3.2 Nutrition Assessment (ABCD)

The ABCD Framework

Nutrition assessment collects, verifies, and interprets data to identify nutrition-related problems, comparing each finding to a comparative standard (a reference value such as the DRI or a growth percentile). The data are organized into four classic categories plus client history:

• A — Anthropometric: height, weight, BMI, body composition, waist circumference, growth measures
• B — Biochemical: laboratory values and medical tests
• C — Clinical: physical exam findings, medical/surgical history, medications, functional status
• D — Dietary: food and nutrient intake, feeding patterns, supplement use, food access

No single category stands alone — the RD synthesizes all four. For example, a low albumin (B) means little without weight trend (A), an inflammatory clinical picture (C), and actual intake (D). An expected exam skill is performing the anthropometric calculations by hand under time pressure.

Assessment also requires comparing each datum to a standard and a baseline. A serum potassium of 3.2 mEq/L is meaningful only against the reference range (≈3.5-5.0 mEq/L) and the patient's trend. The RD likewise distinguishes a sign (objective, observed by the clinician — edema, low albumin) from a symptom (subjective, reported by the patient — nausea, early satiety); both feed the diagnosis.

A frequent exam framing asks which category a finding belongs to, so practice sorting: weight and BMI are Anthropometric; potassium and HbA1c are Biochemical; temporal wasting and dysphagia are Clinical; a 24-hour recall and supplement list are Dietary.

A — Anthropometric Calculations

Body Mass Index (BMI)

BMI is weight relative to height squared:

BMI = weight (kg) / [height (m)]²

Ideal Body Weight (IBW) — Hamwi Method

• Women: 100 lb for the first 5 ft + 5 lb per inch over 5 ft
• Men: 106 lb for the first 5 ft + 6 lb per inch over 5 ft

Apply a ±10% range for frame size. %IBW = (actual weight / IBW) × 100. A worked case: a man 5 ft 10 in tall → 106 + (10 × 6) = 166 lb IBW; if he weighs 200 lb, %IBW = 200/166 × 100 ≈ 120%. Watch unit traps — convert pounds to kilograms (÷ 2.2) and inches to meters (× 0.0254) before any metric formula.

Percent Weight Change

Unintentional weight loss is one of the strongest single indicators of nutrition risk and a core malnutrition criterion:

% weight change = [(usual weight − current weight) / usual weight] × 100

Worked example: usual weight 80 kg, current 72 kg over 3 months → (80 − 72)/80 × 100 = 10% loss, which clearly exceeds the severe 3-month threshold of >7.5%. A common trap is putting current weight in the numerator's first position — always subtract current from usual, and divide by usual weight. Edema or ascites can mask true loss, so corroborate with the clinical exam.

B — Biochemical (Lab) Markers

Lab values support but do not by themselves diagnose malnutrition; current AND/ASPEN criteria explicitly de-emphasize visceral proteins because inflammation and fluid shifts lower them independent of intake.

Other high-yield labs: hemoglobin/hematocrit and ferritin (iron status — ferritin is also an acute-phase reactant), HbA1c (≈3-month average glucose, diagnostic ≥6.5%), BUN and creatinine (renal/protein), serum electrolytes, and the lipid panel. On the exam, pair a low prealbumin with an elevated CRP and the answer is usually "inflammation present — interpret cautiously," not "protein-energy malnutrition confirmed."

C — Clinical and D — Dietary

Clinical data come from the medical record and a nutrition-focused physical exam (NFPE): muscle wasting (temporal, clavicle, quadriceps), subcutaneous fat loss (orbital, triceps), edema, oral/skin/hair changes, swallowing ability, GI symptoms, and functional status such as handgrip strength by dynamometer.

Dietary intake can be measured several ways, each with trade-offs the exam loves to contrast:

For a single quick snapshot choose the 24-hour recall; to characterize habitual intake over months, choose the FFQ; for the most accurate inpatient data, choose direct observation.