Preoperative nutritional risk assessment in predicting postoperative outcome in patients undergoing major surgery.

INTRODUCTION: Although a variety of nutritional indices have been found to be valuable in predicting patient outcome when used alone, there is no consensus on the best method for assessing the nutritional status of hospitalized patients. Therefore, the aim of this study was to assess the nutritional status of a cohort of patients who underwent major elective surgery using the Nutritional Risk Index (NRI), Maastricht Index (MI), Subjective Global Assessment (SGA), and Mini Nutritional Assessment (MNA) to determine the best possible nutrition screening system in surgical practice.
METHODS: The study population consisted of 460 patients who underwent major elective surgery between December 1999 and March 2002. Each patient had a complete set of the three nutritional assessment techniques (NRI, MI, SGA); in addition, the MNA was performed in patients older than 59 years of age. One of the coauthors who was unaware of the nutritional assessments assessed the patients for postoperative morbidity and mortality. Complications were classified as major or minor and as infectious or noninfectious. To assess the predictive value of the assessment techniques, likelihood ratios were calculated for the various strata of each method. The odds ratio and receiver operating characteristic (ROC) curves were also calculated to describe and compare the diagnostic value of each of the four nutrition indices.
RESULTS: Twenty patients died during the study period. No complications occurred in 329 of the 460 patients; 42 patients suffered from two or more complications. The frequency of malnutrition was found to be 58.3%, 63.5%, and 67.4% as assessed by the SGA, NRI, and MI, respectively. Morbidity rates, especially severe infectious and noninfectious complications, were significantly higher in malnourished patients in all nutritional indices. The likelihood ratio was well correlated with the risk categories of every nutritional index. The area under the ROC curves revealed that each scoring system proved to be significantly powerful in predicting the morbidity (infectious and noninfectious severe morbidity) and mortality. However, no differences were detected among the nutritional indices in 460 patients. The odds ratio for morbidity between the well nourished and malnourished patients was 3.09 [95% confidence interval (CI), 1.96-4.88], 3.47 (95% CI, 2.12-5.68), 2.30 (95% CI, 1.43-3.71), and 2.81 (95% CI, 0.79-9.95) for the SGA, NRI, MI, and MNA, respectively. All indices except the MNA were significantly predictive for morbidity. The odds ratios were not statistically different among the indices.
CONCLUSIONS: Our findings revealed that all nutritional assessment techniques can be safely applied to the clinical setting with no significant difference in predictive value. We therefore strongly recommend the use of any of these techniques to improve the outcome of surgical care. Meanwhile, further investigations are needed, and much effort must be given to find the best method for assessing nutritional status.