Formula
PNI = (10 × Albumin g/dL) + (0.005 × Lymphocyte count /mm³)
Example: Albumin 3.5 g/dL, Lymphocytes 1800 /mm³
PNI = (10 × 3.5) + (0.005 × 1800) = 35 + 9 = 44.0
If albumin is reported in g/L, divide by 10 to convert to g/dL before entering, or select g/L from the unit dropdown. Lymphocyte count should be the absolute lymphocyte count (not percentage).
Interpretation
| PNI | Classification | Clinical Implication |
|---|
| ≥ 45 |
Well-nourished |
Low nutritional risk. Acceptable for elective surgery without pre-operative nutritional intervention in most cases. |
| 40–44 |
Mild Risk |
Borderline nutritional status. Consider dietitian referral, oral nutritional supplements, and optimisation before major surgery. |
| < 40 |
High Risk |
Significant nutritional risk. Associated with higher post-operative complications, prolonged hospital stay, and worse oncological outcomes. Pre-operative nutritional support strongly recommended. |
Clinical Application
- Pre-operative nutritional risk: PNI was originally described by Onodera et al. (1984) for gastrointestinal cancer surgery. A PNI < 40 identifies patients at high risk for post-operative complications and should trigger pre-operative nutritional optimisation (enteral supplementation for 7–14 days) before elective major GI resection.
- Oncological outcomes: Multiple meta-analyses in colorectal, gastric, oesophageal, hepatic, and pancreatic cancer confirm that a low pre-operative PNI (<40–45) is an independent predictor of worse overall survival, disease-free survival, and higher recurrence rates after curative resection.
- Surgical complications: PNI predicts anastomotic leak, surgical site infection, respiratory complications, and 30-day mortality in GI surgery. In colorectal cancer surgery, PNI <45 doubles the risk of major post-operative complications.
- Advantages: PNI uses two readily available, inexpensive laboratory parameters. It combines protein status (albumin — affected by inflammation, hepatic synthetic function, and nutritional reserve) with immune status (lymphocyte count — reflects immunocompetence and nutritional state).
- Limitations: Albumin is an acute-phase reactant and falls with inflammation independently of nutritional status. PNI should be interpreted in the context of the clinical picture. In patients with active inflammation or sepsis, pre-albumin or transferrin may supplement the assessment.
- Comparison with other indices: PNI is simpler than the Nutritional Risk Index (NRI) and GNRI, which also incorporate body weight. For comprehensive pre-operative nutritional assessment, PNI should be combined with functional markers (grip strength, performance status) and history-based tools (NRS-2002 or MUST).
References
- Onodera T, Goseki N, Kosaki G. Prognostic nutritional index in gastrointestinal surgery of malnourished cancer patients. Nihon Geka Gakkai Zasshi (Jpn J Surg). 1984;85(9):1001–1005.
- Nozoe T, Ninomiya M, Tanaka T, Matsukuma A, Nakashima H, Ezaki T. Prognostic nutritional index: a tool to predict the biological aggressiveness of gastric carcinoma. Surg Today. 2010;40(5):440–443.
- Sun J, Wang D, Mei Y, et al. Value of the prognostic nutritional index in patients with colorectal cancer undergoing curative surgery. J Investig Med. 2016;64(7):1198–1203.
- Weimann A, Braga M, Carli F, et al. ESPEN guideline: clinical nutrition in surgery. Clin Nutr. 2017;36(3):623–650.