What labs are recommended for a peptic ulcer workup?

Laboratory Testing for Peptic Ulcer Workup

All patients with suspected peptic ulcer disease should undergo Helicobacter pylori testing, and those presenting with acute complications require routine laboratory studies including complete blood count, metabolic panel, and arterial blood gas analysis to assess disease severity and guide resuscitation. 1, 2

Essential Laboratory Tests

For Acute/Complicated Presentations

Obtain these labs immediately for patients with suspected perforated or bleeding peptic ulcer:

• Complete blood count (CBC) to detect anemia from bleeding or leukocytosis from perforation 2
• Comprehensive metabolic panel to identify metabolic acidosis and electrolyte derangements 2
• Arterial blood gas analysis to assess acid-base status and severity of physiologic derangement 2
• Serum amylase may be elevated in perforation, though this finding is non-specific 2

Important caveat: These laboratory findings help assess complications and guide resuscitation but do not confirm the diagnosis of peptic ulcer itself—they only detect associated complications. 2

For All Peptic Ulcer Patients: H. pylori Testing

H. pylori testing is mandatory in all patients with peptic ulcer disease, whether bleeding, perforated, or uncomplicated. 1, 2 This is critical because eradication reduces rebleeding rates from 26% to near zero in H. pylori-associated ulcers. 1, 3

H. pylori Testing Options

Non-Invasive Tests (Preferred for Active Infection Detection)

Urea breath test (UBT):

• Sensitivity: 88-95% 1, 2
• Specificity: 95-100% 1, 2
• Best choice for bleeding peptic ulcers 4

Stool antigen test:

• Sensitivity: 94% 1, 2
• Specificity: 92% 1, 2
• Acceptable alternative to UBT 1, 2

Invasive Tests (During Endoscopy)

Endoscopic tissue biopsy for histology, rapid urease test (CLO test), or culture 1, 2

Critical limitation in bleeding ulcers: Histologic study and CLO test have significantly reduced sensitivity at initial endoscopy due to intragastric blood and altered bacterial load—first-day sensitivity drops to 67-75%. 4 UBT maintains 100% sensitivity even in acute bleeding. 4

Serology

Not recommended for treatment decisions because it cannot distinguish active from past infection and cannot confirm eradication. 2 However, it has 100% sensitivity for detecting exposure. 4

Testing Protocol

Stop these medications at least 2 weeks before testing to avoid false-negative results:

• Proton pump inhibitors (PPIs) 2
• Antibiotics 2
• Bismuth products 2

This is the most common cause of false-negative H. pylori tests. 2

Diagnostic Algorithm

For suspected perforated peptic ulcer:

1. Obtain CBC, metabolic panel, and arterial blood gas immediately 2
2. Perform CT scan as preferred imaging modality 2
3. Test for H. pylori once patient is stabilized 2

For bleeding peptic ulcer:

1. Obtain routine labs to assess hemodynamic status 2
2. Perform urgent endoscopy with gastric biopsies for H. pylori testing 3
3. If endoscopic biopsy not obtained, use UBT or stool antigen test for non-invasive confirmation 3
4. UBT is superior to histology and CLO test in acute bleeding 4

For uncomplicated peptic ulcer:

1. Use non-invasive H. pylori testing (UBT or stool antigen) in patients under 55 years without alarm symptoms 5
2. Perform upper endoscopy in patients over 55 years or with alarm symptoms to rule out malignancy 5

Post-Treatment Confirmation

Confirm H. pylori eradication at least 4 weeks after completing therapy using UBT or stool antigen test—these are the only tests that can confirm cure. 3, 5 Serology cannot be used for this purpose. 5