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Streptococcus pneumoniae (Pneumococcal) Antibody Tests

Test code(s) 16374, 16963, 19564

Question 1. Why measure Streptococcus pneumoniae IgG (pneumococcal) antibodies?

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

Question 2. What do the serologic values mean?

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.

Question 3. What serologic results are typically expected after vaccination?

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.

Question 4. Why do different pneumococcal antibody panels have different numbers of serotypes?

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.

Question 5. Which serotypes are included in the most commonly ordered assays?

  • 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)

Question 6. Which method is used to determine pneumococcal antibody levels?

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.

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.
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 his/her education, clinical expertise, and assessment of the patient.
Document FAQS.181 Version: 1
Version 1 effective 10/19/2017 to present
Version 0 effective 09/26/2016 to 10/19/2017