Risk prediction for acute kidney injury in acute medical admissions in the UK

BACKGROUND: Acute Kidney Injury (AKI) is associated with adverse outcomes; therefore identifying patients who are at risk of developing AKI in hospital may lead to targeted prevention. AIM: We undertook a UK-wide study in acute medical units (AMUs) to define those who develop hospital-acquired AKI (hAKI); to determine risk factors associated with hAKI and to assess the feasibility of developing a risk prediction score. DESIGN: Prospective multi-centre cohort study across 72 AMUs in the UK. METHODS: Data collected from all patients who presented over a 24-h period. Chronic dialysis, community-acquired AKI (cAKI) and those with fewer than two creatinine measurements were excluded. Primary outcome was the development of h-AKI. RESULTS: Two thousand four hundred and fourty-six individuals were admitted to the seventy-two participating centres. Three hundred and eighty-four patients (16%) sustained AKI of whom two hundred and eighty-seven (75%) were cAKI and ninety-seven (25%) were hAKI. After exclusions, chronic kidney disease [Odds Ratio (OR) 3.08, 95% Confidence Interval (CI) 1.96-4.83], diuretic prescription (OR 2.33, 95% CI 1.5-3.65), a lower haemoglobin concentration and elevated serum bilirubin were independently associated with development of hAKI. Multi-variable model discrimination was only moderate (c-statistic 0.75). CONCLUSIONS: AKI in AMUs is common and associated with worse outcomes, with the majority of cases community acquired. Only a small proportion of patients develop hAKI. Prognostic risk factor modelling demonstrated only moderate discrimination implying that widespread adoption of such an AKI clinical risk score across all AMU admissions is not currently justified. More targeted risk assessment or automated methods of calculating individual risk may be more appropriate alternatives.