What Does Defervesce Mean?
Defervesce means the resolution or disappearance of fever—specifically, when a patient's elevated body temperature returns to normal range (typically below 38.0°C). 1
Clinical Context and Timeline
Defervescence is a key clinical marker used to assess response to antimicrobial therapy and typically occurs over a predictable timeframe depending on patient risk factors and infection severity. 1
Expected Time to Defervescence
- Low-risk patients (e.g., otherwise healthy individuals with uncomplicated infections) typically defervesce within 2 days of appropriate antibiotic therapy 1
- High-risk patients (e.g., neutropenic patients, those with severe infections, bacteremia, or multiple comorbidities) have a median time to defervescence of 5-7 days 1
- In febrile neutropenic cancer patients receiving appropriate antibiotic regimens, the median time to defervescence ranges from 2-7 days, with a median of 5 days 1
Factors That Delay Defervescence
Several patient and disease characteristics are associated with slower defervescence, even with appropriate therapy: 1
- Advanced age (>65 years) 1
- Multiple coexisting illnesses 1
- Alcoholism 1
- Multilobar pneumonia 1
- Bacteremia 1
- COPD or other chronic lung disease 1
- Increasing severity of initial presentation 1
Clinical Significance
The pattern and timing of defervescence helps clinicians determine whether to continue, modify, or escalate antimicrobial therapy. 1
- Persistent fever for 3-5 days does not automatically indicate treatment failure if the patient is otherwise clinically stable and improving 1, 2
- Clinicians should typically wait at least 3-5 days before making changes to an antimicrobial regimen based solely on persistent fever, unless clinical deterioration occurs 1
- Fever that persists beyond 3-5 days warrants reassessment including review of cultures, physical examination, imaging, and consideration of non-bacterial causes (fungal infection, drug fever, abscess, catheter infection) 1
Important Caveats
Defervescence patterns vary significantly by pathogen: 1
- Streptococcus pneumoniae infections typically defervesce most rapidly (2-4 days in healthy adults) 1
- Mycoplasma pneumoniae and Chlamydophila pneumoniae may require 10-14 days of therapy before defervescence 1
- Legionella infections show slower defervescence compared to pneumococcal disease 1
The degree of defervescence after antipyretic administration (e.g., acetaminophen) is age-dependent and does NOT distinguish between bacterial and non-bacterial infections, making it unreliable for diagnostic purposes 3