Neutrophil-to-Lymphocyte Ratio May Predict Contrast-Induced Nephropathy

We read with interest the article ‘‘Neutrophil-to-lymphocyte ratio predicts contrast-induced nephropathy in patients undergoing primary percutaneous coronary intervention’’ by Kaya et al. They investigated the relationship between neutrophilto-lymphocyte (N/L) ratio and contrast-induced nephropathy (CIN) in patients with ST-segment elevation myocardial infarction (STEMI). They demonstrated a relationship between N/L ratio and CIN development in patients with STEMI undergoing primary percutaneous coronary intervention. They also demonstrated an independent association between N/L ratio and CIN development in patients with STEMI undergoing coronary angiography. A full blood count is a cheap method that provides information about red and white cells, platelets, count and dimensions of subgroups of cells, and parameters like red cell distribution width, platelet cell distribution width, and mean platelet volume. Routine peripheral blood counts may be useful in risk stratification of patients with CIN. The white blood cell (WBC) count is one of the inflammatory biomarkers. Although the WBC may be within the normal range, subtypes of WBC, as expressed by the N/L ratio, may predict all-cause mortality. The N/L ratio is an easy, cheap, noninvasive, and widely available laboratory marker used to evaluate systemic inflammation. The N/L ratio has received increased attention due to its role as an independent prognostic factor for coronary artery disease (CAD), hypertension, chronic kidney disease, diabetes, heart failure, cerebrovascular disease, peripheral arterial disease, and malignancy. It can also be affected by atherosclerotic risk factors such as smoking, alcohol consumption, hypercholesterolemia, metabolic syndrome, nonalcoholic liver disease, abnormal thyroid function tests, and older age. Furthermore, acute bacterial and viral infections may change the N/L ratio. Additionally, medications such as antihypertensive therapy including angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, b-blockers, and statins may influence the N/L ratio. It would be useful and the results might be different, if the authors described these factors. The CIN is a serious complication of PCI. The CIN is one of the most important reasons of hospital-acquired renal failure. The CIN can cause prolonged hospitalization, increased cost and incidence of renal and cardiovascular events, and mortality. Elderly patients are at greater risk of CIN because of decreased renal reserve. In addition, some factors like glomerular filtration rate (GFR) 200 mL were identified as risk factors for CIN after PCI. Alcohol consumption and arterial blood pressure before contrast exposure may be associated with increased risk of CIN in patients. Hypertriglyceridemia, metabolic syndrome, impaired fasting glucose, and multivessel disease may also be associated with the higher incidence of CIN. Also, some medications including a renin–angiotensin–aldosterone system medications may be related to CIN. Finally, they used the Cockcroft-Gault equation to calculate the GFR. The modification of diet in renal disease (MDRD) is another method for calculating the GFR. However, the Cockcroft-Gault equation may estimate lower GFR in younger age groups compared with the MDRD formula, but it can measure higher GFR in older individuals compared with the MDRD formula. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) recently published an equation for GFR using the same variables (serum creatinine level, age, sex, and race) as the MDRD formula. However, the CKD-EPI equation more accurately categorized individuals with respect to longterm clinical risk of incident end-stage renal disease, all-cause mortality, coronary heart disease, and stroke compared with the MDRD formula. In addition, even mild chronic kidney dysfunction such as a GFR <90 mL/min and dehydration was also a risk factor for CIN. In conclusion, these findings will enlighten further studies about N/L ratio as a surrogate marker of risk stratification in