Streptococcus pneumoniae (Pneumococcal) Antibody Tests

There are 2 principal reasons to measure pneumococcal IgG antibodies:

1. Estimate pre-existing antibody levels for different pneumococcal serotypes
2. Assess immunologic responses after pneumococcal vaccination

Serologic correlates of protection against pneumococcal disease have not been rigorously established for all patient populations. Published data and expert consensus (including WHO) suggest protection from invasive disease usually occurs at levels ≥0.3-0.50 µg/mL for healthy children receiving pneumococcal conjugate vaccination.^1-4 Higher titers may be necessary to protect from noninvasive infection (eg, pneumonia, otitis, sinusitis). Expert opinion suggests that a cut-off of ≥ 1.3 µg/mL may be a more relevant value to assess antibody responses after pneumococcal polysaccharide vaccines and for immunocompromised patients.⁵ In addition to antibody quantity, protection also depends on antibody avidity and opsonophagocytic activity.

No consensus has been established concerning the percentage of serotypes for which antibody titers should change after vaccination. However, seroconversion or 2- to 4-fold rises in IgG titers for >50% to 70% of vaccine serotypes are considered, by some experts, to demonstrate a normal post-vaccination immune response. If seroconversion or a 2- or 4-fold rise in antibody titers is not demonstrated after vaccination, further assessment of an individual’s immunologic function may be warranted.

The panels include different numbers of serotypes because the different vaccines contain different numbers of serotypes. The most widely recommended vaccines currently include 13 serotypes (eg, pneumococcal conjugate vaccines) or 23 serotypes (eg, polysaccharide vaccines). The panels may also include naturally occurring serotypes, which may cause infection and produce a measurable antibody response even in the absence of pneumonia or other disease.

• Test code 16374; Streptococcus pneumoniae IgG Antibody (13 serotypes), MAID
• Includes serotypes 1, 3, 4, 5, 6 (6A), 14, 19 (19F), 23 (23F), 26 (6B), 51 (7F), 56 (18C), 57 (19A), and 68 (9V)
• Test code 19564; Streptococcus pneumoniae IgG Antibody (14 serotypes), MAID
• Includes serotypes 1, 3, 4, 5, 8, 9 (9N), 12 (12F), 14, 19 (19F), 23 (23F), 26 (6B), 51 (7F), 56 (18C), 68 (9V)
• Test code 16963; Streptococcus pneumoniae IgG Antibody (23 Serotypes), MAID
• Includes serotypes 1, 2, 3, 4, 5, 8, 9 (9N), 12 (12F), 17 (17F), 14, 19 (19F), 20, 22 (22F), 23 (23F), 26 (6B), 34 (10A), 43 (11A), 51 (7F), 54 (15B), 56 (18C), 57 (19A), 68 (9V), and 70 (33F)

Quest Diagnostics^® Infectious Disease uses a multi-analyte immunodetection (MAID) method. The method employs the Luminex^® flow cytometric system, which measures multiple analytes simultaneously. The FDA standard reference serum 89-S is used as the calibration standard. Results are reported in µg/mL.