Narrowband ultraviolet B phototherapy does not influence serum and red cell folate levels in patients with psoriasis

BackgroundNarrowband ultraviolet (UV) B phototherapy (nbUVB) is a widely used modality in the treatment of psoriasis and is generally accepted to be safe in pregnancy. Previous studies have described photodegradation of serum folate after exposure to UVA radiation but the effect of UVB is not known. Insufficient folate levels predispose to neural tube defects in pregnancy. In addition, folate deficiency may increase the risk of colorectal carcinoma and influence serum homocysteine levels, which are thought to be a risk factor for cardiovascular disease.ObjectiveWe sought to determine whether exposure to nbUVB reduces folate levels.MethodsThis single-center, open observational study was conducted in a teaching hospital setting. Serum and red cell folate levels were measured in patients with psoriasis attending for nbUVB at baseline and after a minimum of 18 exposures.ResultsA total of 35 patients completed the study. Mean serum and red cell folate levels at baseline were 6.34 and 410 ng/ml, respectively. After nbUVB, mean serum and red cell folate levels were 6.35 and 423 ng/ml, respectively. This was not significantly different from baseline measurements (P = .99 serum folate and P = .57 red cell folate).LimitationsThis study examined the effect of a standard course of 18 exposures of nbUVB on folate levels, rather than prolonged treatment. Adult patients with psoriasis only were investigated.ConclusionA standard course of nbUVB does not have an effect on serum and red cell folate levels in patients with psoriasis.