Abstract: We included 13 RCTs, with a total of 662 participants. We report the results of intention-to-treat analyses (ITT) here. Our primary outcomes of interest were as follows: Participant-rated global improvement, Percentage of participants reaching Psoriasis Area and Severity Index (PASI) 75 (which meant equal to or more than 75% reduction in PASI score), Withdrawal due to side-effects, and Clearance rate. In one RCT of NB-UVB compared with oral PUVA in participants with CPP, the difference in PASI 75 was not statistically significant (risk ratio (RR) 0.91, 95% confidence interval (CI) 0.63 to 1.32; N = 51; low quality). In three other RCTs of CPP, the clearance rates were inconsistent because in one, there was no difference between the groups (RR 1.01, 95% CI 0.91 to 1.12; N = 54), and in the other two, the clearance rates were statistically significantly in favour of oral PUVA: RR 0.66, 95% CI 0.47 to 0.93; N = 93 and RR 0.75, 95% CI 0.59 to 0.96; N = 100, respectively. Pooled data from these three studies indicated that withdrawals due to adverse events were not significantly different between either group (RR 0.71, 95% CI 0.20 to 2.54; N = 247; low quality). The evidence from the comparison of NB-UVB with bath PUVA in terms of clearance rate for CPP was also inconsistent: Pooled data from two left-right body comparison RCTs found no significant difference between the NB-UVB and bath PUVA groups (RR 1.79, 95% CI 0.46 to 6.91; N = 92; low quality), while a parallel RCT favoured bath PUVA (RR 0.18, 95% CI 0.05 to 0.71; N = 36; low quality). In participants with PPP, one RCT found there were no significant differences between NB-UVB treated sides and topical PUVA treated sides in terms of clearance rate (RR 0.09, 95% CI 0.01 to 1.56; N = 50; low quality). Two RCTs found NB-UVB plus retinoid (re-NB-UVB) and PUVA plus retinoid (re-PUVA) had similar effects for treating people with CPP or GP in terms of clearance rate (RR 0.93, 95% CI 0.79 to 1.10; N = 90; low quality). One RCT in people with CPP found no significant differences between NB-UVB and selective BB-UVB in terms of clearance rate (RR 1.40, 95% CI 0.92 to 2.13; N = 100; low quality) and withdrawals due to adverse events (RR 3.00, 95% CI 0.32 to 27.87; N = 100; low quality). No studies reported our primary outcomes for NB-UVB compared with conventional BB-UVB. Current evidence is very heterogeneous and needs to be interpreted with caution. The clearance rate between oral PUVA and NB-UVB is inconsistent among the included studies. Evidence regarding NB-UVB versus bath PUVA is also inconsistent. Re-NB-UVB and re-PUVA are similarly effective for treating people with CPP or GP. In practice, NB-UVB may be more convenient to use since exogenous photosensitiser is not required before phototherapy. NB-UVB is considered ineffective for PPP in clinical practice, and a small RCT did not detect a statistically significant difference between NB-UVB and topical PUVA for clearing PPP. NB-UVB seemed to be similar to selective BB-UVB for clearing CPP. Larger prospective studies are needed to confirm the long-term safety of NB-UVB.

Plain-language summary: This review included 13 small randomised controlled trials (RCT), with a total of 662 participants. Most of these were of poor methodological quality. For treating CPP, the clearance rate between the NB-UVB and oral PUVA groups were inconsistent in three RCTs. In one, there was no difference between the groups, and in the other two, the clearance rate was in favour of oral PUVA. The evidence from the comparison of NB-UVB with bath PUVA in terms of clearance rate was also inconsistent: Pooled data from two left-right body comparison RCTs found no significant difference between the two groups, while another RCT favoured bath PUVA. Two RCTs found NB-UVB plus retinoid (re-NB-UVB) and PUVA plus retinoid (re-PUVA) had similar effects for treating people with CPP or guttate psoriasis. One RCT found no significant differences between NB-UVB and selective BB-UVB for clearing CPP or in the number of withdrawals due to side-effects. In participants with PPP, one RCT found there were no statistically significant differences between NB-UVB treated sides and topical PUVA treated sides in terms of clearance rate. In summary, NB-UVB may be preferred to oral or bath PUVA because it is more convenient to use. NB-UVB seemed to be equal to selective BB-UVB for clearing CPP. Evidence regarding NB-UVB and conventional BB-UVB is limited. The long-term safety of NB-UVB needs to be confirmed. The efficacy of NB-UVB for clearing PPP needs to be confirmed in future studies.