Serology

The serology is the description and possibly the proportioning of specific antibodies. It is thus related to the study of the immunoglobulin S of the Sérum Sang uin or others liquid organics. It is used as tool diagnosis, as tool for tracking (AIDS, Hépatite,…) and like epidemiologic tool.

Procedure

Serology is carried out on a venous blood sample (in general with the fold of the elbow). It is not essential to be with jeun. To establish a diagnosis, two taking away separated by two to four weeks are often useful to show a rise marking a recent infection. Trackings require only one taking away in general.

Principle

Generally, serology consists in evaluating immunity with a disease by measuring the quantity of specific antibodies of this one. It can be also used to make sure of the effectiveness of a vaccination (it is the case for example for the Hépatite B). It can finally be used for the diagnosis of a disease auto-immune.

The antibodies evolve/move after a contact with the disease. The first antibodies produced, after the latency time, belong to the class of IgM (immunoglobulin M). Those leave place to another class gradually, IgG (immunoglobulin G) which are longer produced. In the case of a réinfection with the same disease-causing agent, the rate of IgG réaugmente brutally by a phenomenon report of the pathogenic one. The latency times and the ratchet effect are different according to the diseases.

Serology is not applied for all the infections, a nonexhaustive list is proposed hereafter:

Viral serology

See the List of viral serologies

Bacterial serology

  • Salmonelloses
  • Syphilis
  • Streptocoques: Anti StreptoLysines O and Anti streptodornase B

Parasitic serology

  • Toxoplasmose

Determination of the immunizing statute for vaccination

  • serology VZV before vaccination at the health workforces (vaccine nonavailable in France)
  • serology VHA before vaccination at the subjects at the risk
  • quantitative serology VHB after vaccination to check the effectiveness of the vaccine
  • serologies polio and ROR possibly before and after vaccination at immunodéprimés the

Techniques

There exist many techniques of detection of the antibodies:
  • Precipitation in liquid medium or solid medium
  • Agglutination passivates
  • Fixation of the complement
  • Inhibition of the hemagglutination
  • Neutralization (of a property of the antigen)
  • Immunofluorescence
  • Immuno-enzymologie (ELISA: Enzyme Linked Immunosorbent Assay)
      • indirect
    • ELSA
    • ELISA sandwich
    • ELSA competition
  • Western-blot
  • Radioimmunology (in particular for hormonal proportionings)
The sensitivity and specificity vary from a technique to another, therefore influential on the choice of the technique selected. For a tracking one seeks to have very few negative forgeries, this is why a more significant technique will be developed. Conversely for a confirmation, one seeks to have very few false-positives, thus a more specific technique will agree better.

Positive or negative serology

Sometimes the immunizing answer to a infection utilizes the creation of Anticorps.

The presence of antibodies specific to a disease indicates that the person, at one time given in the past, was infected by the disease or simply came into contact with the disease-causing agent. It is said that the person has a positive serology , or is HIV positive . Conversely, the absence of antibody usually states that the person was not contaminated, the person is known as séronégative .

It is about an indirect method since she does not seek the presence of the disease-causing agent but the answer of the immune system against this disease-causing agent.

Since the discovery of HIV by the public opinion in the middle of the Years 1980, the “HIV positive” term indicates in the language running a person who obtained a positive test with a test of protein detection connected with HIV (ELISA or Blot Western). A positive test confirmed by Western blot means that the subject was contaminated by virus HIV, or, more exactly, that following a contact with this virus, its immune system manufactured antibodies. Indeed, this test explores only the presence of antibody and not directly that of the virus. In the absolute, the term is not specific to HIV. When one says for example of an expectant mother that it is HIV positive for the toxoplasmose, that means that it already was in contact with the toxoplasmose and that there is no more risk that she again has it during this pregnancy.

In the same way for the autoimmune diseases, the presence of an autoimmune antibody will be indicated by the term of seropositivity and its absence by the term of seronegativity. The poyarthrites rhumatoïdes are thus said HIV positive when the search for antibody called factor rhumatoïde is present.

Seroconversion

The Séroconversion is the passage of a seronegativity to a seropositivity. This term is often used in Obstétrique or fetal Médecine to indicate the date of which has occurred of an infection for example the Toxoplasmose. Thus the consequences of a seroconversion on the Fœtus depend on the term of the Grossesse or the age gestationnel of the fetus.

See too

  • Blood serum
  • medical Laboratory
  • Seroconversion

External bond

  • Serology - MedlinePlus Medical Encyclopedia
  • Serology

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