Corticosteroids in the treatment of IgA nephropathy: lessons from the TESTING trial.

IgA nephropathy (IgAN), the most common form of primary glomerulonephritis, is mainly observed in young adults and children. Clinical and basic studies indicate the role of immunity in IgAN pathogenesis; however, corticosteroid therapy has been controversial in past decades. The TESTING study, initiated in 2012, is an international, multicenter, double-blinded, randomized, placebo-controlled trial that aimed to evaluate oral methylprednisolone's safety and long-term efficacy under conditions of optimized supportive treatment in patients with IgAN whose risk of progression is high. After a decade of effort, the successful completion of the TESTING study showed that a 6- to 9-month course of oral methylprednisolone is an effective regimen to protect kidney function in high-risk patients with IgAN, but also demonstrated safety concerns. Compared with the full-dose regimen, the reduced-dose regimen was reported to be beneficial, with successfully increased safety. Overall, the TESTING trial provided more data regarding the treatment dosage and safety of corticosteroids, a cost-effective therapy, in IgAN, which have important implications for pediatric patients with IgAN. With a deeper understanding of the disease pathogenesis of IgAN, ongoing studies of novel therapeutic regimens would help further optimize the benefit-risk ratio.