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Streptococcus pneumoniae (Pneumococcal) Antibody Tests

Test codes: 16374, 16963, 19564

There are 2 principal reasons to measure pneumococcal IgG antibodies:

  1. Estimate pre-existing antibody levels for different pneumococcal serotypes
  2. Assess immunologic responses before and after pneumococcal vaccination, which is particularly useful in the evaluation of immune deficiency syndromes

Antibody based assays are not optimal for diagnosis of active infection and instead direct-detection methods are recommended (eg. bacterial culture, antigen test).

Quest Diagnostics uses a multi-analyte immunodetection (MAID) method. The method employs the Luminex® flow cytometric system, which measures multiple analytes simultaneously. The WHO standard reference serum 007sp is used as the calibration standard. Results are reported in µg/mL.

The panels include different serotypes based on what is included in select 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. Below are the serotypes included in the listed tests.

  • Streptococcus pneumoniae IgG Antibody (13 serotypes), MAID (test code 16374)
    Includes serotypes 1, 3, 4, 5, 6 (6A), 14, 19 (19F), 23 (23F), 26 (6B), 51 (7F), 56 (18C), 57 (19A), and 68 (9V). 

This test code includes serotypes found in Prevnar 13 (PCV13).

  • Streptococcus pneumoniae IgG Antibody (14 serotypes), MAID (test code 19564)
    Includes serotypes 1, 3, 4, 5, 8, 9 (9N), 12 (12F), 14, 19 (19F), 23 (23F), 26 (6B), 51 (7F), 56 (18C), and 68 (9V)
  • Streptococcus pneumoniae IgG Antibody (23 Serotypes), MAID (test code 16963)
    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). 

This test includes serotypes found in Pneumovax (PPSV23). 

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 cutoff 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 regarding the criteria for evaluating changes in antibody levels 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.6 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.

For immune deficiency syndromes, the criteria for diagnosis include assessing pneumococcal antibody levels pre- and post-vaccination 4 to 8 weeks apart.5,6

Interlaboratory variability for multiplexed immunoassays may be serotype dependent and due to differences in specific procedural steps, source and lot of antigen or reagents, and bead coupling methods.7 However, the clinical interpretation when applying cutoff criteria to determine protective immunity remains consistent between laboratories when evaluating all serotypes.8,9 Therefore, results from paired serum samples (pre- and post-vaccination) are best interpreted if performed by the same laboratory using the same methodology.

A multilaboratory assessment among 3 large reference laboratories demonstrated wide variation between laboratories and between serotypes, with correlation coefficients, r values, ranging from 0.22 (low correlation) to 0.96 (high correlation). The study also suggests that the impact of interlaboratory variability can be mitigated by using paired serum (pre- and post-vaccination titers measured by the same laboratory as opposed to single measurement) and less-stringent vaccine response criteria (2-fold vs 4-fold increase in titers).9

References

  1. Plotkin SA. Correlates of protection induced by vaccination. Clin Vaccine Immunol. 2010;17:1055-1065.
  2. Balmer P, Cant AJ, Borrow R. Anti‐pneumococcal antibody titre measurement: what useful information does it yield? J Clin Pathol. 2007;60:345-350.
  3. Rennels MB, Edwards KM, Keyserling HL, et al. Safety and immunogenicity of heptavalent pneumococcal vaccine conjugated to CRM197 in United States infants. Pediatrics. 1998;101:604–611.
  4. Black S, Shinefield H, Fireman B, et al. Efficacy, safety and immunogenicity of heptavalent pneumococcal conjugate vaccine in children. Pediatr Infect Dis J. 2000;19:187-195.
  5. Bonilla FA, Khan FA, Bernstein DA, et al. Practice parameter for the diagnosis and management of primary immunodeficiency. Journal of Allergy and Clinical Immunology 2015;136:1186-1205.e78.
  6. Orange JS, et al. Use and interpretation of diagnostic vaccination in primary immunodeficiency: a working group report of the Basic and Clinical Immunology Interest Section of the American Academy of Allergy, Asthma & Immunology. J Allergy Clin Immunol. 2012;130(3 Suppl):S1-24. doi:10.1016/j.jaci.2012.07.002
  7. Meek B, et al. Multilaboratory Comparison of pneumococcal multiplex immunoassays used in immunosurveillance of streptococcus pneumoniae across Europe. mSphere. 2019;4(6):e00455-19. doi:10.1128/mSphere.00455-19
  8. Zhang X, et al. Impact of analytical variability on clinical interpretation of multiplex pneumococcal serology assays. Clin Vaccine Immunol. 2013;20(7):957-61. doi:10.1128/CVI.00223-13
  9. Daly T, Pickering J, Zhang X, Prince H, Hill H. Multilaboratory assessment of threshold versus fold-change algorithms for minimizing analytical variability in multiplexed pneumococcal IgG measurements. Clinical and Vaccine Immunology. 2014;21:982-988.

 

This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on the physician’s education, clinical expertise, and assessment of the patient.

 

Document FAQS.181 Version: 2

Version 2 effective 08/28/2026 to present

Version 1 effective 10/19/2017 to 08/28/2026
Version 0 effective 09/26/2016 to 10/19/2017

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