We used a modified method of SSW-EMLA test described by Ng et al.[21 (link)] First, both hands of the patient were washed using soap and water and dried. The examiner observed the initial appearance of the fingers and photographed them before EMLA 5% cream (lidocaine 2.5% and prilocaine 2.5%; AstraZeneca; Cambridge, United Kingdom) application. A thick covering of EMLA 5% cream was applied to the distal segment of the 2nd, 3rd, and 4th fingers of both right and left hands. Each finger was wrapped in a food grade plastic wrap and sealed using skin bandage. After the application of EMLA cream, the patients were asked to wait for 30 minutes and to keep the hands dry and clean. The patients were not allowed to drink coffee, tea, or smoke cigarettes during the waiting period. If the EMLA application was compromised, the patient waited for an extra hour and the whole procedure was repeated.
When 30 minutes were up, the examiner opened the bandages and examined the skin for wrinkling. The finger-tip appearances were compared with a special scale (Fig. 1) and scored. Wrinkling grades for digits 2, 3, and 4 were counted and average obtained. A difference of ≥3 points per hand (i.e., ≥1 point per digit) was taken as a cut-off or a different score. The SSW-EMLA test was considered abnormal if the total wrinkling score of each hand was <9.
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