Screening tools for malnutrition, with BMI cut-offs for Asians

Nutrition care in older people works in two steps: first screen everyone with a validated tool to find those at risk, then assess those at risk to diagnose malnutrition and grade its severity (GLIM).

GLIM accepts any validated screening tool and names examples including NRS-2002, the MNA short form and MUST.

Mini Nutritional Assessment short form (MNA-SF): designed for older adults. It covers weight loss over 3 months, reduced intake, mobility, psychological stress or acute illness, neuropsychological problems and BMI. Maximum 14 points; 7 or less suggests malnutrition and 11 or less risk of malnutrition.

Malnutrition Universal Screening Tool (MUST): BMI, unplanned weight loss over 3–6 months, and acute illness with no intake for more than 5 days. Maximum 6 points; 2 or more is high risk and 1 is medium risk.

Malnutrition Screening Tool (MST): unplanned weight loss over 6 months and reduced appetite. Maximum 5 points; 2 or more is positive.

Short Nutritional Assessment Questionnaire (SNAQ): weight loss in the past month, reduced appetite and use of supplements or tube feeding. Maximum 7 points; 3 or more suggests malnutrition and 2 moderate risk.

Patient-Generated Subjective Global Assessment short form (PG-SGA-SF): developed for cancer; weight, intake, symptoms and activity. Maximum 35 points; 9 or more suggests malnutrition.

Nutritional Risk Screening 2002 (NRS-2002): a hospital screening tool, also named by GLIM.

Accuracy: in older hospital patients assessed against GLIM, the standard cut-offs missed 32–68% of those with malnutrition. More sensitive cut-offs found 66–89%, best with the PG-SGA-SF and MNA-SF; an MNA-SF cut-off of 11 or less was suggested for older patients.

South Asians often have a “thin–fat” phenotype, with more body fat than Europeans at the same BMI, so lower cut-offs are used. The Endocrine Society of India classifies adults as follows:

Underweight: below 18.5 kg/m²

Normal: 18.5–22.9 kg/m²

Overweight: 23–24.9 kg/m²

Obesity grade 1: 25–29.9 kg/m²

Obesity grade 2: 30–34.9 kg/m²

Obesity grade 3: above 35 kg/m²

By comparison, the international WHO cut-offs for adults are 25 kg/m² or more for overweight and 30 or more for obesity.

The same guideline adds waist circumference above 90 cm in men and 80 cm in women, and notes that BMI is not the best measure in Indians; where BMI is used, use the lower Asian cut-offs.

For diagnosing malnutrition, GLIM's low-BMI threshold in Asia is below 18.5 kg/m² under 70 years and below 20 at 70 or older, compared with below 20 and below 22 elsewhere. GLIM notes that consensus reference BMI data for Asians are still needed.

With age, lean mass falls while fat mass rises, so a stable weight or normal BMI can hide muscle loss. Weigh people repeatedly and look at the trend.

A positive screen is not a diagnosis: follow it with a full assessment, look for the cause, and plan treatment.