A 35-year-old man with fever, mucosal involvement, and >50% body surface area involvement with epidermal detachment is suspected to have Toxic Epidermal Necrolysis (TEN). Which investigation is most appropriate for assessing disease severity and guiding prognostic counselling?

## Investigation for Prognosis and Severity Assessment in TEN **Key Point:** The **TEN-4 score** (also called **SCORTEN** or **TEN-specific mortality risk score**) is the most validated and clinically useful investigation for assessing severity, predicting mortality, and guiding prognostic counselling in TEN. ### TEN-4 / SCORTEN Scoring System **High-Yield:** The TEN-4 score incorporates 4 readily available clinical and laboratory parameters: | Parameter | Score | | --- | --- | | **Age > 40 years** | +1 | | **Heart rate > 120 bpm** | +1 | | **Serum bicarbonate < 15 mEq/L** | +1 | | **Serum urea > 10 mmol/L (or BUN > 28 mg/dL)** | +1 | ### Mortality Risk Stratification **Clinical Pearl:** The TEN-4 score directly predicts in-hospital mortality: | TEN-4 Score | Mortality Risk | | --- | --- | | **0–1** | ~3–5% | | **2** | ~10–15% | | **3** | ~30–40% | | **≥4** | >60% | **Mnemonic:** **SCORTEN** — **S**core **C**alculated **O**n **R**ecognition of **T**EN for **E**arly **N**otification of **T**oxicity risk. ### Why TEN-4 is Superior for Prognosis 1. **Validated:** Prospectively validated in multiple cohorts; recommended by international dermatology guidelines 2. **Bedside applicable:** Uses only clinical signs and basic labs (no specialized testing needed) 3. **Early assessment:** Can be calculated within 24–48 hours of admission 4. **Guides management:** Helps identify high-risk patients needing ICU admission, aggressive supportive care, and specialist consultation 5. **Prognostic counselling:** Provides objective data for family discussions about mortality risk **Warning:** TEN-4 is calculated at **admission**, not during the acute phase. It predicts mortality **during hospitalization**, not long-term outcomes. ## Why Other Investigations Are Not Appropriate for Prognosis | Investigation | Issue | | --- | --- | | **Histopathology with apoptotic index** | While apoptotic index correlates with severity, it is not standardized, not readily available, and not used for prognostic scoring. Biopsy is for diagnosis, not prognosis. | | **Serum albumin and PT** | These reflect organ dysfunction but are not part of a validated prognostic score. Albumin is often low due to exudative losses, not baseline nutrition. | | **High-resolution CT chest** | Pulmonary involvement is a complication of TEN, not a predictor of mortality. CT is indicated only if respiratory symptoms develop; it does not guide initial prognostic counselling. |