Fever In The Immune Compromised Host and Recurrent Fever

Introduction

Understanding fever in immunocompromised patients and recurrent fever patterns is crucial for success in the MCCQE1 exam and for practicing medicine in Canada. This comprehensive guide will help you prepare for the Canadian medical licensing exam by covering key concepts, Canadian guidelines, and providing practice questions.

Fever in the Immunocompromised Host

Definition and Importance

Fever in an immunocompromised patient is defined as:

A single oral temperature of >38.3°C (101°F) or a temperature of >38.0°C (100.4°F) sustained for >1 hour.

This definition is crucial for MCCQE1 preparation, as it differs from fever definitions in immunocompetent patients.

Common Causes of Immunocompromise in Canada

Approach to Fever in Immunocompromised Patients

Recurrent Fever

Definition

Recurrent fever is characterized by:

Repeated episodes of fever separated by periods of normal body temperature and apparent good health.

Common Patterns of Recurrent Fever

1. Periodic Fever: Regular intervals between fever episodes
2. Cyclic Fever: Predictable cycle of fever and symptom-free periods
3. Relapsing Fever: Fever episodes with varying intervals

Differential Diagnosis of Recurrent Fever in Canada

Diagnostic Approach to Recurrent Fever

1. Detailed history, including:
   • Travel history
   • Family history
   • Ethnic background (relevant for genetic disorders)
2. Physical examination during and between fever episodes
3. Laboratory investigations:
   • Complete blood count with differential
   • Inflammatory markers (ESR, CRP)
   • Blood cultures
   • Serological tests for suspected pathogens
4. Imaging studies as indicated
5. Genetic testing for suspected hereditary periodic fever syndromes

Canadian Guidelines for Managing Fever in Immunocompromised Patients

The Association of Medical Microbiology and Infectious Disease (AMMI) Canada provides guidelines for managing febrile neutropenia, which are crucial for MCCQE1 preparation:

1. Empiric antibiotic therapy should be initiated within 60 minutes of presentation
2. Initial empiric therapy should include an anti-pseudomonal β-lactam antibiotic
3. Vancomycin should not be used routinely but may be added for specific indications
4. Antifungal therapy should be considered in high-risk patients with persistent fever
5. G-CSF is not routinely recommended but may be considered in specific high-risk patients

Key Points to Remember for MCCQE1

• Define fever in immunocompromised patients as >38.3°C once or >38.0°C for >1 hour
• Recognize common causes of immunocompromise in the Canadian context
• Understand the step-wise approach to managing fever in immunocompromised patients
• Differentiate between periodic, cyclic, and relapsing fever patterns
• Be familiar with both infectious and non-infectious causes of recurrent fever relevant to Canada
• Know the AMMI Canada guidelines for managing febrile neutropenia
• Understand the importance of prompt empiric antibiotic therapy in immunocompromised patients with fever

Sample Question

# Sample Question

A 45-year-old woman presents to the emergency department with a temperature of 38.5°C. She underwent allogeneic stem cell transplantation for acute myeloid leukemia 3 months ago and is on immunosuppressive therapy. She reports feeling generally unwell for the past 24 hours but denies any localizing symptoms. Her vital signs are: blood pressure 110/70 mmHg, heart rate 110 bpm, respiratory rate 20 breaths/min, and oxygen saturation 98% on room air. Physical examination is unremarkable except for mild tachycardia. Which one of the following is the most appropriate next step in management?

- [ ] A. Obtain blood cultures and observe for 24 hours
- [ ] B. Start oral ciprofloxacin and follow up in 48 hours
- [ ] C. Admit for observation and serial blood tests
- [ ] D. Obtain blood cultures and start intravenous broad-spectrum antibiotics
- [ ] E. Perform chest X-ray and urinalysis before deciding on treatment

Explanation

The correct answer is:

• D. Obtain blood cultures and start intravenous broad-spectrum antibiotics

This patient is presenting with fever in the setting of recent stem cell transplantation and ongoing immunosuppressive therapy, which classifies her as an immunocompromised host. In such patients, fever is a medical emergency due to the high risk of severe infections and sepsis.

According to Canadian guidelines (AMMI Canada):

1. Fever in immunocompromised patients should be treated promptly and aggressively.
2. Blood cultures should be obtained before starting antibiotics, but this should not delay treatment.
3. Broad-spectrum intravenous antibiotics should be started within 60 minutes of presentation.

While other investigations (such as chest X-ray and urinalysis) may be helpful, they should not delay the initiation of antibiotic therapy. Observation or oral antibiotics are inadequate for this high-risk patient.

This question tests your knowledge of the management of fever in immunocompromised hosts, which is a crucial concept for the MCCQE1 exam and Canadian medical practice.

References

1. Bow EJ, et al. AMMI Canada Guidelines for the Management of Febrile Neutropenia. Official Journal of the Association of Medical Microbiology and Infectious Disease Canada. 2019.

2. Freifeld AG, et al. Clinical practice guideline for the use of antimicrobial agents in neutropenic patients with cancer: 2010 update by the infectious diseases society of america. Clin Infect Dis. 2011;52(4):e56-e93.

3. Public Health Agency of Canada. "Canadian Tuberculosis Standards 7th Edition: 2014." Available at: https://www.canada.ca/en/public-health/services/infectious-diseases/canadian-tuberculosis-standards-7th-edition.html (opens in a new tab)

4. Kasper DL, Fauci AS, Hauser SL, Longo DL, Jameson JL, Loscalzo J. Harrison's Principles of Internal Medicine, 20e. McGraw-Hill Education; 2018.

5. UpToDate. "Fever in the Immunocompromised Host." Accessed 2023.