Invasive pneumococcal disease and investigation of immune deficiency
Invasive pneumococcal disease and investigation of immune deficiency
Invasive pneumococcal disease is defined as isolation of Streptococcus pneumoniae from a normally sterile site e.g: blood, cerebrospinal fluid or joint. These are seen clinically as conditions such as bacteraemic pneumonia, septicaemia, meningitis, arthritis and peritonitis.
Certain groups are recognised to be at particular risk of IPD as shown below:
| Anatomic causes | Cochlear implants Asplenia or functional asplenia Cerebrospinal leaks and anatomic malformations |
| Primary Immunodeficiency | Antibody deficiencies such as: X-linked Agammaglobulinaemia (Bruton's) Complement deficiency |
| Secondary Immunodeficiency | HIV Infection Secondary to malignancy or immune suppressants or transplantation |
| Chronic conditions | Diabetes Down syndrome |
With effective pneumococcal conjugate vaccination there has been a decline in invasive pneumococcal disease (IPD), particularly in infants and young children as well as herd effects (protection of unimmunised individuals) in older age groups.
When a case of IPD happens now, in children it may be due to an undiagnosed primary immune deficiency and warrant immunologic testing.
In the absence of any other known risks, prevalence of primary immune deficiency is higher in children older than 2 years of age presenting with primary IPD and in children with recurrent IPD (1, 2).
Below outlines the investigations suggested in any child regardless of age who presents with invasive pneumococcal disease in the absence of known risk factors.
First-line immune testing recommended for any child who presents with IPD
FBC and blood film (ensure examination not automated and that report comments on absence/presence of Howell Jolly bodies)
Consider performing abdominal ultrasound scan to check for spleen presence
Ig G / A / M
HIV antibody with appropriate maternal consent if no maternal antenatal HIV screen performed nor maternal results able to be reviewed.
Second-line immune testing
In addition to the above, children presenting with the following will require further discussion with immunology
Pneumococcal meningitis
Complicated pneumococcal pneumonia
Unusual sites of pneumococcal infection
Recurrent IPD (2 or more episodes)
History of consanguinity
Additional investigations likely to be suggested by immunology:
Lymphocyte subsets
Vaccine antibody responses:
Step 1: baseline tetanus, diphtheria, Haemophilus influenzae type b and pneumococcal antibodies
Step 2: if any below protective level as defined by testing laboratory, give appropriate booster (e.g. DTaP, Pneumovax if >2 y.o; Synflorix/Prevenar if <2 y.o.)
Step 3: ensure repeat antibody levels are done 4 weeks after boosting
Classic and alternate complement pathway activity, C3 and C4. Recommend discussing optimal timing of this test with the on-call immunologist. In some patients these are best performed on recovery from illness (ideally pre-discharge from tertiary centre or prior to transfer back to regional hospital).
Abnormalities identified from the above tests should be discussed with Immunology.
For all cases of recurrent bacterial meningitis comprehensive neuroimaging will need consideration to examine for underlying anatomic defects causing possible CSF breach/fistula.