A 28-year-old female from endemic region presents with abdominal pain, diarrhea, and eosinophilia (WBC 12,000/μL, eosinophils 18%). Stool examination reveals barrel-shaped eggs with mucoid plugs. What is the most appropriate investigation to confirm the diagnosis and assess severity?

## Investigation of Choice for Trichuris trichiura Confirmation and Severity Assessment **Key Point:** Quantitative stool examination on multiple consecutive days is the gold standard for confirming *Trichuris trichiura* (whipworm) infection and assessing parasite burden, which correlates directly with clinical severity and treatment response. ### Why Quantitative Stool Examination is Optimal 1. **Diagnostic confirmation**: Barrel-shaped eggs with polar mucoid plugs are pathognomonic for *Trichuris trichiura*; direct visualization confirms diagnosis. 2. **Severity assessment**: Egg count (eggs per gram of feces, EPG) correlates with: - Clinical symptoms (light infection: <1,000 EPG; moderate: 1,000–10,000 EPG; heavy: >10,000 EPG) - Risk of complications (dysentery, rectal prolapse, anemia) - Treatment efficacy (post-therapy egg reduction rate) 3. **Multiple samples**: Trichuris eggs are shed intermittently; 3 consecutive stool samples increase diagnostic sensitivity from ~60% (single sample) to >95%. ### Diagnostic Features of *Trichuris trichiura* | Feature | Finding | Significance | |---|---|---| | **Egg morphology** | Barrel-shaped, 50–55 μm, polar mucoid plugs | Pathognomonic | | **Stool examination** | Quantitative EPG | Correlates with severity | | **Eosinophilia** | Mild (10–20%) | Reflects Th2 response | | **Clinical presentation** | Dysentery, tenesmus, rectal prolapse (heavy infection) | Depends on worm burden | | **Serology** | IgG positive but non-specific | Cannot differentiate active from past infection | **High-Yield:** The **Kato-Katz thick smear** or **formalin-ether concentration** methods are preferred for quantitative stool examination in helminth infections, as they allow accurate EPG calculation and severity grading. **Clinical Pearl:** In heavy *Trichuris* infections (>10,000 EPG), rectal prolapse and iron-deficiency anemia are common; quantitative egg count helps predict these complications and guides intensity of treatment (single-dose vs. prolonged therapy). ### Mnemonic: **STOOL-QUANT** - **S**tool examination → gold standard - **T**richuris eggs → barrel-shaped, mucoid plugs - **O**n 3 consecutive days → increases sensitivity - **O**f feces → quantitative EPG - **L**ight/moderate/heavy → correlates with severity - **Q**uantitation → guides treatment intensity - **U**nderstanding burden → predicts complications - **A**ssesses response → post-treatment EPG reduction - **N**on-invasive → preferred method - **T**herapy monitoring → essential for follow-up ### Why Other Investigations Are Suboptimal **Serology (IgG):** Positive in both active and past infections; cannot differentiate or quantify current parasite burden. **Colonoscopy:** Invasive, unnecessary for diagnosis; reserved for complications (e.g., rectal prolapse, severe dysentery unresponsive to anthelmintics). **Ultrasound:** Non-specific; may show hepatomegaly or ascites in advanced disease but does not confirm diagnosis or assess parasite burden.