The Collins test

The Collins Test is a vital staining test of epithelium, performed by staining the vulvar skin with methylene blue. Subsequently, after washing off the excess dye with a physiological solution, the suspicious lesions retain the applied blue color and become more visible for taking biopsy sampling. It is often used as a complement to colposcopy due to its enhanced visibility of suspicious changes.

The test is based on ability of the epidermis to retain the applied blue color in cases of parakeratosis and/or dyskeratosis.