The U.K. Working Party's Diagnostic Criteria for Atopic Dermatitis II. Observer variation of clinical diagnosis and signs of atopic dermatitis

The level of agreement between 14 physicians as to what constitutes a case of atopic dermatitis was tested on 15 selected patients with a range of diagnoses. Between-observer agreement was good, with a mean pair agreement index (P₀) of 0.94, and a chance corrected index (κ) of 0.78. Between- observer agreement in the recording of 18 separate physical signs of atopic dermatitis was then tested by asking the 14 physicians to note the presence or absence of each sign in a different group of patients to those seen in the first part of the exercise. Substantial between-observer agreement (κ>0.61) was only present for truncal dermatitis. Most signs showed only fair to moderate agreement (κ0.21–0.60), and some signs, such as keratosis pilaris, xerosis, orbital pigmentation, fine hair, and extensor dermatitis, showed poor agreement (κ0.01–0.20). The findings were similar when the responses of two independent observers from the national study outlined in Paper I were compared for each sign. Within-observer variation for the recording of physical signs was substantially better than between-observer variation. Physicians interested in atopic dermatitis agree reasonably well on what constitutes a typical case of atopic dermatitis. Between-observer variation with regard to some physical signs of atopic dermatitis is of a magnitude which argues against their continued use in clinical and epidemiological studies.