How is malaria diagnosed and managed in the UK?

Malaria Diagnosis and Management in the UK

Malaria diagnosis in UK emergency departments requires a combination of microscopic examination of thick and thin blood films, rapid diagnostic tests (RDTs), and clinical assessment, with treatment based on Plasmodium species identification and severity assessment. 1, 2

Diagnostic Approach

Clinical Suspicion

• Malaria should be considered in any patient presenting with fever who has traveled to an endemic area, particularly sub-Saharan Africa 1
• Most patients present with:
  • Fever or history of fever (90% sensitivity) 1
  • Headache, myalgia, arthralgia, and malaise 1
  • Gastrointestinal or respiratory symptoms may be present 1
• Important laboratory findings that increase suspicion:
  • Thrombocytopenia (<150,000/μL) - present in 70-79% of cases 1
  • Hyperbilirubinaemia (>1.2 mg/dL) 1

Diagnostic Testing Algorithm

1. Initial Testing:

   • Thick and thin blood films stained with Giemsa or May-Grunwald-Giemsa (gold standard) 1, 2
   • Rapid diagnostic tests (RDTs) performed simultaneously 1, 2
   • Direct liaison with laboratory to ensure urgent processing 1

2. Repeat Testing:

   • Three negative blood films/RDTs over 72 hours are required to confidently exclude malaria 2
   • If clinical suspicion remains high despite negative initial tests, repeat testing should be performed daily 3

3. Confirmatory Testing:

   • Positive samples should be sent to reference laboratory for confirmation 2
   • PCR may be used to confirm diagnosis, characterize mixed infections, or diagnose submicroscopic parasitemia 3

Diagnostic Test Performance

• Microscopy (gold standard):

  • Allows species identification, quantification of parasitemia, and differentiation between sexual/asexual forms 1
  • Requires skilled personnel, which can be challenging in non-endemic settings 1

• RDTs:

  • For P. falciparum: Sensitivity 67.9-100% (mean 91.8%), Specificity 98.1-100% 1
  • For P. vivax: Sensitivity 66-91%, Specificity 98.1-100% 1
  • In children, RDTs have 100% sensitivity for P. falciparum but lower sensitivity for other species 4
  • Used increasingly in UK laboratories, especially during on-call hours 5

Severity Assessment

Criteria for Severe Malaria

Presence of any ONE of the following indicates severe malaria requiring urgent treatment 1, 2:

• Depressed consciousness (of any degree)
• Status epilepticus
• Respiratory distress or hypoxia (O₂ saturation <95%)
• Evidence of shock
• Metabolic acidosis (base deficit >8)
• Severe hyperkalemia (potassium >5.5 mmol/L)
• Hemoglobin <100 g/L
• Hyperparasitemia >5%
• Visible jaundice

Management

Emergency Management

For severe malaria (medical emergency) 1:

1. Initial Assessment:

   • Follow APLS (Advanced Paediatric Life Support) structured approach
   • Assess airway, breathing, circulation, disability, exposure

2. Immediate Treatment:

   • First-line treatment: Intravenous artesunate 2
   • If artesunate unavailable: IV quinine dihydrochloride (20 mg/kg diluted in 20-40 ml over 4 hours) 1
   • Admit to intensive care unit for close monitoring 2

3. Supportive Care:

   • Oxygen therapy if hypoxic
   • Volume resuscitation if in shock (20 ml/kg of colloid or 0.9% saline) 1
   • Monitor blood glucose (hypoglycemia is common) 2
   • Treat seizures if present

Uncomplicated Malaria Treatment

1. First-line treatment: Oral artemisinin-based combination therapy (ACT) 2
2. Alternative options:
   • Atovaquone-proguanil
   • Quinine plus clindamycin for chloroquine-resistant malaria 2, 6
3. For P. vivax and P. ovale:
   • Add primaquine or tafenoquine to eliminate liver hypnozoites 2

Common Pitfalls to Avoid

1. Delayed diagnosis - Can lead to life-threatening disease; any febrile traveler from endemic areas should be tested promptly 1, 2

2. Inadequate testing - A single negative blood film does not exclude malaria; three tests over 72 hours are required 2, 3

3. Misinterpreting RDT results - False negatives can occur with:

   • Non-falciparum species
   • Low-level parasitemia
   • P. falciparum strains with pfhrp2/3 gene deletions 4
   • Prozone-like effect (very rare) in extremely high parasite densities 7

4. Relying on RDT line intensity for parasite density - RDTs should not be considered quantitative, especially in high-density infections 7

5. Delaying treatment - If clinical suspicion is high, empiric treatment should be started even while awaiting confirmation 1, 3