Two new studies by the same British research team may help to clarify how acute kidney injury (AKI) influences progression of chronic kidney disease (CKD), according to reports presented at the European Renal Association-European Dialysis and Transplant Association 53rd Congress in Vienna.

Researchers led by Nicholas M. Selby, MD, of Royal Derby Hospital in Derby, UK, presented 3-year outcomes from pilot studies preceding the AKI Risk in Derby (ARID) study, a prospective case-control study in a generalized hospitalized population. One pilot study looked at post-AKI risk factors for CKD progression and found that male gender, diabetes, and decline in renal function at 3 months independently predicted an increased likelihood of CKD progression at 3 years. The other study demonstrated that even mild episodes of AKI are associated with CKD progression, although few patients reach end-stage renal disease within 3 years.

The risk factor study included 194 patients with a median age of 71 years and mean baseline estimated glomerular filtration rate (eGFR) of 62.6 mL/min/1.73 m2. Of these patients, 138 (71.1%) had AKI stage 1, 31 (16%) had AKI stage 2, and 25 (12.9%) had AKI stage 3. Ninety-one patients (46.9%) had pre-existing CKD and 41 (21%) had diabetes.

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At 3 years, CKD progression occurred in 39 patients (24.7%). Progressors included a significantly higher proportion of men than women (33% vs 12.5%) and a significantly higher proportion of diabetics (45.7% vs 17%). The progressors also were significantly older (74 vs 70 years).

In multivariable analysis, male gender and diabetes were independently associated with 2.9 times and 5.2 times increased odds of CKD progression at 3 years, respectively. In addition, compared with patients who had a 5.22 mL/min/1.73 m2 or greater increase in eGFR at 3 months, those who had an 8.20 mL/min/1.73 m2 or greater decrease in eGFR at 3 months had a significant 28 times increased odds of progression.

Results also showed that recurrent AKI was associated with ongoing CKD progression.

Dr Selby and his colleagues concluded that non-recovery of renal function at 3 months is an important predictor of CKD progression and evaluation at 3 months could be a useful time point as which to perform a patient risk assessment.

For the other study, Dr Selby’s team identified hospitalized patients with AKI (cases) and without AKI (controls) and matched 300 case-control pairs according to age and baseline eGFR stage. Of the 300 cases, 70%, 16%, and 14% had AKI stage 1, 2, and 3, respectively. The mean eGFR was significantly lower in the AKI group than controls at 3 and 12 months and 3 years. CKD progression was significantly more common in the AKI group than controls at 3 years (23.8% vs 6.8%). The researchers observed the same trend when only pairs with stage 1 AKI were examined: CKD progression at 3 years occurred in 23% of cases compared with 8.2% of controls.

AKI occurred significantly more frequently in the AKI than control group during the 3-year follow-up. The investigators observed no significant difference in the proportion of cases and controls experiencing CKD progression between 3 months and 3 years.

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Proteinuria and albuminuria occurred significantly more frequently in the AKI group than the control group. At 3 years, 50.7% of cases had albuminuria versus 21.1% of controls. The median albumin-creatinine ratio was significantly higher in the AKI patients at 3 years (1.8 vs 0.9 mg/mmol).

Only 2 patients in the AKI group (1.3%) and 3 in the control arm (2%) progressed to a pre-defined renal endpoint (requirement for renal replacement therapy, eGFR less than 15 mL/min/1.73 m2, or doubling of serum creatinine). In addition, 20 AKI patients (13.3%) died compared with 16 (10.7%) in the control group. These between-group differences were not statistically significant.