Medical expert of the article
New publications
Diphtheria: antibodies to diphtheria toxin in the blood
Last reviewed: 04.07.2025
All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
The causative agent of diphtheria, Corynebacterium diphtheriae, was isolated in pure form by Loeffler in 1884. Corynebacterium diphtheriae is polymorphic. In recent years, a sharp increase in diphtheria has been noted. Diagnosis of diphtheria is based on clinical and epidemiological data. To confirm the diagnosis, a bacteriological study is used to identify the etiologic factor - Loeffler's bacillus. The causative agent of diphtheria can be isolated after 8-12 hours if the patient has not taken antibacterial drugs. However, it should be taken into account that when treating with antibiotics (especially penicillin or erythromycin), before taking material for bacteriological examination, bacterial growth may not be obtained for 5 days (or there is no growth at all). In these cases, serological diagnostic methods are used.
Serological methods for diagnosing diphtheria include the indirect hemagglutination reaction and ELISA. The titer of antibodies to diphtheria toxin is determined at the onset of the disease (1-3 days) and after 7-10 days; an increase in the titer of antibodies by at least 4 times is considered diagnostic. RPGA is highly sensitive and specific. In recent years, RPGA has been replaced by the ELISA method, which has even greater sensitivity and specificity.
When identifying a contingent for vaccination, the antibody titer is determined before vaccination; if it is low or antibodies are absent, patients are indicated for vaccination; its effectiveness is judged by the increase in the antibody titer after vaccination. The main goal of active immunization is to develop specific immunity. Anatoxin serves as an insurmountable barrier to diphtheria toxin and protects the body from intoxication.
Determination of the titer of antibodies to diphtheria toxin is necessary for the diagnosis of diphtheria infection, assessment of the immune tension in subjects, and assessment of the effectiveness of vaccination with diphtheria vaccine.
Titres of antitoxic antibodies characterizing the degree of susceptibility to diphtheria
AT titer, IU/ml |
Interpretation of the result |
Less than 0.01 |
The subject is susceptible to diphtheria |
0.01 |
Minimum level of circulating antibodies that provides some protection |
0.01-0.09 |
Circulating antibody levels that provide some protection |
0,1 |
Protective level of circulating antibodies |
≥1.0 |
Antitoxin level that provides long-term immunity to diphtheria |
[