Assessment and Nutrition Diagnosis
Domain 3 tests whether you can gather valid data and convert it into a correctly written nutrition diagnosis - the step most often done sloppily and most often tested.
Assessment categories
The Nutrition Care Process collects five: food and nutrition history, anthropometric measurements, biochemical data/tests/procedures, nutrition-focused physical findings, and client history (the older ABCD mnemonic: anthropometric, biochemical, clinical, dietary).
Tools and their error
24-hour recall - quick, but a single day is unrepresentative and memory-dependent. Food frequency questionnaire - captures habitual intake and ranks people well, but is recall- and list-dependent. Weighed food record - detailed, but reactive (people change intake when recording) and burdensome. Diet history - good for patterns, slow to administer. No method measures intake without error; ask "valid for what purpose?".
Screening versus assessment
Screens - MST, MUST, NRS-2002 in hospital, MNA-SF in older adults, PG-SGA in oncology - flag risk and trigger referral. They are not assessments and do not produce a PES statement.
The PES statement
Format: Problem (standardised terminology and code) related to Etiology as evidenced by Signs/Symptoms. One problem only; the etiology is the cause you can actually intervene on, not the medical diagnosis; signs/symptoms must be measurable and should resolve if the problem resolves.
Weight and BMI
Percent weight change = (usual − current)/usual × 100. Unintended loss >5% in 1 month or >10% in 6 months is clinically significant; >10% in 1 month or >20% in 6 months is severe. BMI = kg/m², but it ignores body composition and fluid shifts.
Worked example
68-year-old man, 1.70 m, weight 60 kg, down from 68 kg in 3 months. Loss = 8/68 × 100 = 11.8% → severe unintentional weight loss. BMI = 60/2.89 = 20.8, which looks "normal" - a deliberate trap. PES: "Unintended weight loss (NC-3.2) related to poor oral intake secondary to dysphagia as evidenced by 11.8% weight loss in 3 months and a 24-hour recall providing ~900 kcal/day." The etiology (dysphagia) is what the intervention must target.
Traps
Writing two problems into one PES; using a medical diagnosis ("diabetes") as the etiology; signs that are opinions ("patient looks thin"); treating albumin or prealbumin as nutrition-status markers when they are negative acute-phase reactants; assuming a normal BMI excludes malnutrition.