In an 82-year-old man with six-month intermittent diarrhea and oropharyngeal dysphagia, what blood and stool investigations should be performed?

Investigations for 82-Year-Old Male with Intermittent Diarrhea and Oropharyngeal Dysphagia

In this 82-year-old man with 6 months of intermittent diarrhea, you should obtain: (1) Blood tests: complete blood count, ferritin, tissue transglutaminase IgA (with total IgA or alternative testing if deficient), and thyroid function tests; (2) Stool tests: fecal calprotectin, Giardia testing, and Clostridium difficile testing (combined GDH/PCR plus toxin EIA). 1

Blood Investigations

The British Society of Gastroenterology 2018 guidelines provide the strongest framework for initial screening 1:

• Complete blood count and ferritin: Essential to detect anemia and iron deficiency, which may indicate malabsorption or inflammatory bowel disease. In elderly patients, micronutrient deficiencies from malabsorption often present covertly and can be devastating given reduced nutritional reserve 2.

• Tissue transglutaminase IgA (tTG-IgA) with total IgA level: Celiac disease screening has high sensitivity and specificity and is strongly recommended 1. Critical caveat: If IgA deficient, you must use IgG-based testing (IgG EMA or IgG tTG) to avoid false negatives 1.

• Thyroid function tests: Hyperthyroidism is a recognized cause of chronic diarrhea in elderly patients and should be excluded 1.

Do NOT routinely order ESR or CRP for IBD screening—the AGA guidelines specifically recommend against this approach 3.

Stool Investigations

Primary Stool Tests

• Fecal calprotectin: This inflammatory marker is strongly recommended by both British and American guidelines 3, 1. It effectively distinguishes inflammatory bowel disease from functional disorders. Use 50 μg/g as the threshold—levels above this make IBD more likely and warrant further investigation.

• Giardia testing: The AGA guidelines support testing for Giardia in chronic diarrhea 3. Stool ELISA has 92% sensitivity and 98% specificity, superior to traditional ova and parasite examination 1. This is particularly important in elderly patients where protozoan infections can cause chronic symptoms.

• Clostridium difficile testing: Use the two-stage approach recommended by European consensus 1:

  • First: Glutamate dehydrogenase EIA or PCR to detect organism presence
  • Second: Toxin EIA to confirm active toxin production

  Important pitfall: Do not treat based on PCR alone without toxin confirmation, as post-infectious IBS after C. difficile is recognized and excessive antibiotics should be avoided 1.

Additional Stool Testing Considerations

• Three fresh stool samples for ova, cysts, and parasites: While sensitivity is only 60-90%, this remains valuable if Giardia ELISA is unavailable or if other parasitic infections are suspected 1.

Special Considerations for This Patient

The Oropharyngeal Dysphagia Component

While the dysphagia itself requires separate evaluation (videofluoroscopy is the gold standard 4), its presence raises two critical concerns:

1. Malnutrition risk: Up to 55% of elderly patients with dysphagia are at risk of malnutrition 4. This makes the ferritin and CBC even more important to detect nutritional deficiencies.

2. Systemic disease consideration: The combination of diarrhea and dysphagia could suggest systemic conditions like systemic sclerosis, which can cause both gastrointestinal dysmotility and malabsorption 1. Consider this in your differential diagnosis.

Age-Specific Concerns

In an 82-year-old, consider:

• Microscopic colitis: A secretory diarrhea affecting older persons that may not be detected by calprotectin alone 5
• Chronic pancreatic insufficiency: Can occur without anatomic abnormality in elderly patients 2
• Bacterial overgrowth: More common in elderly and can occur without anatomic small bowel abnormality 2

What NOT to Order Initially

• Serologic tests for IBS-D diagnosis: The AGA makes no recommendation for currently available tests (anti-CdtB, anti-vinculin) due to low sensitivity (20-40%) despite high specificity 3
• ESR or CRP: Not recommended for IBD screening 3
• Stool weights: No longer recommended due to limited clinical value 1

Clinical Algorithm

1. Order blood tests (CBC, ferritin, tTG-IgA with total IgA, TSH) and stool tests (calprotectin, Giardia ELISA, C. difficile two-stage testing) simultaneously
2. If tTG-IgA positive or IgA deficient with positive IgG testing → proceed to endoscopy for celiac confirmation
3. If calprotectin elevated (>50 μg/g) → consider colonoscopy for IBD evaluation
4. If initial tests negative but symptoms persist → consider bile acid diarrhea testing and further evaluation for malabsorption or bacterial overgrowth