[Polychromatic phototest sensibility is superior to UVA phototest in polymorphic light eruptions]

The phototest is used to confirm the diagnosis of polymorphous light eruption and to evaluate the different treatments. The different light sources in the different countries explains the lack of standardization. In France, we use a polychromatic source emitting a radiation close to the solar spectrum. The study compared the efficacy of a polychromatic source with a UVA source in the photo-induction of lesions.

Sixty-four patients presenting with a polymorphous light eruption were selected by a dermatologist. Polychromatic and UVA phototests were performed on each patient. At day 8, the phototest was considered positive if there were papules.

Polychromatic and UVA phototests were positive in respectively 56 p. 100 and 23 p. 100 of the patients. Forty-one per cent of the patients had both polychromatic and UVA negative phototests.

Polychromatic phototest seems to be more sensitive than UVA phototest. Induction of the lesions with a polychromatic source is so easy that it proves the significant role for UVB in the genesis of polymorphous light eruption. The percentage of negative phototests is identical to those published in the literature. Negative phototests are not necessarily secondary a bad methodology, they can individualize patients with those lower photosensitivity who present with a polymorphous light eruption that may resolve spontaneously.