A 42-year-old woman is admitted with sepsis secondary to pneumonia. Her qSOFA score is 2 (respiratory rate 28, altered mental status). Regarding sepsis definitions, diagnostic criteria, and risk stratification, all of the following are correct EXCEPT:

Explanation

## Sepsis Definitions and Diagnostic Criteria: Sepsis-3 Framework ### Correct Answer: Procalcitonin Is NOT Diagnostic **Key Point:** Procalcitonin is a **biomarker**, not a diagnostic criterion for sepsis. Sepsis-3 (2016) defines sepsis based on clinical criteria (SOFA score ≥2 from baseline) plus suspected infection — not on any single laboratory value. **High-Yield:** Procalcitonin has high sensitivity but moderate specificity for bacterial infection. It can be elevated in non-infectious conditions (trauma, surgery, pancreatitis) and is NOT required for sepsis diagnosis. ### Sepsis-3 Definitions | Condition | Definition | Key Features | |-----------|-----------|---------------| | **Infection** | Suspected or confirmed pathogenic invasion of normally sterile tissue | Clinical suspicion + cultures/imaging | | **Sepsis** | Infection + SOFA ≥2 (from baseline) | No organ dysfunction = not sepsis | | **Severe Sepsis** | Sepsis + organ dysfunction | Obsolete term (replaced by sepsis in Sepsis-3) | | **Septic Shock** | Sepsis + vasopressor requirement (MAP ≥65) + lactate >2 mmol/L | Highest mortality tier | ### Why the Other Options Are Correct **Option 1 — qSOFA Specificity:** qSOFA (quick SOFA) score ≥2 has **high specificity** (~90%) for identifying patients at risk of poor outcomes, ICU admission, and mortality. It is more specific but less sensitive than SIRS [cite:Sepsis-3 2016]. **Option 2 — SIRS vs. qSOFA:** SIRS criteria (fever, HR >90, RR >20, WBC >12,000 or <4,000) are **highly sensitive** but **poorly specific** for sepsis; many non-infectious conditions trigger SIRS. qSOFA is more specific but misses some cases. **Option 3 — SOFA ≥2 Defines Sepsis:** Sepsis-3 explicitly defines sepsis as infection + SOFA score ≥2 from baseline. This is the gold standard diagnostic criterion [cite:Sepsis-3 2016]. **Clinical Pearl:** Remember the **Sepsis-3 hierarchy**: Infection alone → add SOFA ≥2 → now it's sepsis. Add vasopressor need + lactate → septic shock. **Mnemonic:** **SOFA** = **S**equential **O**rgan **F**ailure **A**ssessment. Score ≥2 from baseline = sepsis (if infection present). ### Role of Procalcitonin in Sepsis ProCalcitonin is useful for: - **Antibiotic de-escalation:** PCT-guided protocols reduce antibiotic duration without worsening outcomes. - **Prognostic stratification:** Higher levels correlate with severity and mortality. - **NOT diagnostic:** Cannot diagnose or exclude sepsis alone; must be used with clinical judgment.