Cryotherapy of viral warts: a sustained 10-s freeze is more effective than the traditional method

Background Cryotherapy is a standard treatment for viral warts. Although textbooks recommend treating until there is a halo of ice around the wart (traditional freeze), many authors advocate more aggressive cryotherapy. There are no previously published studies assessing the efficacy of longer freezing times. Objectives To compare the efficacy of the traditional freeze and a sustained 10-s freeze in the treatment of common viral warts with liquid nitrogen. Methods Patients attending a dedicated wart clinic were randomized to receive either a traditional freeze or a 10-s sustained freeze with liquid nitrogen delivered by a spray gun. Two hundred patients were recruited, 100 in each group. Results After five treatments, 49 patients in the 10-s freeze group were clear of warts (64% of non-defaulters) as compared with 31 (39%) of those in the traditional freeze group (chi (2) = 6.7; P = 0.009). Seventy-four patients in the 10-s freeze group as compared with 59 in the traditional freeze group had either improved or cleared after five treatments (chi (2) = 5.0; P = 0.02). Morbidity was significantly greater in the 10-s freeze group. Sixty-four patients suffered pain or blistering as compared with 44 in the traditional freeze group (chi (2) = 10.8; P = 0.0045). Five patients were withdrawn from the 10-s freeze group because of pain as compared with one patient in the traditional freeze group. Conclusions A 10-s sustained freeze is more effective in the cryotherapy of viral warts but carries a significantly greater morbidity in terms of pain and blistering.