What is the appropriate work‑up for a patient presenting with xerostomia (dry mouth)?

Work-Up for Dry Mouth (Xerostomia)

Initial Clinical Assessment

Begin by conducting a comprehensive medication review, as polypharmacy with anticholinergic drugs is the most common cause of xerostomia, particularly in elderly patients. 1, 2

Medication History

• Systematically review all medications for anticholinergic properties, including:
  • Antidepressants (especially tricyclics) 1, 2
  • Antihistamines and decongestants 1
  • Antimuscarinics and anxiolytics 1, 2
  • Antiparkinsonians 1, 2
  • Antipsychotics and pain medications 1
• Document use of diuretics, calcium channel blockers, lithium, and NSAIDs 1, 3
• Include over-the-counter products, as failing to review these is the most commonly missed diagnosis 3
• Assess alcohol and caffeine intake due to diuretic effects 1, 2

Focused Medical History

• Screen for systemic diseases commonly associated with xerostomia:
  • Diabetes mellitus (causes dry mouth through autonomic neuropathy and osmotic diuresis) 1, 3
  • Chronic kidney disease 1, 3
  • Thyroid dysfunction 1, 3
  • Sjögren's syndrome and other autoimmune disorders (rheumatoid arthritis, systemic lupus, scleroderma) 1, 3
• Inquire about dry eyes, as the combination suggests Sjögren's syndrome 1, 3
• Document history of head/neck radiation therapy 4, 5
• Assess for neurological symptoms (numbness, weakness, speech disturbance, gait abnormalities, memory loss) that may indicate underlying neurological disease 1, 3

Physical Examination

Oral Examination

• Assess for objective signs of reduced salivation (dry mucous membranes, lack of pooled saliva) 1, 2
• Examine for oral candidiasis, which is common with chronic xerostomia 2, 5
• Evaluate for dental caries and periodontal disease 2, 4
• Check for parotid gland enlargement (suggests Sjögren's syndrome) 3

General Examination

• Measure blood pressure, including orthostatic measurements 1, 3
• Assess for peripheral edema (indicates fluid retention) 1
• Perform neurological examination if gait disturbance or other neurological symptoms are present 1, 3

Laboratory Investigations

Order baseline blood tests to identify underlying endocrine or renal disease:

Essential Laboratory Tests

• Electrolytes and renal function (to detect chronic kidney disease) 1, 3
• HbA1c (to screen for diabetes mellitus) 1, 3
• Thyroid function tests (TSH, free T4) 1, 3
• Serum calcium and magnesium (hypocalcemia can cause multiple symptoms including fatigue and neurological manifestations) 3
• Urine dipstick with albumin:creatinine ratio (80% sensitive for proteinuria, indicates potential CKD) 1, 3

Autoimmune Screening (When Indicated)

Consider autoimmune testing when:

• Dry mouth is accompanied by dry eyes 1, 3
• Systemic symptoms are present 3
• No clear medication or metabolic cause is identified 3

Specific tests for Sjögren's syndrome include:

• Anti-SSA/Ro and anti-SSB/La antibodies 1
• Antinuclear antibodies (ANA) 1
• Rheumatoid factor 1

Objective Salivary Gland Function Assessment

Measure whole salivary flow rates before initiating therapeutic interventions, as subjective feelings of dryness often do not match objective glandular function. 1

Salivary Flow Rate Measurement

• Calculate salivary flow rate (SFR) using the formula: total salivary volume collected ÷ time taken (mL/min) 1
• Xerostomia is defined as SFR <0.1 mL/min 1
• Record the time taken for saliva collection to allow accurate calculation 1
• Consider salivary scintigraphy for additional functional assessment 1

Additional Diagnostic Considerations

Rule Out Non-Xerostomia Conditions

• Exclude oral candidiasis 1
• Exclude burning mouth syndrome 1
• Assess for dysphagia, which may increase saliva pooling due to reduced clearance (common in neurological disorders) 1

Sleep Disorder Screening

• Evaluate for sleep disorders, as they contribute to nocturnal dry mouth and daytime fatigue 3
• Screen for obstructive sleep apnea if indicated 1

Common Pitfalls to Avoid

• Do not dismiss dry mouth as trivial, as it may signal serious autoimmune disease 3
• Do not overlook sleep disorders as contributors to symptoms 3
• Do not assume peripheral vestibular causes without considering posterior circulation stroke if gait abnormalities are present 3
• Do not fail to measure orthostatic blood pressure when medications or autonomic dysfunction may explain symptoms 3

Specialist Referral Indications

Rheumatology Referral

• Refer when clinical features suggest Sjögren's syndrome: persistent dry eyes, parotid gland enlargement, positive autoimmune markers 2, 3

Dental Referral

• Immediate referral for: complicated oral infections, severe dental caries, or advanced periodontal disease 2

Other Specialist Referrals

• Speech-language pathology for dysphagia assessment 2
• Palliative care consultation for refractory xerostomia despite comprehensive management 2
• Neurology if neurological symptoms suggest underlying disease 1, 3