New guidelines on diagnosing and treating childhood-onset lupus nephritis (cLN) with a goal of achieving complete renal response recommend excluding orthostatic proteinuria in patients suspected of childhood-onset systemic lupus erythematosus (cSLE) by collecting first morning urine sample (Ann Rheum Dis; 2017; doi:10.1136/annrheumdis-2017-211898). Developed by a panel of 16 expert members as part of the Single Hub and Access point for pediatric Rheumatology in Europe initiative, the guidelines are based on evidence from 55 eligible studies, 23 of which focused on diagnosis. There was 100% agreement among panel members on all six diagnostic recommendations, which all had 3 or 4 level of evidence and C or D strength of evidence, meaning they were extrapolated from randomized controlled studies or extrapolated from expert opinion.
The guidelines define mild proteinuria as urine protein:creatinine (UP:CR) ratio 50-100 mg/mmol and proteinuria as either UP:CR ≥50 mg/mmol or ≥0.5 g/24 hours. Proteinuria or impaired estimated glomerular filtration rate (eGFR)—defined as <80 mL/min/1.73 m2, calculated using the modified Schwartz formula—should prompt consultation with a pediatric nephrologist about the need for biopsy.
Within 6 to 12 months after starting treatment, patients should have partial renal response, defined as ≥50% reduction in proteinuria to “at least subnephrotic levels” and normal or near-normal renal function. Studies included in the panel’s deliberations did not show degree of proteinuria at baseline to be a statistically significant predictor of renal function deterioration in patients with membranous cLN, so the authors did not consider it as a decisive factor for specific treatment strategies.
The authors defined complete renal response from early morning urine sample as either UP:CR <50 mg/mmol or urine albumin:creatinine ratio <35 mg/mmol and eGFR >90 mL/min/1.73m2.