Haemophilus influenzae


Indications for Testing

Laboratory Testing

  • CDC - testing recommendations
  • Rapid antigen detection tests are available – utility is questionable
  • Otitis/sinusitis – clinical diagnosis; laboratory testing not routinely performed
  • Pneumonia – CBC, chest x-ray; consider sputum culture, blood culture
    • Positive upper respiratory culture does not necessarily establish organism as pathogen due to colonization
  • Cellulitis – wound culture; consider CBC, depending on clinical severity
  • Meningitis – CBC, spinal tap with CSF culture and gram stain, cell count, and culture
  • Immunoglobin deficiency testing
    • IgG testing for diphtheria, tetanus and H. influenzae – determine vaccination response to diagnose immunoglobulin deficiency in patients with recurrent infection
      • Need pre- and post-vaccine titers (1 month after vaccination)

Differential Diagnosis

Clinical Background

Haemophilus influenzae causes diseases predominantly affecting children.


  • Incidence
    • WHO – 3,000,000 cases of serious disease annually
  • Age – usually in children; exception is pneumonia, which affects all ages  
  • Transmission – respiratory droplet or direct contact with secretions


  • Small, nonmotile, nonspore-forming, fastidious gram-negative bacterium
  • Requires medium containing X (porphyrins such as hemin) and V (nicotinamides such as NAD) factors for aerobic growth (eg, chocolate agar)
  • Six major typable serotypes (A-F)
    • Nontypeable strains are common
  • Colonizes human upper airways
    • Up to 80% of healthy people carry nontypeable H. influenzae

Clinical Presentation

  • Otitis media, sinusitis, pharyngitis – usually children
  • Cellulitis – predominantly young children
  • Pneumonia – elderly, patients with chronic obstructive pulmonary disease (COPD), and patients who are immunocompromised
    • Common etiology of COPD exacerbations
  • Meningitis – often preceded by symptoms of upper respiratory tract infection, head trauma or surgery, CSF leak, otitis or sinusitis
  • Epiglottitis – usually children
  • Sepsis – neonatal and maternal sepsis
  • Septic arthritis – usually children <2 years
  • Conjunctivitis – may occur in outbreaks, especially in daycare settings


  • Parenteral antibiotics are recommended for serious infections; oral antibiotics can be used for non-invasive disease
    • 30% of isolates produce β-lactamase


  • Vaccination

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Diphtheria, Tetanus, and H. Influenzae b Antibodies, IgG 0050779
Method: Quantitative Multiplex Bead Assay

Determine patient response to vaccine and whether protective antibody levels have been reached

Determines IgG antibody titers to tetanus and diphtheria toxoids and H. influenzae PRP simultaneously


If concentrations of IgG, IgM, and IgA range from low to normal and antibody deficiency is still strongly suspected, determine IgG subclass and response to protein antigens (eg, diphtheria, tetanus toxoid, influenzae) as well as to pure polysaccharide antigens (eg, unconjugated pneumococcal vaccine)

CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential

Evaluate for possible infectious process

Cell Count, CSF 0095018
Method: Cell Count/Differential

Evaluation of white blood cell count and differential in suspected infectious meningitis/encephalitis

Respiratory Culture and Gram Stain 0060122
Method: Stain/Culture/Identification

Determine type of organism involved in pneumonia

Blood Culture 0060102
Method: Continuous Monitoring Blood Culture/Identification

Identify organisms causing bacteremia

Testing is limited to the University of Utah Health Sciences Center only

Cerebrospinal Fluid (CSF) Culture and Gram Stain 0060106
Method: Stain/Culture/Identification

Identify etiology of bacterial meningitis

Additional Tests Available
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
Haemophilus influenzae b Antibody, IgG 0050542
Method: Quantitative Multiplex Bead Assay