The Malnutrition Screening Tool (MST): Scoring and Next Steps

The Malnutrition Screening Tool (MST) is a quick, two-question check used across Australian hospitals, aged care and community services to spot people who may be at risk of malnutrition. It was developed in Australia in 1999 and takes a minute or two. This guide explains the questions, how each answer is scored, what a score of 2 or more means, how accurate the tool is, and what should happen next. It is written for nurses, support workers, carers and families as well as anyone checking their own risk.

The two questions and how they are scored

Add the two scores together. “Recently” usually means the last six months or so. For example, someone who has lost about 4 kg without trying (1 point) and has been eating poorly because of a poor appetite (1 point) scores 2, which means they are at risk.

What the score means

• Score 0 or 1: not at risk right now. The standard MST form advises monitoring weight and screening again weekly, or in line with local policy.
• Score 2 or more: at risk of malnutrition. The form advises monitoring food intake, using strategies to improve it, and referring to a dietitian or following local policy.

Hospitals set their own timing. For example, Canberra Health Services screens adults within 8 hours of admission, then weekly and whenever their condition changes, and an at-risk result may lead to a dietitian assessment with a validated tool such as the Patient-Generated Subjective Global Assessment (PG-SGA).

How accurate is the MST?

The MST was developed with 408 adult patients at an Australian hospital and checked against a full nutrition assessment. Different staff scoring the same patient agreed 93 to 97% of the time, and later reports describe a sensitivity and specificity of 93%. It has since been tested in other settings, including people having radiotherapy (it identified everyone who was malnourished, although it also flagged some who were not) and residents in long-term aged care, where it performed better than the short form of the Mini Nutritional Assessment when both were compared with a full nutrition assessment in one study. In 2020 the Academy of Nutrition and Dietetics recommended the MST for screening adults regardless of age, medical history or setting.

No screen is perfect. A 2023 study of older hospital patients found that five common screening tools, including the MST, missed a substantial share of people who met diagnostic criteria for malnutrition. Clinical judgement still matters: if someone looks unwell, is eating little or their clothes have become loose, act on it even if the score is low.

Common mistakes when using the MST

• Counting intentional weight loss. The question is about weight lost without trying.
• Not following up “unsure”. An unsure answer scores 2. Look for signs such as looser clothes, a tighter belt notch or dentures that no longer fit.
• Overlooking people in larger bodies. People who are overweight can be malnourished too, and must not be overlooked.
• Relying on weight or BMI alone. In an Australian aged care study, BMI and weight loss alone missed many residents who were malnourished.
• Treating the score as a diagnosis. It is a screen. Diagnosis needs a full assessment.

Screening is not diagnosis

Internationally, malnutrition is diagnosed with the GLIM criteria in two steps: screen with a validated tool such as the MST, then assess. Diagnosis needs at least one physical sign (weight loss, low body mass index or reduced muscle mass) and one cause (reduced food intake or absorption, or inflammation or disease).

Malnutrition in aged care and disability support

Malnutrition is common and often missed. The Nutrition Care Day Survey found 32% of 3,122 patients in 56 Australian and New Zealand hospitals were malnourished, and a 2024 study of 10 Australian aged care homes found 40% of residents were malnourished. The strengthened Aged Care Quality Standards include regular malnutrition screening and responding to the risk of malnutrition, and European guidelines recommend that all older people are routinely screened. Dietitians Australia has called for mandatory screening and quarterly rescreening in aged care. For people supported in their homes or in supported independent living, regular screening by support staff is a simple way to catch problems early.

When to see a doctor

Unexplained weight loss always deserves a medical check as well as a dietitian review. Contact the person’s GP promptly if they have lost weight quickly without trying, have stopped eating or drinking, have trouble chewing or swallowing, or seem more unwell, confused or weak.