Malnutrition Screening Tools (MUST, MNA)

Malnutrition screening tools identify patients at risk of undernutrition so that full assessment and support can follow. The Malnutrition Universal Screening Tool (MUST) is used across hospital, community and care home settings. The Mini Nutritional Assessment (MNA) is designed for older adults.

Both are quick questionnaires scored from simple measures. They detect risk and do not diagnose malnutrition.

Usage. They are used at hospital admission, in primary care, and in care homes, with repeat screening at intervals.

MUST. Three scores are added. BMI: over 20 kg/m² scores 0, 18.5 to 20 scores 1, and under 18.5 scores 2. Unplanned weight loss over the preceding 3 to 6 months: under 5% scores 0, 5 to 10% scores 1, and over 10% scores 2. Acute disease effect: a score of 2 is added if the patient is acutely ill and there has been, or is likely to be, no nutritional intake for more than 5 days.

MNA short form. Six items covering appetite, weight loss, mobility, acute illness or psychological stress, neuropsychological problems, and BMI (or calf circumference when BMI cannot be measured). The total score is 0 to 14.

Contraindications and precautions. Oedema, ascites and amputation make weight and BMI unreliable, and clinical judgement or alternative measures are used.

Interpretation.

• MUST: a total of 0 is low risk, 1 is medium risk, and 2 or more is high risk.
• MNA short form: 12 to 14 is normal nutritional status, 8 to 11 is at risk of malnutrition, and 0 to 7 is malnourished.
• High risk patients receive a full dietetic assessment and nutritional support.

Causes of a high risk score. Reduced intake from illness, dysphagia, depression or dementia, malabsorption, increased losses, increased requirements, and social factors.

Critical values and findings needing immediate action. A high risk score in a patient with severe weight loss or very low intake requires prompt nutritional support and monitoring for refeeding syndrome.

Limitations and artefacts. Both tools depend on accurate weight and height, which may be unavailable. They do not assess micronutrient status. Screening must be repeated, because risk changes.

Follow up tests. Full dietetic assessment, serum electrolytes, phosphate, magnesium and potassium before and during refeeding, albumin, vitamin and trace element levels, and handgrip strength.

Special groups. Older adults are screened using the MNA. Children are screened using tools designed for paediatric use. Patients with obesity can still be malnourished.