Formula
GNRI = [14.89 × Albumin (g/dL)] + [41.7 × (Weight / IBW)]
If current weight ≥ IBW, use 1.0 in place of (Weight / IBW)
IBW (Lorentz formula):
Male: IBW = 22 × (Height in metres)²
Female: IBW = 21 × (Height in metres)²
The albumin component captures protein-energy nutritional status, while the weight-to-IBW ratio reflects somatic protein and fat store depletion. When actual weight equals or exceeds IBW, the ratio is capped at 1.0 to avoid artificially elevating the score in obese patients who may still be nutritionally at risk.
IBW Calculation (Lorentz Method)
The Lorentz formula for IBW used in GNRI differs from the Devine formula used in pharmacokinetic contexts. It is based on body mass index and uses sex-specific optimal BMI values:
- Male IBW: 22 × (height in metres)² — based on a target BMI of 22 kg/m²
- Female IBW: 21 × (height in metres)² — based on a target BMI of 21 kg/m²
Example: A male patient 170 cm tall: IBW = 22 × (1.70)² = 22 × 2.89 = 63.6 kg
Interpretation
| GNRI Value | Risk Category | Clinical Recommendation |
|---|
| ≥ 98 |
No Nutritional Risk |
No specific nutritional intervention; routine monitoring |
| 92 – 97.9 |
Low Nutritional Risk |
Dietary counselling; oral nutritional supplementation; reassess in 4 weeks |
| 82 – 91.9 |
Moderate Nutritional Risk |
Formal dietitian referral; consider enteral supplementation; closer follow-up |
| < 82 |
High Nutritional Risk |
Urgent nutritional intervention; multidisciplinary team involvement; consider enteral or parenteral support |
Clinical Application
The GNRI was originally developed and validated for use in elderly hospitalised patients, and has since been extended to numerous clinical scenarios:
- Post-operative outcomes in the elderly: GNRI < 92 is an independent predictor of postoperative morbidity, prolonged hospital stay, and in-hospital mortality following major abdominal surgery in patients aged > 65 years.
- Cardiac surgery: Pre-procedural GNRI stratifies 30-day and 1-year mortality risk following cardiac operations and transcatheter aortic valve implantation (TAVI) in elderly cohorts.
- Gastrointestinal malignancy: GNRI has been validated as a prognostic marker in gastric, colorectal, and pancreatic cancers, with GNRI < 92 correlating with reduced overall survival and higher complication rates.
- Chronic kidney disease: GNRI predicts all-cause and cardiovascular mortality in haemodialysis patients, complementing conventional biochemical markers.
- Limitations: GNRI may be less reliable when albumin levels are acutely depressed due to inflammation (negative acute-phase reactant) rather than true malnutrition. Pre-albumin or CRP co-measurement may help contextualise results.
References
- Bouillanne O, Morineau G, Dupont C, et al. Geriatric Nutritional Risk Index: a new index for evaluating at-risk elderly medical patients. Am J Clin Nutr. 2005;82(4):777–783.
- Cereda E, Pedrolli C, Zagami A, et al. Nutritional screening and mortality in newly institutionalised elderly: a comparison between the geriatric nutritional risk index and the mini nutritional assessment. Clin Nutr. 2011;30(6):793–798.
- Yamada K, Furuya R, Takita T, et al. Simplified nutritional screening tools for patients on maintenance hemodialysis. Am J Clin Nutr. 2008;87(1):106–113.
- Kuzuya M, Izawa S, Enoki H, et al. Is serum albumin a good marker for malnutrition in the physically impaired elderly? Clin Nutr. 2007;26(1):84–90.