Expanding Imaging Classification to Predict Risk of Disease Progression in ADPKD

Patients with autosomal dominant polycystic kidney disease (ADPKD) at highest risk for disease progression are identified using Mayo Clinic imaging classification that uses height-adjusted total kidney volume (htTKV) and age.

However, according to Kyongtae T. Bae, MD, and colleagues, the current Mayo classification is only applicable to patients who have typical disease with diffuse cystic involvement (Class 1) by excluding 5% to 10% of patients (Class 2) with atypical kidney morphology for whom htTKV does not appear to predict decline in estimated glomerular filtration rate (eGFR). Predicting the risk for disease progression in Class 2 patients is uncertain.

The researchers conducted an analysis in a subgroup of patients in the HALT-A study; 21 patients with Class 2 disease with predominant exophytic cyst distribution were included in the analysis. The htTKV of those 21 patients was measured by excluding exophytic cysts to estimate revised htTKV (rev-htTKV). Results of the analysis were reported during a poster session at Kidney Week 2019 in a poster titled Expanded Imaging Classification of Autosomal Dominant Polycystic Kidney Disease (ADPKD).

The outcome of interest was progression to chronic kidney disease (CKD) stage 3, defined as eGFR)<60 mL/min/1.73 m2. For the analysis, the odds ratio of reaching CKD stage 3 per 100 mL/m increment in htTKV were compared in both unadjusted and adjusted logistic models for (1) only Class 1 participants, (2) all participants with original htTKV, and (3) all participants with rev-htTKV. The covariates were baseline age, eGFR, body mass index, sex, and race.

There was a significant association (P<.001) between baseline htTKV and reaching CKD stage 3 in all six logistic models. For both the unadjusted and adjusted models, the estimated odds ratios (ORs) of reaching CKD stage 3 for all participants increased from the use of htTVK to the use of rev-htTKV: the ORs increased from 1.26 to 1.31 in the unadjusted model and from 1.18 to 1.26 in the adjusted model.

The probability of progression to CKD stage 3 decreased for all Class 2 participants because rev-htTKV was always less than htTKV. In addition, the probability of reaching CKD stage 3 for Class 2 participants who did not reach that outcome decreased more than those who did reach CKD stage 3.

“For Class 2 with predominant exophytic cyst distribution, the association between baseline htTKV and CKD stage 3 outcome became stronger with the use of htTKV remeasured after excluding exophytic cysts, compared to the use of original htTKV,” the researchers said.

Source: Bae KT, Shi T, Tao C, et al. Expanded imaging classification of autosomal dominant polycystic kidney disease (ADPKD). Abstract of a poster presented at the American Society of Nephrology Kidney Week 2019 (Abstract TH-PO826), November 7, 2019, Washington, DC.