it, so the test must be interpreted with the history and trichoscopy.

### Which bedside sensory test helps identify leprosy?

Sensory testing with light touch, pinprick and temperature over a hypopigmented patch helps identify leprosy, because loss of sensation in the patch suggests nerve involvement. Each modality should be tested separately, since they can be affected unequally.

### What does dermographism indicate in urticaria?

Dermographism is a linear wheal that appears after firm stroking of the skin, and symptomatic dermographism is linked to urticaria. It is a clinical finding that helps classify urticaria and guides the investigation of its triggers.