URINE NGAL IS AN EARLY PREDICTIVE MARKER OF CONTRAST INDUCED NEPHROPATHY IN PATIENTS WITH NORMAL RENAL FUNCTION UNDERGOING CORONARY ANGIOGRAPHY

Introduction:

Coronary angiography is a frequent cause of contrast induced nephropathy (CIN) amongst various procedures employing use of contrast media. The conventional definition of a 0.3 mg/dl rise in creatinine within 48-72 hours is insensitive and associated with a delayed diagnosis.  As majority of the patients are discharged within 24 hours of an angiogram, biomarkers to predict contrast nephropathy earlier are needed. Neutrophil gelatin associated lipocalin (NGAL) is known to rise as early as 2-12 hours after contrast administration allowing for early detection and monitoring of these patients. There is a paucity of studies assessing the utility of NGAL as an early marker for contrast induced nephropathy in India. 

Methods:

This was a single centre, observational and cross-sectional study done at AIIMS Jodhpur, Rajasthan, India. Eighty patients admitted for elective coronary angiography or percutaneous intervention and having normal creatinine were enrolled from August 2021 to October 2022. We excluded patients having heart failure, sepsis and chronic kidney disease. Urine samples were collected before the angiogram and 8 hours afterward, then centrifuged and stored at minus 80°C. They were then tested for urine NGAL using Elabscience ® Human NGAL ELISA kit as per manufacturer’s instructions. A serum creatinine rise of 0.3mg/dl at 48 hours from the baseline was defined as contrast nephropathy. A cut-off value of urine NGAL for detection of CIN was derived using a ROC curve. 

Results:

Out of 80 patients 50 (67.5%) were males. Median age was 60 years (53.25- 65.00). Sr. Creatinine at baseline was 0.91 mg/dl (0.82-1.01) and median e-GFR as per CKD-EPI was 87 ml/min (79.00- 99.25). Forty-two patients (52.5 %) were diabetics. 6 out of 80 patients (7.5%) developed contrast nephropathy.  Median contrast volume was higher in the CIN group than in the non-CIN group (77.5 ml vs. 50 ml; P = 0.04). Median urine NGAL values at 8 hours after angiogram was significantly higher in CIN group (639.5 ng/ml vs. 160.6 ng/ml; P= 0.003). Median HbA1C values were higher in the CIN group (8.3% vs 6.5%; P = 0.05). HbA1C had a mildly positive correlation with NGAL values post-contrast (rho = 0.287, p = 0.010). Diabetic patients had a higher values of urine NGAL post contrast administration compared to non-diabetics (262.10 ng/ml vs 148.1 ng/ml) Diabetic patients in study had a higher age (58.81 ± 8.66 vs 57.26 ± 13.31; P= 0.048), higher BMI levels (26.45 ± 4.23 vs 24.72 ± 3.55 kg/m2; P = 0.046) and received higher contrast volume (68.21 ± 23.13 vs 58.42 ± 20.23; P = 0.048) compared to the non-diabetic group. The urine NGAL value 8 hours post-angiogram had an AUC of 0.870 [95%CI: 0.752 – 0.989, p=0.003)]. At a cut-off value of 408.75 ng/ml, sensitivity was found to be 83.3 % and specificity was found to be 82.4 %.

 Conclusions:

In our study, a urine NGAL value of 408.75ng/ml at 8 hours post angiogram could predict contrast induced nephropathy. Larger contrast volume and higher HbA1c levels are associated with increased chances of developing contrast nephropathy.

I have no potential conflict of interest to disclose.

I did not use generative AI and AI-assisted technologies in the writing process.