How Reliable Is a MUST Score as Evidence? What Both Sides Should Check in a Malnutrition Claim

A score from the Malnutrition Universal Screening Tool appears in almost every set of hospital records I review in a malnutrition claim. It is usually the first document both sides reach for. The claimant points to a score that was never recorded, or recorded and ignored. The defendant points to a score of zero on admission as evidence that there was nothing to act on.

An earlier article on this site looked at when a missed or wrong MUST score becomes a breach. This one asks the question that comes before it: how much weight can a recorded score actually bear? As an HCPC-registered dietitian instructed in hospital malnutrition cases, I find that the answer depends less on the number than on how it was produced.

Why the question is timely

MUST was launched by BAPEN in 2003 and remains one of the most widely used adult screening tools in the UK. A review published in the British Journal of Nursing in April 2026 set out the current evidence supporting its use and the common challenges in completing it in practice. Its standing in UK practice is not the question here. What is worth revisiting, for anyone relying on a MUST trail in litigation, is what the tool was designed to do and what it was not.

The standard of nutritional care

NICE guideline CG32 on nutrition support in adults expects hospital inpatients to be screened on admission and weekly thereafter, using a tool that takes account of body mass index, unintentional weight loss and the effect of reduced intake. MUST scores three components: a BMI score, a score for unplanned weight loss over the previous three to six months, and an acute disease effect score. The total places the patient at low, medium or high risk, and each band carries a management pathway, from routine rescreening to referral and treatment.

MUST is a screening tool. It identifies who needs a closer look. It is not a nutritional assessment, and a score is not a diagnosis of nutritional status.

Where a score can mislead

In one recurring class of case, a patient with heart failure or liver disease is weighed on admission while carrying significant fluid. The recorded weight is stable, the BMI looks reassuring, and the score is low. Over the following weeks lean tissue is lost while fluid masks the change on the scales. The score was completed, and completed on time, and it understated the patient's risk.

That is the commonest way a MUST trail misleads, but not the only one. Weight and height are sometimes estimated or recalled rather than measured, and BAPEN's own guidance provides alternative measures and subjective criteria for that situation. Amputation, plaster casts and oedema all require adjustment. The acute disease effect score has a narrow definition and is frequently scored wrongly in both directions. MUST is not validated for children or in pregnancy. And weekly screening, by design, cannot capture a patient who deteriorates between screens.

The evidential question

The records that carry the analytical weight are the measured weights themselves, the source of each height, the fluid balance and oedema documentation, the food and fluid charts, and any note explaining why a score was or was not acted on. A score sheet in isolation is rarely enough.

The expert's task is to reconstruct the screen. That means recalculating BMI from the recorded measurements, recalculating weight loss from the actual weight trends, checking whether a limitation such as fluid overload was recognised at the time, and asking whether clinical judgement was layered on top of the score where the tool's own guidance expected it to be. An absent record is itself a finding, though not necessarily proof that care was absent.

What this means for each side

For claimant teams, a low score on a fluid-overloaded or estimated-weight patient is not reassurance, and a score that was correct on its own terms may still have been the wrong question to stop at. For defendant teams, a screen completed correctly, at the right frequency, with documented reasons for the risk band, is strong evidence that the screening limb of the standard was met, even where the patient later became malnourished. Both sides benefit from knowing which of those cases they have before reports are exchanged.

Standard, breach and causation

The standard is judged by what was reasonable at the time, not with hindsight, and in clinical negligence it is assessed against the practice of a responsible body of professional opinion, provided that opinion can withstand logical analysis. Causation in a civil claim is decided on the balance of probabilities, and it turns on separating harm caused or materially contributed to by a nutritional failure from harm that the underlying disease would have caused regardless. A screening failure that would have made no difference to management does not, on its own, establish causation.

What a dietitian should not address

A dietetic expert can say whether the screen was completed correctly, whether the result should have prompted referral, and what nutritional management would have followed. Whether a patient's deterioration was driven by their cardiac, hepatic or oncological disease, and what their prognosis would otherwise have been, belong to the relevant medical experts.

Practical guidance for instructing solicitors

Records to obtain include: every recorded weight and height with its source; the MUST or equivalent screening documentation for the whole admission; fluid balance charts and any oedema assessment; food and fluid charts; and dietetic referrals and responses.

Key instruction questions: Was screening completed on admission and weekly? Was each component scored correctly from reliable measurements? Was any limitation of the tool recognised and documented? Did the result, or clinical judgement, require referral, and was referral made?

Independent dietitian expert witness

I provide independent expert evidence on hospital malnutrition, nutritional screening and dietetic standards of care, for claimant and defendant instructions. If a MUST trail sits at the centre of a matter you are assessing, it is worth a conversation before the screening record is relied on.

Rick Miller BSc., MSc., RD

Consultant Registered Dietitian

HCPC DT25651