Using the Cochrane Library, Medline, and EMBASE, the author analyzed the literature to determine the duration of follow-up needed to assess long-term risk of renal impairment after Henoch-Schönlein purpura (HSP). Of the 34 studies retrieved, only 12 met the criteria for use (previously normal renal function, timed follow-up, presence/absence of renal involvement). The 12 reports were from Europe, the United States, East Asia, the subcontinent of Asia, and the Middle East and included 1,133 children. Across the studies, follow-up ranged from 6 weeks to 36 years. Nearly 66% of the children had normal urinalysis throughout the follow- up period, while 34% had hematuria and/or proteinuria (H/P). Among the children with H/P, 80% had only isolated hematuria or proteinuria, and 20% demonstrated evidence of nephritis (hematuria with 1 or more of the following: elevated serum urea or creatinine, hypertension, or oliguria) or nephrotic syndrome (nephrotic range proteinuria >40μ/m2/hour or 50μ/kg/24 hours with or without edema or hypoal-buminemia). When H/P occurred, 85% of patients developed it within 4 weeks of diagnosis, 91% of patients developed it within 6 weeks, and 97% developed it within 6 months. No patient with normal urinalysis at follow-up developed renal impairment (abnormal creatinine). The risk of developing renal impairment when a patient had only isolated hematuria or proteinuria was very low (1.6%). If a patient developed nephritis or nephrotic syndrome, the risk of renal impairment increased to 19.5%, with females 2.5 times more likely to be in the renal impairment group.
The author concludes that all patients with HSP should have urinalysis and blood pressure measurements at diagnosis and with each recurrence. If hematuria and/or proteinuria are discovered, serum urea and creatinine levels should be followed for up to 6 months after diagnosis. Follow-up beyond 6 months is required for those with continued isolated hematuria or proteinuria. If nephrotic syndrome or nephritis appears, immediate pediatric nephrology consultation is warranted, and continued long-term follow-up is appropriate.
Dr. Aldous has disclosed no financial relationships relevant to this commentary.
A “representative and well-defined sample of patients at a similar point in the course of the disease” is the first validity criterion for studies of disease prognosis.1 The author’s insistence on studies of unselected patients is key to the usefulness of this review. While the diagnostic definition of HSP in the individual studies is not discussed, the clinical picture of the disease is distinctive enough that misclassification is unlikely to be a major problem. The onset of HSP is acute and generally dramatic enough to warrant medical attention, so the timing of diagnosis can reasonably be assumed to be similar across studies. The search strategy used was explicit and appropriate. The main limitations of the review were the variability among studies in reporting the timing of outcomes and the relatively short follow-up...