Urinary neutrophil gelatinase-associated lipocalin for early detection of acute kidney injury in geriatric patients with urinary tract infection treated by colistin.

INTRODUCTION: Colistin (polymyxin E) was developed ~ 60 years ago but was rarely used in clinical practice during the last 20 years because of concerns related to high rates of nephrotoxicity. However, it was recently reintroduced to clinical practice in many parts of the world for the treatment of multi-drug resistant gram-negative bacilli. In the current study, we evaluated the predictive capacity of urine neutrophil gelatinase-associated lipocalin (NGAL) for early diagnosis of acute kidney injury (AKI) in geriatric patients with urinary tract infection (UTI) receiving colistin therapy.

METHODS: We studied 116 patients aged 80.7 ± 12 treated with colistin who suffered from UTI. Urinary NGAL was measured at baseline and 1 - 2 hours after the second dose of colistin. The primary outcome was AKI. Secondary outcome was in-hospital morbidity and mortality.

RESULTS: 52 patients (44.8%) developed acute tubular necrosis (ATN) (14% of these had underlying CKD), 8 (7%) had prerenal azotemia, 8 (7%) had stable CKD without changes in renal function during hospitalization and the remaining 48 patients (41%) had normal kidney function. The mean duration of colistin therapy was 9.1 ± 4.8 days. At baseline, urine NGAL was 405 ± 452 g/l in ATN, 285 ± 256 g/l in prerenal azotemia, 390 ± 468 g/l in CKD and 347 ± 877 g/l in normal kidney function patients (difference non-significant). We were unable to demonstrate statistically significant increments of urine NGAL following colistin administration in either ATN or non-ATN patient groups. Urine NGAL was not correlated with urinary leukocyte or erythrocyte counts or baseline comorbidities such as CKD, heart failure, or diabetes. For primary outcome (ATN), receiver operating characteristics curve revealed AUC 0.59 (95% CI 0.49 - 0.7) sensitivity 0.65, and specificity 0.62 for a cutoff value of urinary NGAL 140 g/l. Similar results were obtained for secondary outcomes.

CONCLUSIONS: Our data suggest limited predictive capacity of urinary NGAL for early diagnosis of AKI in a large clinical setting of geriatric patients hospitalized for UTI and receiving the potentially nephrotoxic colistin. This finding is likely due to the powerful influence of UTI on NGAL levels in both patients with normal kidney function and those with a wide spectrum of acute or chronic kidney diseases.