Are there any at-home screening tests for Cushing's syndrome?

At-Home Screening Tests for Cushing's Syndrome

Yes, late-night salivary cortisol is an effective at-home screening test for Cushing's syndrome that you can recommend to patients, with a sensitivity of 95% and specificity of 100%. 1

Primary At-Home Test: Late-Night Salivary Cortisol

Late-night salivary cortisol (LNSC) is the most practical at-home screening option because it:

• Can be collected by the patient at home around 11 PM (2300 hours) using a simple commercial collection device 2
• Measures free (active) cortisol that equilibrates with plasma levels 2
• Demonstrates excellent diagnostic accuracy with 92-95% sensitivity and 100% specificity 1, 2
• Requires 2-3 samples to account for variability and improve reliability 3
• Remains safe for laboratory personnel even during infectious disease concerns like COVID-19 when proper precautions are used 3

The test works by detecting loss of normal cortisol circadian rhythm—healthy individuals have very low cortisol at night (nadir around 1.2 nmol/L), while patients with Cushing's syndrome maintain elevated levels (around 24.0 nmol/L) 2.

Secondary At-Home Option: 24-Hour Urine Free Cortisol (UFC)

While technically "at-home," this test is more cumbersome:

• Requires collecting all urine over 24 hours for 2-3 consecutive days 3
• Has 89-95% sensitivity and 98-100% specificity 1, 4
• More difficult for patient compliance compared to salivary testing 5
• Should not be used in patients with kidney disease (creatinine clearance <60 mL/min) or significant polyuria (>5 L/24 hours) 3

The combination of an elevated LNSC and/or elevated UFC identifies 100% of patients with proven Cushing's syndrome 2, making these complementary tests when used together.

What Cannot Be Done at Home

The dexamethasone suppression test (DST) requires:

• Taking dexamethasone medication at specific times
• Blood draw the following morning at a medical facility 3
• This is NOT a true at-home test despite the medication being taken at home

Clinical Context for Ordering

Recommend screening only when clinical suspicion is appropriate:

• In children: Screen only if unexplained weight gain occurs WITH either decreased height velocity or declining height percentile—this combination has high sensitivity and specificity 3
• In adults: Screen when multiple specific features are present, including facial plethora, proximal muscle weakness, wide purple striae (>1 cm), or easy bruising 6, 4

Important Caveats

• False positives can occur with severe obesity, uncontrolled diabetes, depression, alcoholism, and pregnancy 5
• Morning salivary cortisol is NOT useful—it shows too much overlap between normal and Cushing's patients 2
• Random cortisol measurements are unreliable and should never be used for screening 6
• If initial screening is abnormal, repeat 1-2 tests to confirm before pursuing further workup 5, 1

For patients with intermediate-to-high clinical suspicion, starting with multiple LNSC samples (2-3 collections) provides the easiest and most reliable at-home screening approach 3, 5, with UFC collection as a reasonable alternative or complementary test 5, 1.