3.1 Patient-Generated Subjective Global Assessment (PG-SGA)

Patient-Generated Subjective Global Assessment (PG-SGA)

The Patient-Generated Subjective Global Assessment (PG-SGA), adapted by Dr. Faith Ottery from the original Subjective Global Assessment (SGA) developed by Detsky et al., is universally recognized as the gold-standard tool for nutritional screening, assessment, and triage in oncology. Unlike generic screening instruments designed for general medical-surgical populations (e.g., MUST or NRS-2002), the Scored PG-SGA specifically addresses the unique metabolic, physiological, and symptom-driven challenges faced by cancer patients. It captures both patient-reported subacute changes and clinician-evaluated tissue wasting, providing a continuous quantitative score for longitudinal tracking as well as a discrete qualitative categorization of nutritional status.

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Historical Context & Validation in Oncology

Traditional nutritional assessment tools relied heavily on static laboratory markers (such as serum albumin or transferrin) or simple anthropometric measurements (such as body mass index). However, in oncology, systemic inflammation, fluid shifts, and tumor mass frequently confound these traditional metrics. The PG-SGA was created to overcome these limitations by combining subjective clinical history with objective physical examination signs.

Validation studies across diverse oncology populations—including patients with gastrointestinal, head and neck, lung, gynecologic, and hematologic malignancies in both ambulatory chemotherapy units and acute inpatient wards—demonstrate that the Scored PG-SGA possesses high construct validity, inter-rater reliability, and predictive value. High PG-SGA scores strongly correlate with prolonged hospital stays, increased chemotherapy toxicity, reduced treatment tolerance, diminished quality of life, and shortened overall survival.

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Structure of the Scored PG-SGA

The PG-SGA comprises two operational sections: a 4-part Patient-Completed Component (Boxes 1–4) and a 3-part Clinician-Completed Component (Worksheets 1–3 and Physical Exam).

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|                         SCORED PG-SGA ARCHITECTURE                   |
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| PATIENT-COMPLETED SECTION (Boxes 1-4)                                 |
|  - Box 1: Weight History (1-month & 6-month % loss, 2-week trend)     |
|  - Box 2: Food Intake (changes vs. normal, current diet texture)      |
|  - Box 3: Nutrition-Impact Symptoms (past 2 weeks, weighted 1 to 3 pts)|
|  - Box 4: Work & Functional Capacity (ECOG/Karnofsky correlation)      |
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| CLINICIAN-COMPLETED SECTION (Worksheets 1-3 & Physical Exam)          |
|  - Worksheet 1: Disease & Relation to Nutritional Requirements        |
|  - Worksheet 2: Metabolic Demand (fever, steroids, catabolic stress)  |
|  - Worksheet 3: Physical Exam (fat loss, muscle wasting, fluid/edema) |
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1. Patient-Completed Component (Boxes 1–4)

The first section is designed to be completed directly by the patient or their caregiver in the waiting room or at the bedside, fostering patient engagement and early symptom identification.

Box 1: Weight History

• Current Weight and Height: Establishes baseline parameters.
• Usual Weight (1 Year Prior): Used to compute long-term weight change.
• Weight 6 Months Ago and 1 Month Ago: Captures weight loss velocity.
• Point Allocation for 1-Month Weight Loss:
  • $<1%$ weight loss = $0$ points
  • $1% - 1.9%$ weight loss = $1$ point
  • $2% - 2.9%$ weight loss = $2$ points
  • $3% - 4.9%$ weight loss = $3$ points
  • $\ge 5%$ weight loss = $4$ points
• Recent 2-Week Weight Trend: Adds $1$ point if the patient is currently losing weight or keeping weight the same, and $0$ points if gaining weight.

Box 2: Food Intake

• Evaluates overall intake compared to normal (unchanged, more than usual, or less than usual).
• Identifies current intake patterns: normal solid food (0 pts), solid food but less than normal (1 pt), full fluid diet or oral nutrition supplements (2 pts), clear fluids only (3 pts), taking very little of anything / NPO (4 pts), tube feeding or parenteral nutrition (0 pts if meeting full estimated needs).

Box 3: Nutrition-Impact Symptoms

Evaluates barriers to oral intake present over the past 2 weeks. Symptoms are differentially weighted based on their clinical impact on intake:

Box 4: Work and Functional Capacity

Assesses physical activity and functional performance over the past month:

• 0 Points: Normal activity with no restriction; capacity to perform all pre-disease activities.
• 1 Point: Not my normal self, but able to be up and about with light activity.
• 2 Points: Able to do little activity; spend less than half the day in bed or chair.
• 3 Points: Pretty much bedbound; spend more than half the day in bed or chair.

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2. Clinician-Completed Component (Worksheets 1–3 & Physical Exam)

The health professional (Registered Dietitian, Nurse, or Physician) reviews the patient's medical record, calculates metabolic stressors, and performs a targeted physical examination.

Worksheet 1: Disease and Relation to Nutritional Requirements

• Scores underlying oncologic diagnoses, cancer staging (e.g., metastatic disease), surgical trauma, and high-risk comorbidities.
• Assigns $1$ point for each major high-risk diagnosis or stress factor (e.g., stage IV solid tumor, head and neck cancer, pancreatic cancer, esophageal cancer, recent major abdominal surgery).

Worksheet 2: Metabolic Demand

Evaluates metabolic stress factors that elevate resting energy expenditure (REE):

• Fever Duration and Height: No fever = 0 pts; $<38.3^\circ\text{C}$ ($101^\circ\text{F}$) for $<72$ hrs = 1 pt; $38.3^\circ\text{C} - 38.8^\circ\text{C}$ for $72$ hrs = 2 pts; $>38.8^\circ\text{C}$ ($102^\circ\text{F}$) for $>72$ hrs = 3 pts.
• Corticosteroid Dose: No steroids = 0 pts; low dose ($<10$ mg prednisone equiv/day) = 1 pt; moderate dose ($10 - 30$ mg/day) = 2 pts; high dose ($>30$ mg/day) = 3 pts.

Worksheet 3: Physical Examination

Evaluates body composition across 3 specific anatomical domains:

1. Loss of Subcutaneous Fat Stores: Inspected and pinched at the orbital fat pads under the eyes, triceps skinfold, and ribcage/mid-axillary line.
2. Muscle Wasting: Palpated and inspected at the temporalis (temples), clavicles (pectoralis major/deltoids), interosseous muscles (hands), quadriceps (thighs), and gastrocnemius (calves).
3. Fluid Accumulation / Edema: Assessed for ankle/pedal pitting edema, sacral edema, and abdominal ascites.

• Each domain is scored qualitatively as Normal ($0$), Mild ($1$), Moderate ($2$), or Severe ($3$). Points are aggregated into a composite physical exam score.

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Numerical Scoring & Clinical Triage Matrix

The total numerical PG-SGA score is the sum of Boxes 1–4 plus Worksheets 1–3. This score directly mandates clinical triage protocols:

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PG-SGA Global Categorization

In addition to the numerical score, the clinician synthesizes all subjective and objective data to assign a qualitative PG-SGA Global Category:

• Stage A (Well-Nourished): Stable body weight or recent intentional weight gain; no significant loss of muscle mass or subcutaneous fat; score generally low ($<4$); active functional capacity.
• Stage B (Suspected or Moderately Malnourished): Unintentional weight loss of $5% - 10%$ within 6 months; mild-to-moderate loss of muscle mass and subcutaneous fat; persistent nutrition-impact symptoms; progressive functional decline.
• Stage C (Severely Malnourished): Severe unintentional weight loss ($>10%$ in 6 months or $>5%$ in 1 month); severe skeletal muscle wasting and loss of fat stores; visible fluid retention/edema; severe functional impairment or bedbound status.

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Comprehensive Worked Clinical Case Study

Patient Scenario

A 62-year-old male with Stage IIIb Squamous Cell Carcinoma of the Base of Tongue undergoing concurrent chemoradiation therapy (Week 4 of 7) presents for oncology nutrition assessment.

• Anthropometrics: Current weight = $68\text{ kg}$, Usual weight = $76\text{ kg}$ (6 months ago), Weight 1 month ago = $72\text{ kg}$. Height = $178\text{ cm}$ (BMI = $21.5\text{ kg/m}^2$).
• Intake & Symptoms: Patient reports taking only full fluids and oral nutrition supplements ($2$ pts). Reports severe radiation mucositis/mouth sores ($2$ pts), pain ($3$ pts), dry mouth ($1$ pt), and altered taste ($3$ pts). Total Box 3 score = $9$ pts.
• Function: Spends most of the day sitting, able to perform light activities ($1$ pt).
• Clinician Assessment: Metastatic head and neck cancer ($1$ pt). Receiving low-dose dexamethasone ($10\text{ mg/day}$) for radiation edema ($2$ pts). Physical exam reveals moderate temporal and clavicular muscle wasting ($2$ pts) and mild triceps fat loss ($1$ pt).

Scoring Calculation

1. Box 1 (Weight History): Weight loss in past month = $[(72 - 68) / 72] \times 100 = 5.56%$ (Score = $4$ pts). Weight loss in past 2 weeks = losing weight (Score = $1$ pt). Total Box 1 = $5$ pts.
2. Box 2 (Intake): Full fluids / oral supplements (Score = $2$ pts).
3. Box 3 (Symptoms): Mucositis ($2$) + Pain ($3$) + Xerostomia ($1$) + Dysgeusia ($3$) = $9$ pts.
4. Box 4 (Function): Light activity (Score = $1$ pt).
5. Worksheet 1 (Disease): Stage III HNC (Score = $1$ pt).
6. Worksheet 2 (Metabolic Stress): Steroid therapy ($2$ pts).
7. Worksheet 3 (Physical Exam): Muscle/Fat loss (Score = $3$ pts).

Total Numerical PG-SGA Score: $5 + 2 + 9 + 1 + 1 + 2 + 3 = 23$.

Clinical Triage & Action Plan

• Numerical Triage: Score $23 \ge 9$ $\rightarrow$ Critical Need for Immediate Interdisciplinary Intervention.
• Global Category: Stage C (Severely Malnourished) due to $>10%$ 6-month weight loss ($10.5%$) and moderate physical muscle wasting.
• Intervention Plan: Immediate referral for prophylactic enteral tube feeding (gastrostomy tube placement), aggressive multimodal analgesia for mucositis pain, and oral mucosal rinses.