DERMATOLOGY

Autologous Serum Skin Test

It is a test developed to reveal the presence of autoantibodies (or histamine releasing factors) in patients with chronic urticaria.

Application

Venous blood is taken from the patient and allowed to clot for 30 minutes at room temperature.

Serum is separated by 500 g centrifugation for fifteen minutes.

After the skin is slightly stretched, 0.05 ml of autologous serum is administered intradermally, with an insulin or tuberculin syringe and with the tip opening of the syringe facing down, on the inner forearms that have been wiped and cleaned with alcohol, at a 45-degree angle. If there are urticarial lesions or lesions in the application area, application should not be made close to these lesions and this should be considered in the evaluation of the results.

Along with the antigen, sterile saline (at the same dose) as negative control or diluent (containing 0.4% phenol as preservative) is administered, again as described above.

Care should be taken to ensure that no air remains in the syringe and that the injected antigen does not go under the skin. An autologous serum and a negative control are injected into the arm, leaving approximately 4 cm between the two. It may be more appropriate to apply the test bilaterally to both arms (especially in terms of evaluating the possibility of false negative reaction by subcutaneous infiltration of the solutions).

Comment

30 minutes after administration, the formation of a red (erythematous) urticarial papule that is 1.5 mm or larger than the negative control is considered as positive.

Before the application, the information and consent form is read and signed by each patient.

Classical antihistamines should be discontinued for at least three days, and long-acting antihistamines, tricyclic antidepressants, and phenothiazine derivatives at least seven days (there is a possibility of false negatives in patients who have been using systemic corticosteroids or immunosuppressive agents for a long time).

In multi-drug allergy syndrome and multi-non-steroidal anti-inflammatory drug sensitivities, the test often gives a positive result.