Acute kidney injury risk assessment at the hospital front door: what is the best measure of risk?

Abstract

Background: We examined the prevalence of acute kidney injury (AKI) risk factors in the emergency medical unit, generated a modified risk assessment tool and tested its ability to predict AKI.

Methods: A total of 1196 patients admitted to medical admission units were assessed for patient-associated AKI risk factors. Subsequently, 898 patients were assessed for a limited number of fixed risk factors with the addition of hypotension and sepsis. This was correlated to AKI episodes.

Results: In the first cohort, the prevalence of AKI risk factors was 2.1 ± 2.0 per patient, with a positive relationship between age and the number of risk factors and a higher number of risk factors in patients ≥65 years. In the second cohort, 12.3% presented with or developed AKI. Patients with AKI were older and had a higher number of AKI risk factors. In the AKI cohort, 72% of the patients had two or more AKI risk factors compared with 43% of the cohort with no AKI. When age ≥65 years was added as an independent risk factor, 84% of those with AKI had two or more AKI risk factors compared with 55% of those with no AKI. Receiver operating characteristic analysis suggests that the use of common patient-associated known AKI risk factors performs no better than age alone as a predictor of AKI.

Conclusions: Detailed assessment of well-established patient-associated AKI risk factors may not facilitate clinicians to apportion risk. This suggests that additional work is required to develop a more sensitive validated AKI-predictive tool that would be useful in this clinical setting.

Keywords: AKI; acute tubular necrosis; chronic renal failure; chronic renal insufficiency; epidemiology.

Fig. 1.

Age-dependent distribution of AKI risk factors. (A) The average number of AKI risk factors by indicated age groups with the error bars representing the standard deviation. (B) The percentage of patients in each age group with no risk factors and (C) the percentage of the total patient cohort within each age group.

Fig. 2.

(A) Age-dependent distribution of patients at high risk of AKI. High risk of AKI was defined as the presence of two or more fixed patient-related AKI risk factors. (B) Individual AKI risk factor (AKI-R) distribution. (B) Percentage of patients (solid black bars), patients ≥65 years of age (grey bars) or patients <65 years of age (open bars), positive for each of the individual fixed patient-related AKI risk factors. DM, diabetes mellitus; CKD, chronic kidney disease; BP, hypertension; IHD, ischaemic heart disease; CCF, congestive cardiac failure; CVD, cerebrovascular disease; PVD, peripheral vascular disease; Ob, morbid obesity; LD, liver disease; Neuro, neurological or cognitive impairment; AIDS, known diagnosis of AIDS; ACEi, angiotensin converting enzyme inhibitor; D, prescription of diuretic; NSAID, prescription of non-steroidal anti-inflammatory drugs).

Fig. 3.

Distribution of AKI risk factors (AKI-R) in HA- (solid bars) and CA-AKI (open bars). The data are expressed as a percentage of patients from either cohort. For significance, the appropriate P-value is shown. For each risk factor when no P-value is listed, the differences were not statistically significant.

Fig. 4.

Receiver operator characteristic curve for AKI prediction score for the whole cohort of patients using the AKI risk factors excluding age (A) or age alone (B), compared with the HA-AKI cohort using the AKI risk factors excluding age (C) or age alone (D) and the CA-AKI cohort using the AKI risk factors excluding age (E) or age alone (F). Solid line: prediction score, dashed line, reference line.