3.2 Subjective Global Assessment (7-Point SGA) in Dialysis

Subjective Global Assessment (7-Point SGA) in Dialysis

Core Clinical Principle: The 7-Point Subjective Global Assessment (SGA) is the bedside tool that KDOQI 2020 recommends as valid and reliable for assessing nutritional status in adults on dialysis (statement 1.5.1, grade 1B). Unlike static laboratory markers that fluctuate with systemic inflammation, the 7-point SGA integrates longitudinal medical history with hands-on physical examination to deliver a highly predictive, semi-quantitative measure of somatic protein and energy stores.

Originally developed by Detsky and colleagues (1987) for general surgical patients, the original SGA classified individuals into three broad categories: Class A (Well-nourished), Class B (Moderately malnourished), and Class C (Severely malnourished). While effective in acute surgical triage, this 3-tier system lacked the granularity needed to detect subtle nutritional shifts, early catabolic declines, or gradual improvements resulting from targeted medical nutrition therapy in chronic kidney disease.

To address this limitation, the CANUSA Peritoneal Dialysis Study Group and KDOQI adapted the instrument into a 7-point Likert scale (where 1 indicates the most severe malnutrition and 7 represents a robustly well-nourished state). This 7-point continuum provides exceptional clinical sensitivity for tracking longitudinal nutritional trajectories in both maintenance hemodialysis (HD) and peritoneal dialysis (PD) populations.

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1. Medical & Weight History Components

The medical history component of the 7-point SGA evaluates five distinct domains, capturing the chronicity and metabolic severity of nutritional insult:

A. Weight Change and Trajectory

Weight history must be interpreted with extreme clinical rigor in dialysis:

• Assessment of Post-Dialysis Dry Weight: Dietitians must evaluate changes in prescribed dry weight (post-hemodialysis weight or empty-abdomen weight in PD) rather than pre-dialysis weights. Interdialytic weight gains (IDWG) from fluid retention or occult volume expansion can completely mask severe underlying muscle and fat loss.
• Six-Month Net Change: Net percentage loss over the preceding 6 months is calculated: [(Usual Dry Weight - Current Dry Weight) / Usual Dry Weight] * 100. Loss < 5% is considered minor; 5% to 10% is moderate; > 10% is severe.
• Acute Two-Week Trajectory: The clinician determines the directional momentum of weight over the past 2 weeks: actively continuing to lose, stabilized, or actively gaining. A patient who lost 8% over 6 months but has gained 1.5 kg of true somatic weight over the past 2 weeks receives a higher (improved) SGA score than one continuing to lose weight acutely.

B. Dietary Intake Changes

The patient's habitual dietary intake is categorized by duration and degree of deficit:

• Normal Habitual Diet: Adequate caloric and protein intake meeting KDOQI guidelines.
• Subnormal Solid Diet: Mild reduction in quantity or meal frequency (e.g., leaving 25–50% of food on the plate; missing 1 meal daily).
• Full Liquid Diet: Inability to tolerate solid foods, relying on oral nutrition supplement beverages or soups.
• Hypocaloric Clear Liquid: Markedly inadequate intake consisting of broths, tea, or water.
• Near-Complete Starvation / Fasting: Minimal to zero oral intake for multiple days.

C. Gastrointestinal Symptoms

Persistent gastrointestinal distress is a major driver of uremic anorexia and PEW. To receive diagnostic weight in the SGA, symptoms must occur almost daily for at least 2 consecutive weeks:

• Anorexia: Persistent loss of appetite, often accompanied by uremic dysgeusia (metallic taste) or meat aversion.
• Nausea: Constant or postprandial nausea interfering with intake.
• Vomiting: Frequency of emesis (occasional vs. daily post-dialysis emesis).
• Diarrhea: Chronic loose stools leading to nutrient malabsorption and electrolyte wasting.
• Early Satiety / Abdominal Fullness: Particularly prevalent in peritoneal dialysis patients due to increased intra-abdominal pressure from dialysate dwell volumes.

D. Functional Capacity / Energy Level

Functional status reflects the systemic impact of muscle wasting and chronic fatigue:

• Normal Functional Capacity: Ambulatory, fully independent in activities of daily living (ADLs), able to perform occupational work or vigorous exercise.
• Subnormal Work Performance: Ambulatory and independent in ADLs, but struggles with heavy exertion, stair climbing, or employment duties.
• Ambulatory with Limited ADLs: Difficulty with basic self-care, frequent resting, spending > 50% of waking hours seated.
• Wheelchair-Bound or Bedridden: Complete physical dependency, severe muscle weakness, inability to ambulate independently.

E. Metabolic Stress and Comorbid Illness

Catabolic stress accelerates somatic proteolysis. The clinician assesses the severity of underlying medical stressors:

• Low Stress: Stable maintenance dialysis, controlled hypertension, absence of acute infection.
• Moderate Stress: Controlled diabetes mellitus, congestive heart failure (NYHA Class II), chronic vascular access complications, mild localized decubitus ulcer.
• Severe Catabolic Stress: Active infectious peritonitis in PD, vascular access bacteremia/sepsis, active inflammatory bowel disease, systemic vasculitis, major surgery within 30 days, or non-healing diabetic gangrenous ulcers.

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2. Physical Examination Components

The physical examination objectively verifies the historical data by evaluating somatic fat and muscle stores alongside fluid volume:

Detailed Physical Examination Matrix

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3. The 7-Point Scoring Classification & Clinical Rubric

After synthesizing all historical domains and physical examination findings, the clinician assigns an aggregate clinical score from 1 to 7 based on holistic clinical judgment:

                               7-POINT SGA SPECTRUM
  [ 1 -------- 2 ]          [ 3 -------- 4 -------- 5 ]          [ 6 -------- 7 ]
Severely Malnourished    Mild to Moderately Malnourished         Well-Nourished

• Severe >10% weight loss • 5-10% weight loss; subnormal diet    • Stable dry weight
• Profound muscle hollows • Mild/moderate wasting at 1-2 sites  • Normal muscle/fat bulk
• Paper-thin fat pinch    • Reduced skinfold thickness          • High functional capacity
• Bedridden / severe GI   • Moderate functional impairment      • No persistent GI symptoms

Clinical Tiers and Scoring Definitions

1. Scores 6–7: Well-Nourished
   • Score 7: Patient demonstrates robust nutritional health. Stable dry weight (or intentional, healthy gain); no dietary restrictions beyond standard renal guidelines; zero persistent GI symptoms; high functional capacity; full, well-developed muscle bulk and normal subcutaneous fat cushions.
   • Score 6: Mostly well-nourished with very minor, vague symptoms (e.g., slight transient decrease in appetite over 1 week, or very subtle, questionable loss of upper-arm fat), but overall somatic stores, weight, and function remain entirely preserved.
2. Scores 3–5: Mild to Moderately Malnourished
   • Score 5: Mild nutritional decline. Minor weight loss (< 5% over 6 months); slight reduction in solid dietary intake; mild fatigue; minimal loss of subcutaneous fat or slight loosening of skin over the triceps, with well-preserved muscle mass.
   • Score 4: Definitive, unequivocal moderate malnutrition. Moderate weight loss (5% to 10% over 6 months); subnormal solid intake for several weeks; daily mild-to-moderate GI symptoms (nausea, early satiety); moderate muscle wasting (mild temporal hollowing, prominent clavicle) and obvious subcutaneous fat depletion; noticeable reduction in physical endurance.
   • Score 3: On the threshold of severe malnutrition. Weight loss approaching 10%; substantial dietary restriction; moderate-to-severe muscle wasting across multiple anatomical beds; ambulatory but struggling with basic household ADLs.
3. Scores 1–2: Severely Malnourished
   • Score 2: Advanced, profound nutritional depletion. Severe involuntary weight loss (> 10% over 6 months); persistent liquid diet or starvation; daily vomiting or intractable diarrhea; widespread muscle wasting (deep scooped temples, squared shoulders, visible ribs, interosseous depressions); severe fat loss (< 0.5 cm triceps pinch); marked functional impairment.
   • Score 1: Terminal, extreme cachexia. Total somatic muscle and fat exhaustion; completely bedridden; intractable uremic anorexia; skin tightly stretched across skeletal framework. Highest acute mortality risk.

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4. Prognostic Validity and Longitudinal Monitoring

Extensive multicenter validation studies, including data from the CANUSA study and the Dialysis Outcomes and Practice Patterns Study (DOPPS), have firmly established the prognostic power of the 7-point SGA:

• Mortality Prediction: In the CANUSA peritoneal dialysis cohort, each 1-point higher SGA score was associated with about a 25% lower relative risk of death; lower scores consistently predict higher mortality in HD and PD.
• Hospitalization Risk: Patients scoring in the malnourished range (SGA ≤ 5) have higher hospitalization rates and longer lengths of stay than well-nourished peers (scores 6–7).
• Longitudinal Tracking: Because the 7-point scale detects single-point increments, it is an ideal metric for quality assessment and performance improvement (QAPI) surveillance. KDOQI 2020 suggests nutrition screening at least biannually and a comprehensive assessment within the first 90 days of dialysis and annually (OPINION); in practice, many programs repeat the 7-point SGA about every 6 months in stable dialysis patients, and monthly in patients scoring ≤ 5 to monitor response to oral nutritional supplements (ONS), intradialytic parenteral nutrition (IDPN), or intraperitoneal amino acids (IPAA).