What labs should be ordered for a patient presenting with oral ulcers and xerostomia (dry mouth)?

Laboratory Workup for Oral Ulcers and Xerostomia

For patients presenting with oral ulcers and dry mouth, order a first-line panel including complete blood count, fasting blood glucose, HIV antibody, and syphilis serology, as these tests screen for critical underlying conditions including hematologic malignancies, immunosuppression, and infections that directly impact morbidity and mortality. 1, 2

Essential First-Line Laboratory Tests

The following blood tests should be obtained before considering biopsy and serve dual purposes of excluding contraindications to biopsy while identifying systemic diseases 1:

• Complete blood count (CBC) - Rules out blood system diseases such as anemia, leukemia, and neutropenia that can present with oral ulceration 1, 2
• Fasting blood glucose - Identifies diabetes, which is a susceptible factor for invasive fungal infections and can cause xerostomia 1, 3
• HIV antibody testing - Excludes HIV infection, which has 35% prevalence of oral candidiasis and increases risk of opportunistic oral infections 1, 3
• Syphilis serology - Rules out syphilitic ulcers 1, 2
• Blood coagulation studies - Excludes surgical contraindications if biopsy becomes necessary 1

Additional Testing Based on Clinical Suspicion

For Recurrent or Multiple Ulcers

When ulcers are recurrent or multiple, expand the workup to include 4:

• Nutritional deficiency screening: Iron, folate, and vitamin B12 levels (recurrent aphthous stomatitis shows OR 3.75 for B12 deficiency, OR 7.55 for folate deficiency, and OR 2.62 for ferritin deficiency) 3
• Autoimmune markers if systemic autoimmune disease is suspected based on history of joint pain, fatigue, or other systemic symptoms 1, 4

For Suspected Bullous Diseases

If the clinical presentation suggests pemphigus, pemphigoid, or lichen planus (sloughing tissue, blistering, erythema) 1, 2:

• Serum specific antibodies: Dsg1, Dsg3, BP180, and BP230 should be obtained before biopsy 1, 4
• Direct immunofluorescence (DIF) on biopsy specimens is diagnostic for pemphigus vulgaris (positive for IgG and C3 deposition) 1, 2

For Xerostomia-Specific Evaluation

When dry mouth is prominent 1:

• Consider Sjögren syndrome workup if patient has concurrent dry eyes, joint pain, or fatigue (includes anti-SSA/Ro, anti-SSB/La antibodies) 1, 5
• Review medication list thoroughly, as polypharmacy (>3 medications) has OR 2.9 for dry mouth 3, 5

Critical Timing Considerations

Do not delay biopsy beyond 2 weeks for persistent ulcers, as malignancy and serious systemic diseases must be excluded 2, 4. The laboratory workup should be obtained concurrently with clinical evaluation, not sequentially, to avoid diagnostic delays 1.

Common Pitfalls to Avoid

• Overlooking systemic associations: Multiple oral ulcers may indicate Crohn's disease, blood disorders, or autoimmune conditions that require additional gastroenterology or rheumatology evaluation 2, 4
• Inadequate initial workup: Relying solely on clinical appearance without appropriate laboratory testing for persistent ulcers leads to delayed diagnosis 4
• Missing medication-induced causes: Antihistamines, diuretics, antidepressants, and anticholinergic medications commonly cause xerostomia 1, 5
• Failing to test for nutritional deficiencies: These are highly prevalent in recurrent aphthous stomatitis and are easily correctable 3

When to Refer

Refer to oral medicine specialist if 4:

• Ulcers persist beyond 2 weeks despite initial treatment
• Laboratory abnormalities suggest hematologic malignancy (abnormal CBC requiring bone marrow biopsy and immunotyping) 1
• Suspected autoimmune bullous disease requiring specialized biopsy techniques with DIF 2, 4