What labs should be ordered for a patient presenting with nausea, vomiting, and epigastric pain?

Laboratory Evaluation for Nausea, Vomiting, and Epigastric Pain

For patients presenting with nausea, vomiting, and epigastric pain, a comprehensive laboratory panel should include complete blood count (CBC), comprehensive metabolic panel (CMP), lipase, and amylase as first-line tests to evaluate the most common and serious etiologies. 1

First-Line Laboratory Tests

• Complete Blood Count (CBC)

  • Evaluates for leukocytosis suggesting infection or inflammation
  • Assesses for anemia which may indicate GI bleeding
  • Helps determine severity of inflammatory conditions

• Comprehensive Metabolic Panel (CMP)

  • Liver function tests (AST, ALT, bilirubin, alkaline phosphatase)
    • Abnormal in 15-30% of various GI conditions 2
    • Essential for evaluating hepatobiliary causes of epigastric pain
  • Electrolytes and renal function
    • Identifies dehydration from vomiting
    • Detects acid-base disturbances
  • Glucose level
    • May be elevated in pancreatitis

• Lipase

  • Most specific test for acute pancreatitis
  • Elevation >3 times upper limit of normal has 100% sensitivity and 99% specificity for acute pancreatitis 1
  • Remains elevated longer than amylase (valuable if presentation is delayed) 3

• Amylase

  • Complementary to lipase for diagnosing pancreatitis
  • Less specific than lipase but technically simple and widely available 3
  • Note: Both enzymes may be normal in certain cases of pancreatitis (e.g., hyperlipidemic pancreatitis) 4

Second-Line Laboratory Tests (Based on Clinical Suspicion)

• Lipid Panel

  • Essential if hypertriglyceridemia-induced pancreatitis is suspected
  • Severe hypertriglyceridemia (>1000 mg/dL) can cause pancreatitis with normal amylase/lipase 4

• C-Reactive Protein (CRP)

  • Best available laboratory marker for severity assessment in pancreatitis
  • Peak CRP >210 mg/L in first four days or >150 mg/L at 48 hours indicates severe disease 1

• Pregnancy Test

  • For women of childbearing age to rule out hyperemesis gravidarum or ectopic pregnancy

• Helicobacter pylori Testing

  • Consider if peptic ulcer disease is suspected

• COVID-19 Testing

  • In appropriate epidemiological settings, as GI symptoms may precede respiratory symptoms 2

Diagnostic Algorithm

1. Initial Evaluation: CBC, CMP, lipase, amylase

   • If lipase >3x upper limit: Diagnose acute pancreatitis and proceed with appropriate imaging
   • If liver enzymes elevated: Consider hepatobiliary causes and appropriate imaging
   • If both normal: Proceed to second-line testing based on clinical suspicion

2. Second-Line Testing (based on clinical findings and initial results):

   • Persistent symptoms with normal initial labs: Consider H. pylori testing, lipid panel
   • Signs of infection: Blood cultures, COVID-19 testing if appropriate
   • Severe or concerning presentation: Add CRP for prognostication

Important Clinical Considerations

• Epigastric pain can have multiple serious etiologies including myocardial infarction, pancreatitis, and acute aortic syndromes that require prompt diagnosis 2

• Laboratory tests should be interpreted in conjunction with the timing and nature of pain, relationship to meals, and associated symptoms 2

• Normal amylase and lipase do not completely exclude pancreatitis, particularly in cases of hyperlipidemia or chronic pancreatitis 4

• Consider atypical presentations of pancreatitis which may present with minimal abdominal symptoms but significant systemic manifestations 5

• In patients with abnormal liver enzymes, approximately 15% of COVID-19 patients may have elevated AST/ALT, which should be considered during periods of high prevalence 2

By following this structured laboratory evaluation approach, clinicians can efficiently diagnose the cause of nausea, vomiting, and epigastric pain while minimizing unnecessary testing and delays in treatment.