Comparison of commercially available immunoblot assays measuring IgG and IgA antibodies to Bordetella pertussis antigens

Abstract

Bordetella pertussis infection is mostly diagnosed by serological tests, such as by enzyme-linked immunosorbent assays (ELISAs) or by immunoblots. We compared immunoblots from five different manufacturers. Immunoblots from Euroimmun, Mikrogen, Trinity Biotech, Viramed and Virotech were used. All kits except the kit from Trinity Biotech measured IgG and IgA antibodies separately. The kits were used according to the kit inserts. Various reference preparations from the World Health Organization (WHO), the National Institute for Biological Standards and Control (NIBSC) and the Center for Biologics Evaluation and Research/Food and Drug Administration (CBER/FDA) were analysed. Patient sera with high antibody titres in ELISA, sera from patients with compatible clinical symptoms and sera from vaccinees were compared. An algorithm for interpreting quantitative values for IgG and IgA anti-pertussis toxin (PT) from in-house ELISAs was used as a reference. The sensitivity and specificity of the assays was variable when comparing the qualitative results of immunoblots with expected values of reference preparations and ELISA interpretation of patient sera. The interpretation of semi-quantitative reading of the immunoblots did not compare well to the ELISA results. Adenylate cyclase toxin as an additional antigen in two immunoblots did not effectively distinguish between infection and vaccination. Due to the lack of quantification of antibody concentrations, IgG and IgA immunoblots are of limited value in the serological diagnosis of pertussis.

Clinical Definitions of Pertussis: Summary of a Global Pertussis Initiative Roundtable Meeting, February 2011

“…High levels of IgA and/or IgG antibodies to PT were described in many studies of prolonged cough illness as an accurate indicator of recent pertussis disease [21, 22, 24–29]. In Europe, single-serum serology for the diagnosis of pertussis has been intensively studied in the Netherlands [30], and commercial test kits with a variety of pertussis antigens and varying degrees of sensitivity and specificity are available [31]. EU reference laboratories have recently suggested recommendations for the serologic diagnosis of pertussis; these include mainly quantifying IgG antibodies to PT and reporting results in international units/mL [32, 33].…”

High frequency of pertussis in older children and adolescents with prolonged cough in Turkey

“…Common laboratory diagnostic tests currently include culture, PCR and serologic study on acute and convalescent-phase sera. Sensitivity and specificity of the tests depends on the age of the patient, time from symptom onset, vaccination and exposure history, specimen collection and test procedure 18 .…”

“…However, diagnosing pertussis using commercial serological kits is problematic 18 . The serologic tests are not well standardized; the accuracy of test result varies between different kits, and the variety of antigens used 20 .…”

“…PCR is a rapid test and has excellent sensitivity 18 . For PCR, the optimal timing for specimen collection is the first 3 weeks of cough, but bordetella DNA may be detected by PCR for 4 weeks after cough onset 18,23 . After the fourth week of illness, the amount of bacterial DNA rapidly diminishes, which increases the risk of obtaining falsely-negative results.…”

“…After the fourth week of illness, the amount of bacterial DNA rapidly diminishes, which increases the risk of obtaining falsely-negative results. In vaccinated children, adolescents and adults with cough illness of ≤3 weeks' duration, PCR is the only appropriate method for diagnosis of pertussis 18,30,31 . A PCR method with high sensitivity such as IS481 is ideal for the evaluation of sporadic coughing illness in the age groups who are almost always either previously immunized against or exposed to B. pertussis 30 .…”