ORIGINAL ARTICLE
Year : 2022 | Volume
: 9 | Issue : 2 | Page : 94--100
Comparison of Nutrition Risk Screening 2002 and Subjective Global Assessment for predicting postoperative complications among patients undergoing elective abdominal surgery
Hemamalini Raghuraman1, M Kavyashree1, Gurushankari Balakrishnan1, TP Elamurugan1, Gomathi Shankar1, Nivedita Nanda2, Mahalakshmy Thulasingam3, Vikram Kate1,
1 Department of Surgery, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
2 Department of Biochemistry, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
3 Department of Preventive and Social Medicine, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
Correspondence Address:
Dr. Vikram Kate
Department of Surgery, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry - 605 006
India
Abstract
Introduction: Malnutrition leads to poor outcomes in surgical patients, leading to negative impact during the postoperative period. Nutrition Risk Screening (NRS) 2002 and Subjective Global Assessment (SGA) are novel tools to assess nutrition risk which have the potential to predict the postoperative complications in surgical patients. Aim: This study was carried out to determine the efficiency of the NRS 2002 and SGA in predicting postoperative complications. Materials and Methods: A prospective cohort study was conducted to assess the nutritional risk of patients aged 18 years and above who underwent elective abdominal surgery. NRS 2002 and SGA were used for nutritional screening. Univariate analysis was carried out to determine the relative risk (RR) of complications for each variable. Receiver operating characteristic (ROC) and area under curve (AUC) were plotted for NRS 2002 and SGA to identify the score for the former and grade for the latter that predicted complications postoperatively. The correlation of malnutrition with surgical outcomes was performed to determine their association. Results: A total of 320 patients were included in the study. Among the patients who underwent elective abdominal surgeries, 39.4% of the total number developed postoperative complications. The most prevalent were Grade 2 complications, which accounted for 69.1% of all such events. Postoperative complications were recorded in 75.5% of the patients identified as at risk by NRS 2002, with a RR of 5.3 (95% confidence interval [CI]: 3.7–7.6; P < 0.001). Complications were found among 68.3% of those who were malnourished by SGA, with a RR of 4.2 (95% CI: 3.0–6.0; P < 0.001). The ROC curve for NRS 2002 to determine the complications had an AUC of 0.80. A score of 3 was the optimal cutoff of NRS 2002 for predicting complications with a maximum sensitivity of 93.6%. Similarly, the ROC curve for SGA grades to determine complications had an AUC of 0.79. Grade B was the best cutoff, with a sensitivity of 77.0%. Conclusion: Patients with NRS 2002 scores higher than or equal to 3 and SGA Grades B and above had a higher incidence of postoperative complications in patients undergoing elective abdominal surgeries. Hence, NRS 2002 and SGA are reliable nutrition risk assessment tools for predicting postoperative outcomes.
How to cite this article:
Raghuraman H, Kavyashree M, Balakrishnan G, Elamurugan T P, Shankar G, Nanda N, Thulasingam M, Kate V. Comparison of Nutrition Risk Screening 2002 and Subjective Global Assessment for predicting postoperative complications among patients undergoing elective abdominal surgery.Int J Adv Med Health Res 2022;9:94-100
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How to cite this URL:
Raghuraman H, Kavyashree M, Balakrishnan G, Elamurugan T P, Shankar G, Nanda N, Thulasingam M, Kate V. Comparison of Nutrition Risk Screening 2002 and Subjective Global Assessment for predicting postoperative complications among patients undergoing elective abdominal surgery. Int J Adv Med Health Res [serial online] 2022 [cited 2023 Mar 21 ];9:94-100
Available from: https://www.ijamhrjournal.org/text.asp?2022/9/2/94/364989 |
Full Text
Introduction
Malnutrition is a ubiquitous concern of public health. It has no universally accepted rationale; nonetheless, commonalities across definitions include an abnormal nutritional condition that leads to variations in body composition and impaired function.[1] Malnutrition includes both undernutrition and overnutrition, yet the terms malnutrition and undernutrition are frequently used interchangeably. It is a worldwide concern with potentially devastating consequences with 20%–50% of hospitalized patients being undernourished, depending on population and pathology.[2] Many studies have reported that 30%–60% of the inpatients in surgical facilities are malnourished.[3] Preoperative malnutrition affects up to two out of every three major surgery patients, a diagnosis that is seldom recognized and treated much less frequently.[4] A multinational observational, cross-sectional, retrospective study in 2021 reported a prevalence of malnutrition between 12% and 78% among patients undergoing abdominal surgeries in Asian countries.[5]
Malnutrition among surgical patients is due to many factors, including inadequate food intake, increased nutrient requirements, unintentional nutritional loss, and inflammation. Surgical stress can additionally exacerbate this catabolic condition.[6] Data from the National Surgical Quality Improvement Program reported that malnutrition is one of the few substantially modifiable preoperative risk factors associated with poor surgical outcomes, including death.[7] Malnutrition leads to poor outcomes in surgical patients. This includes impaired wound healing, increased risk of anastomotic dehiscence and infections. All these lead to an extended hospital stay and associated morbidity. Hence, it negatively impacts the quality of life of surgical patients.
Early diagnosis of patients at risk of malnutrition is crucial, as it helps to initiate preoperative preventive measures for improved postoperative outcomes. Nutritional risk assessment can be done using various screening tools. Nutrition Risk Screening (NRS) 2002 is a novel tool with the advantage of being the first tool developed by evidence-based medicine and includes the current nutritional status and the severity of the disease. A meta-analysis on preoperative nutritional risk assessed by NRS 2002[8] reported that patients with preoperative nutritional risk had higher complication rates, increased mortality, and a longer duration of hospitalization. Subjective Global Assessment (SGA) is reported to be a valid indicator of both undernutrition and hospital outcomes,[9],[10] These tools have been used to predict malnutrition in many hospitalized patients, but only a few studies have used them to evaluate postoperative outcomes. In India, only a handful of studies have utilized nutrition risk assessment to evaluate postoperative complications among patients undergoing elective abdominal surgeries.[8] The present study would be among the few studies to determine the predictive power of NRS 2002 and SGA individually and in combination to predict the postoperative complications in patients undergoing elective abdominal surgery. The study aimed to evaluate the efficiency of the NRS 2002 and SGA in predicting postoperative complications.
Materials and Methods
This study was conducted as a prospective cohort study to assess the nutritional risk of patients who underwent elective abdominal surgery in the department of surgery in a tertiary care hospital in South India.
Study design and study population
The institute's ethics committee approved the study. All patients aged 18 years and above who underwent elective abdominal surgery during the study period (from October 2018 to April 2021) were included sequentially.
Study procedure
All the patients who decided to involve themselves in the study signed an informed consent form. NRS initial screening was performed on all patients at admission, and final screening was performed on patients who answered positively to any initial screening questions. Nutrition risk was also assessed using SGA, anthropometry, and handgrip strength within 48 h of the patient's admission. Demographic data, clinical details, postoperative complications, and length of hospitalization were documented using a structured pro forma. Correlation of malnutrition with surgical outcomes was performed to determine the association between them.
Data collection
The NRS 2002 was segmented into two sections: initial screening and final screening. Patients with an age-adjusted total score of 3 or more were classified as being at risk, whereas patients with a score <3 and patients who did not undergo final screening were classified as not at risk.[11] Based on SGA, each patient was assigned to one of the three categories: Grade A as well nourished, Grade B as slightly malnourished, or Grade C as severely malnourished.[9] Grades B and C were merged as the malnourished group to analyze the tool for diagnostic purposes. The surgeries were classified as major surgery if they involved esophageal, gastric, intestinal, hepatic, and pancreatic resections and as minor surgery if no abdominal organ resections were involved.[12] The Charlson Comorbidity Index (CCI) was used to assess the presence of comorbidities in patients.[13] The CCI total score is the summation of weights, with elevated scores signifying a higher mortality risk and more complicated comorbid illnesses. The primary outcome assessed was the occurrence of postoperative complications until discharge. Clavien–Dindo classification (CDC) was employed for grading the complications.[14] Grades 1 and 2 were categorized as minor complications. Grades 3 and above were categorized as major complications.
Sample size
The NRS 2002 was found to have 81.8% sensitivity for predicting nutrition risk among patients at admission.[15] Based on that, the sample size was calculated using OpenEpi (Open Source Epidemiologic Statistics for Public Health, available at: www.OpenEpi.com) version 3. The sample size was calculated using a 10% confidence limit. The 95% confidence interval (CI) needed 58 patients with postoperative complications. Based on this and assuming a complication rate of 20%, the population size was calculated to be 290. Presuming a 10% nonresponse rate, the final sample size was 320 patients who underwent elective abdominal surgery.
Statistical analysis
Clinical and demographic data recorded as categories were described as absolute frequencies and percentages. The data were subjected to univariate analysis for demographic and clinical variables to find relative risk (RR) along with the 95% CI and P values. Receiver operating characteristic (ROC) along with area under curve (AUC) was plotted for NRS 2002 and SGA to identify the score for the former and grade for the latter that predicted complications postoperatively. Each tool was analyzed separately, and in combination. Two distinct combinations were attempted. One of the combinations was determining the predictive power when both tools indicate at risk or undernourishment in patients versus both tools indicating no risk or undernourishment. The other combination consisted of one of the tools indicating risk or undernourishment versus both tools predicting no risk or undernourishment. The predictive values sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), likelihood ratio, and the ratio of correct classification along with 95% CI were computed separately and in combination for NRS 2002 and SGA. The outcome was recorded as the development or nondevelopment of complications and used as the reference for the ROC curve analysis. All statistical analyses were performed on Stata for Windows, Version 14 (StataCorp LP, College Station, Texas, USA).[16]
Results
The study included 320 patients who underwent elective abdominal surgery. One hundred and twenty-six (39.4%) of the total number of patients who had surgery developed postoperative complications. The demographic features of the study population are detailed in [Table 1]. The mean (standard deviation [SD]) age of patients who had complications was 51.7 (12.8) years, whereas the mean (SD) age of patients who did not have complications was 44.7 (13.3) years. The RR of developing complications was 3.4 (95% CI: 1.6–6.8; P = 0.001) for patients above the age of 60 years, and 2.3 (95% CI: 1.1–4.6; P = 0.020) for patients between the ages of 31 and 60 years. Male patients had an increased risk of having postoperative complications than females (RR: 1.3; 95% CI: 1.0–1.7; P = 0.057).{Table 1}
The distribution of complications based on the Clavien–Dindo classification is shown in [Figure 1]. Only 19% of the complications were major complications (Grades 4 and above), while 81% were minor complications (Grades 3 and below). Mortality was recorded in 3.2% who suffered from complications. The most prevalent complication was Grade 2 complications, which accounted for 69% of all complications.{Figure 1}
The association of clinical parameters with the development of postoperative complications was assessed [Table 2]. Patients who underwent surgery for malignancy had an RR of 3.0 (95% CI: 2.4–3.9; P < 0.001) for developing complications. Conventional surgery had a threefold increased risk of developing complications (RR: 3.0; 95% CI: 2.2–4.0; P = 0.001). The patients who underwent major surgeries had a higher risk of developing complications (RR: 9.0; 95% CI: 5.2–15.7; P < 0.001). Patients who underwent upper gastrointestinal tract surgery had the maximum risk with an RR of 7.4 (95% CI: 3.6–15.3; P < 0.001). This was followed by hepatopancreatic surgeries, which had an RR of 5.1 (95% CI: 2.4–10.7; P < 0.001) for developing postoperative complications. The presence of comorbidities in the patients significantly increased the risk of postoperative complications (RR: 1.7; 95% CI: 1.3–2.1; P < 0.001).{Table 2}
The association between NRS 2002 and SGA with postoperative complications is shown in [Table 3]. NRS 2002 identified 40.9% of the study population as at risk, while SGA identified 44.38% as malnourished. Postoperative complications were recorded in 75.6% of the patients identified as at risk by NRS 2002, with a RR of 5.2 (95% CI: 3.7–7.6; P < 0.001). Complications were found among 68.3% of those who were malnourished as per SGA, with a RR of 4.2 (95% CI: 3.0–56.0; P < 0.001). When the ROC curve was plotted using the NRS 2002 scores for the development of complications, the AUC was determined to be 0.8 (95% CI: 0.7–0.9). A score of 3 was the cutoff of NRS 2002 for predicting complications with a maximum sensitivity of 93.6%, specificity of 62.2%, and accuracy of 80.1%. Similarly, ROC for SGA grades was plotted, and the AUC was found to be 0.79 (95% CI: 0.8–0.8). Grade B was the best cutoff, with a sensitivity of 77% and specificity of 76.8%, with an accuracy of 76.9%. The ROCs are illustrated in [Figure 2].{Figure 2}{Table 3}
The sensitivity of either of the tools predicting risk or undernourishment was 85.7% (95% CI: 78.8–91.0), followed by both tools in combination predicting risk or undernourishment which had a sensitivity of 83% (95% CI: 74.0–89.3). Both tools' prediction in combination had a specificity of 84.2% (95% CI: 78.2–89.1). PPV was highest in the combination of NRS 2002 and SGA with 76.5% (95% CI: 68.1–83.6). The NPV was identical for either of the tools and in a combination of tools with 88.9% (95% CI: 83.3–93.1). PLR was the highest, with 5.3. NLR was nearing equal for both the combinations of the tools for the former and latter combinations. When both tools were used together to predict postoperative complications, it correctly classified 83.8% (95% CI: 67.4–77.2) [Table 4].{Table 4}
The overall rate of mortality in the study group was 1.3%. According to SGA, malnourished patients had a mortality rate of 3.1%, while patients at risk, as classified by NRS 2002, had a mortality rate of 2.8%.
Discussion
The present study showed that 40% of the patients who underwent elective abdominal surgeries developed postoperative complications. Presence of comorbidities and malignancies, conventional methods of surgeries, major surgeries, and those involving the upper gastrointestinal tract were associated with a greater risk of complications. In the present study, NRS 2002 and SGA were used to determine the significance of nutritional risk assessment in predicting postoperative complications. Among the patients identified at risk of malnutrition, those with NRS 2002 score ≥3 and SGA Grades B and above had an increased risk of postoperative complications.
The postoperative outcome of patients undergoing elective surgeries is multifactorial. Age, gender, and comorbidities are nonmodifiable risk factors. In the present study, male gender and patients aged more than 60 years had a higher risk of developing complications. The association of clinical parameters which contributes to increased risk of postoperative complications was assessed. Patients who underwent surgeries for malignancies had two-fold higher risks. Those who underwent conventional surgeries and major surgeries had a higher risk of developing complications. This might be due to prolonged surgical duration and major resections which increase the postoperative morbidity. Similarly, surgeries involving upper gastrointestinal tract also had an increased risk of complications.
Preoperative nutritional state is a significant and modifiable risk factor which greatly affects the postoperative outcome.[17] NRS 2002 and SGA are excellent nutrition tools which identify patients at risk of malnutrition, with higher scores corresponding to increased malnutrition. The NRS 2002 and SGA are used in multiple studies as nutritional screening tools rather than predictors of postoperative outcome.
A meta-analysis by Sun et al. recorded that the overall complications were more frequent in nutritional-risk patients than in nonnutritional-risk patients (pooled odds ratio: 3.1 [95% CI: 2.5–3.9]; P < 0.001).[8] In the present study, patients identified as at risk by NRS 2002 had a higher probability of developing postoperative complications. Many Western studies have shown that the higher the score of NRS 2002, the greater the risk of postoperative complications.[18] In the EFFORT trial, it was observed that with an increase in NRS 2002 score, a stepwise increase in the risk of 30-day mortality was noticed (an adjusted hazard ratio of 1.2).[19] Similarly, in the present study, a higher NRS 2002 score of 3 and above was found to have an increased risk of developing postoperative complications. It was also noticed that an NRS 2002 score of 3 and above had a sensitivity and specificity in predicting postoperative complications. NRS 2002 showed better predictability for postoperative complications when compared with SGA.
Studies using SGA have found that it can independently predict the occurrence of postoperative complications.[20] The risk of postoperative complications increased with increasing grade of malnutrition as detected by SGA. SGA Grade B was associated with a moderate risk of postoperative complications, and Grade C was associated with an increased risk of postoperative complications.[21],[22] Similarly, in the present study, patients identified as undernourished by SGA had a higher probability of developing postoperative complications. In the present study, it was found that a score of Grades B and above had the best cutoff for predicting complications with a high sensitivity and specificity. When compared to NRS 2002, the SGA was found to have lesser sensitivity and specificity in the present study. However, due to the subjective nature of SGA, it is likely that inconsistencies in malnutrition grading are possible.
There are studies which have used SGA and NRS 2002 nutrition tools separately to predict postoperative outcomes. However, to the best of our knowledge, there are no studies that analyzed the diagnostic effectiveness of NRS 2002 and SGA in combination. The combined ability of NRS 2002 and SGA in predicting nutrition risk was assessed for the first time in the present study. In the present study, when either of the tools was positive, the sensitivity was found to be higher in comparison to the combined sensitivity of the tools together. The specificity and other predictive values were lower when compared to the predictive values of both the tools together. This strongly suggests that assessing the patient population with both tools will be more beneficial rather than using just one. Both NRS 2002 and SGA could not predict major postoperative complications (CDC Grades 3–5) with statistical significance. It is plausible that this is related to the lesser number of patients who suffered major complications, owing to insufficient power for analyzing the association between the nutrition tools and the type of complications.
The study is an adequately powered study which has compared not only the diagnostic efficacy of NRS 2002 and SGA individually but also the efficacy of both the tools together. The limitation of the study was that, first, our institute predominantly serves patients from low socioeconomic status, which may have impacted the study's findings. Second, the study did not have enough power to analyze the association between the nutrition tools and the type of complications. Finally, since this was a single-institutional study, a multi-institutional study may be required to corroborate our findings.
Conclusion
The present study highlights the importance of the assessment of preoperative nutrition in determining postoperative outcomes. It suggests NRS 2002 and SGA as reliable and valuable tools in predicting postoperative outcomes. NRS 2002 scores higher than or equal to 3 and SGA Grades B and above were efficient in predicting postoperative complications in patients undergoing elective abdominal surgeries. Conversely, these tools were not efficient enough to differentiate between major and minor complications. Implementation of NRS 2002 and SGA at the time of admission in patients undergoing elective abdominal surgeries will help in the optimization of patients at risk of malnutrition with preoperative nutrition support. This shall help to reduce the incidence of adverse postoperative outcomes.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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