Can a Haemophilus influenzae type b (Hib) titer be checked?

Haemophilus influenzae Type b (Hib) Titer Testing

Yes, Haemophilus influenzae type b (Hib) titers can be checked, but this is only recommended for specific high-risk populations and not for routine assessment of immunity in the general population. 1

When Hib Titer Testing is Appropriate

Hib antibody titers may be checked in the following situations:

High-Risk Individuals

• Patients with functional or anatomic asplenia (including sickle cell disease) 1
• Patients with HIV infection 1
• Patients with immunoglobulin deficiency (including IgG2 subclass deficiency) 1
• Patients with early component complement deficiency 1
• Recipients of hematopoietic stem cell transplants 1
• Patients receiving chemotherapy or radiation therapy for malignant neoplasms 1

Special Clinical Scenarios

• Children under 24 months who have had invasive Hib disease (to determine if revaccination is needed) 1
• Evaluation of suspected primary immunodeficiency disorders 1
• Assessment of vaccine response in immunocompromised patients 1

Interpretation of Hib Titers

• Protective antibody levels are generally considered to be ≥1.0 μg/mL of anti-polyribosyl ribitol phosphate (PRP) antibodies 2
• Some studies consider ≥0.15 μg/mL as providing some protection 2
• Interpretation should be made in the context of the patient's vaccination history and immune status

Clinical Implications of Titer Results

Low Titers

• In immunocompromised patients with low titers, revaccination may be considered 1
• HIV-infected patients with low titers may benefit from additional doses of Hib vaccine 2
• Patients undergoing chemotherapy with low titers should be considered unimmunized and may require revaccination after completion of therapy 1

Normal Titers

• Indicate adequate protection against invasive Hib disease
• No further intervention needed in immunocompetent individuals

Important Considerations

• Unlike hepatitis B titers, routine monitoring of Hib antibody levels is not recommended for the general population 1
• There is no consensus on the interpretation of results or implications for revaccination except in specific high-risk groups 1
• For hematopoietic stem cell transplant recipients, Hib vaccination should be administered regardless of pre-transplant titers 1
• Children with chronic renal failure may have protective titers after vaccination but might require monitoring 1

Pitfalls to Avoid

1. Don't routinely check Hib titers in healthy, immunocompetent individuals who have completed their primary vaccination series
2. Don't assume that a low titer automatically indicates need for revaccination in all populations
3. Don't forget that natural exposure to Hib or cross-reactive organisms may provide immunity even without vaccination
4. Don't delay appropriate vaccination while waiting for titer results in high-risk individuals

In summary, while Hib titers can be checked, they are primarily useful in specific high-risk populations and not recommended as a routine test for the general population. The decision to test should be based on clinical context and risk factors for invasive Hib disease.