Abstract: Thirteen studies (1403 enrolled patients) were identified. Risks of bias attributes were frequently poorly performed. Low risk of bias was reported in six studies (50%) for sequence generation (selection bias) and in seven (58%) for allocation concealment (selection bias). Blinding of participants and personnel (performance bias) and of outcome assessment (detection bias) was at low risk of bias in three studies. Five studies reported complete outcome data (attrition bias) while eight studies reported expected outcomes so were at low risk of reporting bias. Eight studies evaluated therapy to prevent persistent kidney disease in HSP. There was no significant difference in the risk of persistent kidney disease any time after treatment (5 studies, 746 children: RR 0.74, 95% CI 0.42 to 1.32), or at one, three, six and 12 months in children given prednisone for 14 to 28 days at presentation of HSP compared with placebo or supportive treatment. There were no significant differences in the risk of persistent kidney disease with antiplatelet therapy in children with or without kidney disease at entry. Heparin significantly reduced the risk of persistent kidney disease by three months compared with placebo (1 study, 228 children: RR 0.27, 95% CI 0.14 to 0.55); no significant bleeding occurred. Four studies examined the treatment of severe HSP-associated kidney disease. Two studies (one involving 56 children and the other involving 54 adults) compared cyclophosphamide with placebo or supportive treatment and found no significant benefit of cyclophosphamide. There were no significant differences in adverse effects. In one study comparing cyclosporin with methylprednisolone (15 children) there was no significant difference in remission at final follow-up at a mean of 6.3 years (RR 1.37, 95% CI 0.74 to 2.54). In one study (17 children) comparing mycophenolate mofetil with azathioprine, there was no significant difference in the remission of proteinuria at one year (RR 1.32, 95% CI 0.86 to 2.03). No studies were identified which evaluated the efficacy of therapy on kidney disease in participants with recurrent episodes of HSP. There are no substantial changes in conclusions from this update compared with the initial review. From generally low quality evidence, we found no evidence of benefit from RCTs for the use of prednisone or antiplatelet agents to prevent persistent kidney disease in children with HSP. Though heparin appeared effective, this potentially dangerous therapy is not justified to prevent serious kidney disease when fewer than 2% of children with HSP develop severe kidney disease. No evidence of benefit has been found for cyclophosphamide treatment in children or adults with HSP and severe kidney disease. Because of small patient numbers and events leading to imprecision in results, it remains unclear whether cyclosporin and mycophenolate mofetil have any roles in the treatment of children with HSP and severe kidney disease.

Plain-language summary: This review identified 13 studies (1403 participants) investigating interventions for either preventing persistent HSP-associated kidney disease or treating severe kidney disease. Five studies (856 enrolled children) which compared prednisone tablets given for 14 to 28 days with placebo tablets or no specific treatment for the prevention of persistent kidney disease at 6 to 12 months after onset of HSP. No significant reduction in the frequency of persistent kidney disease was demonstrated. Two studies (129 children) showed no benefit of aspirin and dipyridamole (antiplatelet agents) to prevent persistent kidney disease. One study (228 children) suggested that heparin given by injection could reduce the risk for persistent kidney disease but this treatment has the potential side effect of severe bleeding so its administration is not justified when only one third of children develop any kidney disease and in most this is not serious and resolves completely. There appeared to be no serious side effects in these studies but information provided on side effects was limited. In patients with serious kidney disease, two studies (one in adults and one in children) showed that cyclophosphamide was no more effective than placebo or supportive treatment in preventing progressive kidney injury. Two small studies comparing cyclosporin with methylprednisolone/prednisone (15 children) and mycophenolate mofetil with azathioprine (17 children) found no significant benefits of cyclosporin or mycophenolate. However the numbers of children studied were too small to completely exclude a benefit so further studies are required. No serious side effects were reported. There are few data from randomised controlled studies examining interventions used to prevent or treat serious kidney disease in HSP except for short-term prednisone to prevent kidney disease. There was no evidence of benefit of short courses of prednisone in preventing serious kidney disease in HSP.