Should dehydration be assessed in an older adult patient with skin tags, particularly those with a history of medical conditions such as diabetes or kidney disease?

Skin Turgor Testing Should NOT Be Used to Assess Dehydration in Older Adults

Do not use skin turgor (the "skin tag check") or any other simple clinical signs to assess dehydration in older adults—these methods are unreliable and should be replaced with serum osmolality measurement. 1

Why Clinical Signs Fail in Older Adults

The ESPEN guidelines explicitly state with Grade A recommendation (83-100% consensus) that simple signs and tests commonly used to assess dehydration—including skin turgor, mouth dryness, weight change, urine color, and urine specific gravity—shall NOT be used to assess hydration status in older adults. 1

Evidence Against Clinical Assessment

• A Cochrane systematic review pooled diagnostic data from multiple studies comparing clinical signs against the gold standard (serum osmolality) and found that none were consistently useful in indicating hydration status in older adults. 1

• These signs have either not been shown to be usefully diagnostic or have been definitively shown to lack diagnostic accuracy. 1

• More recent diagnostic accuracy studies in older adults have confirmed these findings. 1

• Clinical judgment alone is highly fallible in older adults for assessing hydration status. 1

The Correct Approach: Laboratory Testing

Directly measured serum or plasma osmolality is the primary and most reliable indicator of hydration status in older adults. 1, 2, 3

Recommended Diagnostic Algorithm

• First-line test: Directly measured serum or plasma osmolality with an action threshold of >300 mOsm/kg indicating low-intake dehydration requiring immediate intervention. 1, 3

• Alternative when direct measurement unavailable: Use the calculated osmolarity equation: osmolarity = 1.86 × (Na+ + K+) + 1.15 × glucose + urea + 14 (all measured in mmol/L) with an action threshold of >295 mmol/L. 1, 3

• This recommendation has Grade B evidence with 94% expert consensus from ESPEN. 1

Why Serum Osmolality Is the Gold Standard

• When fluid intake is inadequate, the fluid within and around cells becomes more concentrated, raising serum and plasma osmolality—this is the key physiological trigger of protective mechanisms. 1

• The US Panel on Dietary Reference Intakes for Electrolytes and Water explicitly states: "The primary indicator of hydration status is plasma or serum osmolality." 1

• This standard is based on decades of agreed-upon physiology and biochemistry among hydration experts. 1

• In older adults, renal function is often poor, so renal parameters no longer accurately signal low-intake dehydration, making osmolality even more critical. 1, 2

Clinical Significance in Older Adults

Dehydration carries serious consequences that make accurate diagnosis essential:

• Older adults with raised serum osmolality (>300 mOsm/kg) have increased risk of mortality. 1, 2

• One high-quality cohort study showed an associated doubling in risk of 4-year disability. 1, 2

• Low-intake dehydration is particularly common in frail, vulnerable older adults living in residential care or admitted to hospital. 1, 2

When to Screen

All older persons should be screened for low-intake dehydration in the following situations: 1, 3

• When they contact the healthcare system
• If clinical condition changes unexpectedly
• Periodically when malnourished or at risk of malnutrition
• During acute deterioration of health or poor food intake

Special Considerations for High-Risk Patients

Older adults with diabetes or kidney disease warrant particular attention:

• These patients are at increased risk due to their underlying conditions affecting fluid balance. 2

• Diabetes can cause osmotic diuresis leading to fluid losses. 1

• Impaired renal function reduces the kidney's ability to concentrate urine and conserve water. 1, 2

• However, the diagnostic approach remains the same: use serum osmolality, not clinical signs. 1, 2, 3

Critical Pitfalls to Avoid

• Never rely on skin turgor or other physical examination findings alone without laboratory confirmation, especially in older adults where signs are subtle and unreliable. 1, 3

• Do not use bioelectrical impedance—it has not been shown to be usefully diagnostic (100% consensus against use). 1, 3

• Ensure glucose and urea are within normal ranges when interpreting osmolality, as abnormalities in these independently elevate values. 3

• Failing to recognize dehydration due to absence of typical clinical signs can lead to delayed treatment and worse outcomes. 2, 3