A Large-Scale, Retrospective Analysis of Bath-Psoralen Plus Ultraviolet A Therapy for Psoriasis: A Single-Center Study

Abstract

Background/purpose: While biologics and small-molecule inhibitors are first-line systemic treatments for psoriasis, phototherapy remains an alternative for patients unable to access these treatments because of medical or financial constraints. Narrow-band ultraviolet B (NB-UVB) is effective for localized psoriasis but less so for extensive disease. To address this limitation, bathwater delivery of psoralen plus ultraviolet A (bath-PUVA) was introduced in 2004. This study evaluates the efficacy, safety, and patient characteristics associated with bath-PUVA therapy in a large cohort.

Methods: This retrospective analysis included 229 patients (180 males, 49 females) treated with bath-PUVA from 2004 to September 2021. Baseline characteristics and treatment outcomes were assessed using the psoriasis area and severity index (PASI). Statistical analyses examined relationships between treatment outcomes and factors, including baseline PASI, body mass index (BMI), and smoking status.

Results: The mean baseline PASI score was 24.9. Bath-PUVA achieved PASI 75 in 80.4% of patients, PASI 90 in 44.1%, and PASI 100 in 2.6%, with efficacy comparable to biologics. Patients achieving PASI 90 had significantly higher baseline PASI scores (p = 0.005), while the number of irradiations required did not differ (p = 0.692). Higher baseline PASI scores correlated with elevated BMI (p = 0.002), but BMI did not influence improvement rates (p = 0.094). Smokers had significantly higher baseline PASI scores (p = 0.004) compared with non-smokers, yet smoking status did not affect improvement rates (p = 0.862).

Conclusion: Bath-PUVA demonstrates efficacy comparable with biologics for psoriasis, regardless of BMI or smoking status. This analysis supports its use as an effective and accessible treatment option for patients with extensive disease.

Keywords: bath‐PUVA (bath‐psoralen plus ultraviolet a therapy); phototherapy; psoriasis.

FIGURE 1

(A) Numbers and percentages of patients achieving PASI 75, PASI 90, and PASI 100, indicating PASI achievement. (B) Numbers and percentages of patients with absolute PASI scores of ≤ 3, ≤ 2, and ≤ 1. (C) Numbers and percentages of patients achieving PASI 75, PASI 90, and PASI 100 for each body component. (D) Numbers and percentages of patients achieving PASI 75, PASI 90, and PASI 100 for each PASI component (erythema, induration, and scaling). (E) Numbers and percentages of patients achieving PASI 75, PASI 90, and PASI 100 for each psoriasis subtype. CPP, chronic plaque psoriasis; EP, erythrodermic psoriasis; GP, guttate psoriasis; GPP, generalized pustular psoriasis; PASI, psoriasis area and severity index.

FIGURE 2

(A) BMI and PASI score at hospital admission, PASI improvement rate, and BMI and age of onset. (B) Smoking history, PASI score at hospital admission, and PASI improvement rate. BMI, body mass index; n.s., not significant; PASI, psoriasis area and severity index.

FIGURE 3

(A) Presence or absence of comorbidities and PASI improvement rate. COPD, chronic obstructive pulmonary disease; NAFLD, non‐alcoholic fatty liver disease; PASI, psoriasis area and severity index; PsA, psoriatic arthritis.