The Influence of Thyroid Function, Inflammation, and Obesity on Risk Prediction of Acute Kidney Injury by Cystatin C in the Emergency Department

Abstract

Background/Aims: There is a growing role for emergency departments (ED) in assessing acute kidney injury (AKI) for hospital admissions but there are few studies addressing acute kidney injury biomarkers and confounding factors in the ED. Cystatin C (CysC), a newer renal biomarker, is influenced by thyroid function, inflammation and obesity. This study aims to be the first study to address the impact of these parameters in the ED. Methods: Admitted patients (n=397) were enrolled in the ED at Robert-Bosch-Hospital, Stuttgart, Germany. Daily serum creatinine (sCr) was recorded for AKI classification by Kidney Diseases Improves Global Outcome (KDIGO) criteria. CysC, thyroid stimulating hormone (TSH), thyroxine (T4), C-reactive protein (CRP) and body mass index (BMI) were registered at enrollment in the ED. Serum samples were collected at enrollment, after 6 hours and in the following mornings (day 1 to day 3). The correlation of CysC and sCr was studied on a two variable logistic regression model. A linear predictor was computed to predict minimal AKI stage and area under the curve (AUC) was calculated. Results: Of 397 patients enrolled for classification by KDIGO AKI criteria, n=152 (38%) developed AKI, n=69 (17.4%) reached AKI stage I, n=70 (17.6%) AKI stage II, and n=13 (3%) AKI stage III. Although a correlation between CRP and CysC levels was shown (rho=0.376), this didn't affect the predictive ability for AKI according to our data. We compared receiver operating characteristic (ROC) curves (DeLong test) of CysC to ROC curves of CysC with the additional variables TSH, BMI, and CRP respectively. Our data shows that addition of CRP, TSH, or BMI does not improve prediction of AKI stage beyond prediction based solely on CysC levels. Conclusions: CysC is known to be influenced by thyroid function, inflammation and obesity, but in our large ED population there was no significant impact of these factors on the diagnostic accuracy of CysC to detect AKI in ED patients.

Renal function and delirium in older fracture patients: different information from different formulas?

“…Therefore, we cannot exclude that cystatinbased eGFR might be affected by inflammatory status, in turn influencing its association with delirium. Yet, in an emergency care setting, where patients with acute inflammatory conditions are referred too, the predictive role of cystatin C as estimate of kidney injury was not negatively affected [50]. Fifth, we were able to adjust data for comorbidity, but not for polypharmacy or pain.…”

Estimation of Urinary Creatinine Excretion and Prediction of Renal Function in Morbidly Obese Patients: New Tools from Body Composition Analysis

“…Other formulas, proposed to predict GFR from PCr and other anthropometric data in CKD patients, have not fully validated in severely obese subjects [34, 35]. It is also debated if formulas based on serum cystatin C are more adequate or, to the contrary, may produce a misclassification of CKD stages due to the production of cystatin C by fat cells [36-38]. The inaccuracy in the prediction of UCr from actual body weigth and also from estimated lean body weigth is probably the major cause of error of creatinine based prediction formulas.…”

Serum Cystatin C Predicts AKI and the Prognosis of Patients in Coronary Care Unit: a Prospective, Observational Study

“…However, the receipt of glucocorticoids, thyroid function, inflammation and obesity, rather than sex or age, may affect the measurement of serum CysC[16-18]. Recent studies have further suggested that serum CysC (sCysC) may be an early predictor for AKI and the prognosis of patients in cardiac surgery [19-22], intensive care [23, 24], radiocontrast administration settings [25] and emergency departments [26]. …”