Diagnostycznie znamienny poziom przeciwciał dla toksyny krztuścowej u dorosłych osób w Polsce
[Establishment of the diagnostic cut-off points for levels of serum antibodies to pertussis toxin in adults in Poland]

STRESZCZENIE

Na podstawie badania próbek surowicy uzyskanych od 236 krwiodawców wyznaczono diagnostycznie znamienny poziom przeciwciał klasy IgG i IgA dla toksyny krztuścowej u osób dorosłych w Polsce. Przeprowadzone badania wykazały, że w przypadku poszukiwania przeciwciał klasy IgG za diagnostycznie znamienny poziom (cut-off) należałoby przyjąć wartość 120 IU/ml, natomiast przy poszukiwaniu przeciwciał klasy IgA wartość 16 IU/ml. Obecność przeciwciał klasy IgG dla toksyny krztuścowej na diagnostycznie znamiennym poziomie wykazano w 18 (7,6%) próbkach, natomiast przeciwciał klasy IgA w 14 (5,9%) próbkach surowicy krwiodawców.

ABSTRACT

Introduction: Standardization of ELISA tests for the diagnosis of infections caused by B. pertussis remains challenging despite efforts to improve it. It is recommended that serology testing should use purified pertussis toxin as the only coating antigen and that concentration of antibodies should be expressed in international units per mL (IU/ml) according to the First WHO International Standard for Pertussis Antiserum. However, available commercial ELISAs are often of different antigen composition and quality and sometimes do not calculate antibody levels in IU/ml. Furthermore, for single-sample serology, various cut-off values for IgG- and IgA-anti pertussis toxin in different EU reference laboratories have been proposed. The aim of this study was to establish of the diagnostic cut-off points for levels of serum IgG and IgA antibodies to pertussis toxin in adults in Poland and determine the seroprevalence of these antibodies among Polish blood donors.
Materials and Methods: The IgG and IgA antibodies in serum samples collected from 236 blood donors were measured by in-house ELISA with purified pertussis toxin as antigen (0,5 μg/ml). The cut-off value was settled by calculation the OD450 results from all blood donors (arithmetic mean plus 2 standard deviations). Antibody levels were quantitated with respect to the First WHO International Standard for Pertussis Antiserum (06/140) and results were expressed in IU/mL.
Results: According to the obtained results, in the case of searching for IgG and IgA antibodies for pertussis toxin, a cut-off of 120 IU/ml and 16 IU/ml respectively, should be taken as diagnostic significant level in the adult population in Poland. A study showed the presence of IgG antibodies at a diagnostic level in 18 (7.6%) samples, and IgA antibodies to pertussis toxin in 14 (5.9%) serum samples obtained from blood donors.
Conclusions: The established in our investigation cut-off values for anti-PT IgG and IgA good correspond with values recommended by reference laboratories in other European countries.

Key words: pertussis, pertussis toxin, diagnostic significant level of antibodies, cut-off, ELISA