Background/Purpose: Henoch-Schönlein purpura nephritis (HSPN) is the main and almost the only cause of morbidity and mortality among children suffering from this most common vasculitis in childhood. Several classifications are used in the analysis of renal biopsies in HSPN, but it is unknown which one has the strongest association with the severity and outcome. The aim of the study was to compare the four most commonly used histological classifications for HSPN to determinate which one is the best predictor of disease outcome and to establish which variables of each histological classification have the strongest association with unfavorable outcomes.

Methods: The cross-sectional study included 69 patients with HSPN (diagnosed by EULAR/PRES/PRINTO criteria) and available renal biopsy specimens for analysis using 4 histological classifications for HSPN (the International Study of Kidney Disease in Children (ISKDC) classification, the Oxford classification, the Haas histologic classification of IgA nephropathy and the modified semi-quantitative classification (SQC), developed by Koskela et al.). The clinical outcome was defined through 4 categories, graded according to the modified classification of Counahan (physical examination, hematuria, proteinuria, urine albumin-to-creatinine ratio, hypertension and eGFR). The linear relationships between outcome and histological classifications were analysed using ordinal regressions using the first-order of polynomial orthogonal contrasts.

Results: The SQC classification proved to be the best, reducing the deviation (of the model-predicted outcome value from the observed value) by 9.5% (Χ²₁=13,89, p < 0,001), followed by the Oxford classification with a deviation reduction of 8.0% (Χ²₁=11,76, p = 0,001), then the ISKDC classification with a decrease in deviation of 3.3% (Χ²₁=4,89, p = 0,027), and the worst was the Haas classification with a decrease in deviation of 2.1% (Χ²₁=3,06, p = 0,080). Analysis of individual variables of Oxford and SQC classifications showed that with increasing values in the variables of interstitial fibrosis (t₆₆ = 3,23, p = 0,002), tubular atrophy (t₆₆ = 2,94, p = 0,005) and tubular dilatation (t₆₆ = 2,40, p = 0,019) in the SQC classification, and endocapillary hypercellularity (t₆₆ = 3,14, p = 0,003) and crescents (t₆₆ = 2,07, p = 0,043) in the Oxford classification the outcome worsens.

Conclusion: The pilot study showed that the SQC classification, developed by Koskela et al., has the strongest association with the severity and outcome of HSPN, followed by the Oxford classification, while other classifications are less related to the outcome of the disease. Although crescents on renal biopsy were considered the most important outcome indicators, this pilot study suggests that tubulointerstitial changes could be even more important as predictors of poor outcome. Histological changes in the interstitium and renal tubules of HSPN patients should be further explored in order to have an even better predictive value in terms of disease outcomes and to be incorporated into existing or new classifications, on the basis of which guidelines for the treatment of patients would be developed.

SUPPORT: Croatian Science Foundation project IP-2019-04-8822.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/henoch-schonlein-purpura-nephritis-different-histological-classifications-but-which-one-is-most-strongly-associated-to-the-outcome-of-the-disease-pilot-study-of-the-paediatric-rheumatology-european/