Provocation testing in polymorphic light eruption using fluorescent ultraviolet (UV) A and UVB lamps

Provocation testing is frequently performed during investigation of patients with suspected polymorphic light eruption (PLE). Techniques are not standardized between centres.

We sought to evaluate the efficacy of different fluorescent ultraviolet (UV) radiation lamps for provocation testing in PLE.

We analysed results in 68 patients referred consecutively for phototesting in whom a diagnosis of PLE seemed likely based on clinical history. Patients' case notes were reviewed and responses recorded to provocation testing on forearm skin over three consecutive days using broadband UVA, narrowband and broadband UVB lamps.

A positive papular response to broadband UVA exposure was seen in 38 patients [56%, estimated 95% population confidence interval (CI) 43-67.9]. Thirty-four patients (50%) had a positive papular response to narrowband UVB exposure (95% CI 37.6-62.4). The probability of a positive provocation test following irradiation with both lamps was 80.9% (95% CI 69.5-89.4). From April 1999, 34 patients also had provocation testing with broadband UVB. Although six patients (18%) had a positive papular response, they all showed a positive response to one or both of the other lamp types.

Provocation testing with fluorescent UVA and UVB lamps is a cheap and readily available method that can be used as a diagnostic aid to investigate patients with suspected PLE. Using both broadband UVA and narrowband UVB lamps for testing increases the likelihood of confirming the diagnosis than if either lamp is used alone.