Department of Dermatology, Aneurin Bevan Health Board, St Woolos Hospital, Newport, U.K.
Br J Dermatol. 2013 Sep;169(3):687-9. doi: 10.1111/bjd.12395.
The traditional method of assessing minimal phototoxic dose (MPD) prior to photochemotherapy with psoralen-ultraviolet A (PUVA) is inconvenient and cannot directly determine PUVA start doses. A handheld minimal erythema dose UVB tester can be modified by fitting a TL-10 UVA compact fluorescence lamp (CFL).
To determine whether MPD testing is possible with a CFL and to calculate a fixed factor to convert observed MPD to PUVA-equivalent MPD.
Patients had two sets of MPD tests performed on symmetrical, contralateral sites on the lower back. MPD test results from a panel of PUVA lamps were compared with MPD from the modified handheld tester. Additionally, a questionnaire survey was completed by 43 U.K. phototherapy units to assess routine practice concerning MPD testing prior to PUVA therapy.
Thirty-seven patients with psoriasis were recruited. Boston phototypes in the 31 with conclusive MPD reactions were: I, four; II, 11; III, 12; and IV, four. The handheld MPD results were linearly related to the PUVA panel MPD results as follows: PUVA MPD = 0·48 × handheld MPD + 0·17 J cm(-2). The measured PUVA MPD was 0·48 of the handheld MPD, not 0·15 as predicted by the published PUVA action spectrum.
The modified MPD tester is a convenient and safe method for PUVA MPD testing, overcoming many problems of the 'traditional method'. The difference between the PUVA and TL-10 lamps was lower than predicted from published studies. This suggests that formal re-evaluation of the erythema action spectrum for PUVA is now needed.
在进行补骨脂素-长波紫外线 A（PUVA）光化学疗法之前，评估最小光毒剂量（MPD）的传统方法既不方便，也不能直接确定 PUVA 起始剂量。可以通过安装 TL-10 长波紫外线紧凑型荧光灯（CFL）来改装手持最小红斑量 UVB 测试仪。
确定使用 CFL 进行 MPD 测试是否可行，并计算将观察到的 MPD 转换为 PUVA 等效 MPD 的固定因子。
患者在背部两侧对称部位进行两组 MPD 测试。比较一组 PUVA 灯的 MPD 测试结果与改装后的手持测试仪的 MPD 测试结果。此外，英国 43 个光疗单位完成了一份问卷调查，评估在进行 PUVA 治疗前进行 MPD 测试的常规做法。
招募了 37 名银屑病患者。在有明确 MPD 反应的 31 名患者中，波士顿光型为：I 型 4 名，II 型 11 名，III 型 12 名，IV 型 4 名。手持 MPD 结果与 PUVA 面板 MPD 结果呈线性相关，如下所示：PUVA MPD = 0.48 × 手持 MPD + 0.17 J cm(-2)。实测的 PUVA MPD 是手持 MPD 的 0.48，而不是文献报道的 PUVA 作用光谱所预测的 0.15。
改装后的 MPD 测试仪是一种方便、安全的 PUVA MPD 测试方法，克服了“传统方法”的许多问题。PUVA 和 TL-10 灯之间的差异低于文献报道的研究结果。这表明现在需要对 PUVA 的红斑作用光谱进行正式重新评估。
