Comparison of a semiautomated hand‐held device to test minimal erythema dose before narrowband ultraviolet B phototherapy with the conventional method using matched doses

Abstract

A semiautomated hand-held device has been introduced in some phototherapy centres to establish the minimal erythema dose (MED) before treatment with narrowband ultraviolet (NBUV) B. To compare the semiautomated hand-held device with the conventional method of MED testing (a UV-opaque template and a panel of UVB fluorescent tubes), using the same series of incremented doses. Twenty-four patients referred for treatment with NBUVB phototherapy were included. Each patient had MED testing with the conventional method and the semiautomated hand-held device at the same level of the left and right back. The results were read by four investigators each time. The semiautomated hand-held device was a significant estimator of the MED using the conventional panel method (P < 0.001; r = 0.97). The average ratio of the hand-held MED to the conventional MED was 67%. The mean difference between the methods was 165 mJ/cm(2) . The interobserver test showed very high agreement for both methods of MED testing (Cronbach α coefficient 0.97 for the hand-held MED tester vs. 0.93 for the conventional method). The semiautomated hand-held device MED results were lower than that of the conventional panel method and may prolong the treatment course by 2-3 treatments. The hand-held tester is a fast and reproducible method, and may allow more phototherapy units, limited by staff and time, to do MED testing.