Autologous serum skin test in chronic idiopathic urticaria

Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at LSU (Shreveport) Department of Allergy and Immunology

A 21-yo AAF with a long history of chronic idiopathic urticaria and angioedema is referred to the allergy clinic of an academic center for further work-up. Her symptoms started 6 years ago and progressively worsened during the last 2 years to the point where she has had daily hives. She also complains of episodes of angioedema affecting the lids and lips about 4 times per month. She has been taking courses of oral prednisone every 6 weeks for the last 6 years.

Past medical history

Chronic idiopathic urticaria and angioedema for 6 years. Skin prick test (SPT) positive for trees, grass, weeds and molds. Negative extensive work-up for urticaria in the last year.


Allegra (fexofenadine) 180 mg po bid, cetirizine (Zyrtec) 10 mg po qhs, doxepin 50 mg po qhs, Zantac (ranitidine) 150 mg po bid, Benadryl (diphenhydramine) 50 mg po bid prn, Singulair (montelukast) 10 mg po qhs.

Family medical history (FMH)

Mother with food allergies.

Social history (SH)

No tobacco exposure, she has 2 dogs.

Physical examination

Vital signs table (VSS).
Skin: Hives on both arms and abdomen.
HEENT: normal.
Lymph: No lymphadenopathy.
Respiratory: CTA (B).
CVS: Clear S1S2.
Ext: no c/c/e.

What tests would you suggest?

Autologous serum skin test (ASST).
Anti-FcERI antibody (high affinity IgE receptor).
Skin biopsy.

How to do an autologous serum skin test (ASST)?

Blood was collected from the patient and divided into 2 portions, one of which was in a heparinized tube and the other was in a regular tube. Both tubes were centrifuged for 10 minutes and plasma and serum were obtained. Skin prick testing was done with saline, histamine, plasma and serum. Subsequently, intradermal testing was done with plasma and serum. All tests were negative apart from the positive control.

Prick testLeft arm
Wheal (mm)
Left arm
Flare (mm)
Saline0 x 00 x 0
6 x 5
30 x 45
0 x 00 x 0
0 x 01 x 1

Table 1. Results of autologous serum skin test (ASST)

What happened next?

Pending the skin biopsy result, the option of treatment with cyclosporine was discussed with the patient.

Final diagnosis

Chronic idiopathic urticaria and angioedema.

What did we learn from this case?

How to perform an autologous serum/plasma skin test in a patient with chronic idiopathic urticaria (CIU).

A patient is injected with:

1. Control (saline) - no reaction.
2. Their own serum - no reaction.
3. Their own plasma - reaction, proves autoantibody presence.

The ASST consists of an intradermal injection of 0.03 to 0.05 mL of the patient's own serum. The test is positive if the wheal is 1.5 mm greater than the negative control (saline) after 15 minutes.

The autologous plasma skin test (APST) is performed with plasma anticoagulated with 0.125 mol/L of sodium citrate and then centrifuged.

The autologous serum/plasma skin test is not commonly used. The positive and negative predictive values of the autologous serum skin test (ASST) in CIU patients are 53 and 70%, respectively.

27-50% of patients with CIU have autoantibodies against the α-chain of the high-affinity IgE receptor (FceRI) or less commonly against IgG. A positive autologous serum skin test (ASST) is an in-vivo test which reflects the presence of anti-FceRI and/or anti-IgE autoantibodies capable of activating mast cell degranulation.

According to some authors, a positive ASST increases the likelihood that a patient may need long-term oral steroids or cyclosporine in order to control the symptoms of CIU.

Mind map diagram of chronic urticaria (click to enlarge the image).

Diagnosis of Chronic Urticaria (click to enlarge the image).

Anti-FceR1 autoantibodies in chronic autoimmune urticaria: IgG against FceRI (receptor for IgE) (click to enlarge the image).


The autologous serum skin test in a cohort of chronic idiopathic urticaria patients compared to respiratory allergy patients and healthy individuals. Guttman-Yassky E, Bergman R, Maor C, Mamorsky M, Pollack S, Shahar E. J Eur Acad Dermatol Venereol. 2007 Jan;21(1):35-9.
AAAAI Q&A on Chronic Urticaria, Ask the Expert, 2002.
Urticaria: A Short Review. Allergy Cases, 2008.
Chronic Idiopathic Urticaria. Allergy Cases, 2008.
Anti-FceR1 Autoantibodies in Chronic Urticaria
Chronic Idiopathic Urticaria. Current Opinion in Allergy and Clinical Immunology, Medscape, 2003.
Tests for "autoimmune" urticaria - AAAAI Ask the Expert, 2011.

Published: 08/19/2008
Updated: 11/19/2011


cinthia said...

what the proportion of blood and heparina

Anonymous said...

There is no heparin.

The autologous plasma skin test (APST) is performed with plasma anticoagulated with 0.125 mol/L of sodium citrate and then centrifuged.

Anonymous said...

what does it mean if serum test is positive or plasma test is possitive? do both have the same significance