We conducted a retrospective analysis included 213 ICU admission due to acute kidney injury. This is the first study in literature evaluating the effects of NLR predicting the outcome, mainly evaluating mortality, in AKI population. As a result we have demonstrated that insulin required diabetes mellitus (2.18, 1.08-4.4; p=0.030, data not shown), infection related AKI, decreased albumin levels, CVD history inotrope usage and aging were mortality predictors. We also showed that, increment in serum creatinine level and timely changed NLR were also independent mortality predictors in mutually adjusted multivariate logistic regression analysis.
Incidence of AKI in worldwide is steadily increasing. AKI associates directly with longevity of hospital duration, patients increased rate of mortality and development or progression of preexistent kidney disease 9. Therefore, AKI has great socioeconomic and public health burden. Ischeamia-reperfusion injury, sepsis and nephrotoxicity are the leading cause of this entity. Especially in elderly population, as in our cohort population, sepsis is the leading cause of all AKI cases 10-16.
After polytrauma, major surgical procedures or sepsis, marked neutrophilia and a lymphocytopenia are well known laboratory abnormalities. Correlation between the severity of clinical course and the grade of neutrophilia and lymphocytopenia is well established in clinical settings 17. Sepsis is the leading cause of AKI and carries high mortality rates. Increased generalized inflammation and inflammation in kidney during sepsis are not surprising. From that point of view it has been reported that the kidney endothelial cells and tubular cells play an active role in inflammatory process 18. Recent studies have demonstrated that inflammation-based prognostic scores are useful in predicting cardiovascular risk. An easy measurable laboratory test, NLR, was also reported in various cardiovascular diseases. The association between NLR and mortality has been showed previously in coronary artery diseases, coronary calcification scores, arterial stiffness, myocardial infarction, cerebrovascular accidents and cardiac syndrome X 19-26. NLR was also examined in patients with renal failure. More recently increased NLR, above the median value, has been shown as a cardiovascular and overall mortality predictor in maintenance peritoneal dialysis patients 27. In hemodialysis patients NLR was also correlated patients mortality. Median value >5/1 was associated mortality significantly as compared to value <5/1 28.
Final NLR and increment in timely changed NLR during hospital stay were significantly correlated with mortality. There was a steadily increment in NLR values compared to the ones pointed at baseline, final and last follow-up particularly in mortal patients. Indeed we observed that, there were lowest NLR value recordings in alive patients, as compared to value of deceased patients on admission. This seems to be important, NLR change during hospital course may be a screening tool for patients outcome. Above the median value, 10/1, as compared to value <10/1 was significantly better mortality predictor. ROC analysis revealed cut-off value for final NLR is 9.90 which had 73% sensitivity and 87% specifity. Change in NLR timely and change in percentage NLR as compared to baseline were also significant predictors of mortality. These were the first detected NLR values predicting mortality in AKI.
MPV and Lymphocyte count change during ICU course are the novel tools for predicting mortality 29,30. Our study has also showed that final MPV and Lymphocyte counts were mortality predictors. Although this relationship has not reached a statistical significance in multivariate regression analysis, this might be clear in larger retrospective populations or prospective designs. Besides NLR, MPV and lymphocyte counts are also cheaper and easily measurable laboratory values which may reflect patients outcome.
There are several limitations. This is the pilot study which is performed on retrospective cohort evaluating the impact of NLR on predicting the mortality rate in AKI. Single center experience which can result in selection bias is another point of view. Our institute has seven ICU affiliations such as Anesthesiology and Reanimation, Chest Disease, Cardiology, Cardiovascular Surgery, General Surgery and Emergency Department ICUs. Highly selected population, representing only internal medicine ICU admissions, were evaluated. Therefore, it is important to realize that our findings may not be applicable to all ICU patients suffering from AKI due to the other types of causes. We only considered the development of AKI on admission rather than the development of AKI later in the hospital course. Patients were examined during ICU stay and until six months after hospital discharge. This scenario may represent the limited patients and time interval for analyzing outcome predictors of AKI. Under the scope of this point of view, we started the analysis of whole ICU population retrospectively and intend to prepare a prospective design in the future.