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IgA nephropathy (IgAN) represents the most reported glomerulonephritis in adults and has a significantly variable risk for progression to end-stage kidney disease. The International IgAN Prediction Tool (IIgAN-PT) predicts the risk of a 50% decline in eGFR or occurrence of ESRD. Its major limitation is it only measures risks using clinical variables collected during the time of biopsy and warrants evaluation of risk after a period of supportive care. This tool was updated and externally validated in 2022 and used clinical variables obtained at a landmark time of 1 or 2 years after biopsy, which yielded improved prediction performance. Majority of the subjects from the validation study by Barbour et al came from Caucasian and East Asian race. Using the updated IIgAN-PT model on a Filipino cohort would provide information on its discriminatory ability to predict ESRD or eGFR decline among IgAN patients from Southeast Asian descent.
This is a retrospective cohort comparing the computed risk at 2, 3 and 5 years using the IIgAN-PT at the time of biopsy vs. a landmark time of one-year post biopsy. Three outcomes were defined: (1) ESRD or >50% decline in eGFR, (2) >50% decline in eGFR, (3) ESRD. Biopsy-proven IgAN patients from 2016-2019 were included. Those with eGFR <15 or who underwent dialysis before biopsy and up to the landmark time of one year were excluded in the study. Clinical variables used in computing risk scores include age, gender, race, level of proteinuria, eGFR, blood pressure, MEST score, use of ACEi/ARB and immunosuppression. C-statistic was used to measure discriminatory power, while Hosmer and Lemeshow test for the calibration. The two predictive tools will be compared using the method of Delong et al with a level of significance at 5%.
A total of 146 patients were included in the study. The mean age was 35.7 with slight female preponderance (56.2%). Their mean eGFR, systolic and diastolic blood pressure at the time of biopsy vs. one-year after were comparable. Statistical difference was noted in the degree of proteinuria (p 0.0001), use of ACEi/ARB (p 0.001) and use of immunosuppression (p 0.001). Mean eGFR (ml/min/1.73m2) at 2, 3 and 5 years were 68.8, 64 and 59.6 respectively. Whereas median UTPCR (mg/g) at 2, 3 and 5 years were 505, 520 and 519 respectively. The discriminatory ability of IIgAN PT at the time of biopsy vs. landmark time were comparable at two years (p 0.253). Notably, at three years (p 0.0217) and five years (p 0.0461), using IIgAN PT at the landmark time of one-year post biopsy is better in predicting the risk of >50% decline in eGFR and progression to ESRD.
The International IgAN Prediction tool when used at the landmark time of one year post biopsy, compared to at the time of biopsy, can better predict the risk of eGFR decline or progression to ESRD at three- and five-years from histologic diagnosis in Filipino patients with IgA nephropathy.