Validation of the Oxford classification of IgA nephropathy

Area of Science:

• Nephrology
• Pathology
• Clinical Medicine

Background:

• The Oxford classification for IgA nephropathy (IgAN) identifies key pathological features for prognosis.
• These features include segmental glomerulosclerosis/adhesion, mesangial hypercellularity, endocapillary proliferation, and tubular atrophy/interstitial fibrosis.

Purpose of the Study:

• To validate the prognostic performance of the Oxford IgAN classification in an independent North American cohort.
• To compare the predictive value of the Oxford classification's pathological elements in both original and validation datasets.

Main Methods:

• Utilized a cohort of 187 adults and children with IgAN from four North American centers.
• Compared the performance of the logistic regression model and individual pathological variables from the original Oxford study.
• Analyzed clinical, laboratory, and histological data, including patient outcomes and therapies received.

Main Results:

• The logistic model demonstrated good predictive performance in the validation cohort (c-statistic 0.75), though slightly lower than the original study (0.82).
• Most pathological variables retained similar predictive value, with mesangial hypercellularity being a weaker predictor in the North American cohort.
• The North American cohort received more immunosuppressive and antihypertensive therapies during follow-up.

Conclusions:

• The North American cohort validates the Oxford IgAN classification, supporting its use in clinical practice.
• Further research is required to understand the impact of treatment on outcomes and refine the prognostic value of mesangial hypercellularity.