Waddell nonorganic signs
Physical examination signs that are often used to assess for nonorganic or psychological components of back pain. These signs include superficial or nonanatomic tenderness, pain on axial loading or simulated rotation, nonreproducibility of pain when patient is distracted, regional weakness or sensory change, and overreaction. Waddell signs were designed to assess current pain rather than to predict future disability and have not been studied for that purpose.

Washout period
In a crossover or N-of-1 trial, the period required for the treatment to cease to act once it has been discontinued.

Weighted kappa
A measure of the extent to which observers achieve agreement beyond the level expected to occur by chance alone. Kappa can take values from 0 (poor agreement) to 1.0 (perfect agreement).

Whispered voice test
A hearing test in which the examiner stands behind the patient and whispers 3 letters/numbers while gently using the end of his or her finger to occlude and rub the external auditory canal of the patient’s nontested ear. The patient is considered to have passed the screening test if they repeat at least 3 out of a possible total of 6 letters/numbers correctly.

Whooping cough
A cough with a distinctive whooping noise. Also known as pertussis.

Wild-type allele
The allele at a particular SNP that is most frequent in a population, also called “common” allele.

Withdrawing treatment
Discontinuing medical treatment of a terminal disease while the patient continues to receive comfort care.

Wound erythema
Abnormal redness of the skin; considered a classic sign of wound infection.