New advances refine chronic urticaria screening.

SAN ANTONIO -- Treatment of chronic urticaria can be challenging, but recent findings regarding the condition may help improve outcomes, Dr. Aniko Kobza Black reported at the annual meeting of the American Academy of Dermatology.

One new advance that she discussed is the usefulness of the autologous serum skin test (ASST) in screening for autoimmune urticaria.

It is important to keep in mind, however, that positivity on the ASST can persist even after clearing in cases of autoimmune urticaria. With other types of urticaria, the ASST will become negative as the condition improves and resolves, she said.

Another recent finding is the association between a positive ASST and multiple drug sensitivities in patients with acute urticaria, said Dr. Black, who is with the St. John's Institute of Dermatology at St. Thomas Hospital in London.

Yet another interesting new finding "may have practical implications," she said.

With the use of plasma rather than serum in the autologous serum skin test, the positive test rate can be increased from 55% in patients with chronic urticaria to 86%.

"There is an additional factor in plasma that induces histamine release, and it's now been shown that in chronic urticaria there is increased thrombin formation. Thrombin can activate mast cells, so the modulation of the coagulation system with anticoagulants may prove useful in therapy for urticaria," she said.

The role that Helicobacter pylori may play in chronic urticaria is controversial. About 40% of patients have abdominal symptoms, but there is no direct evidence to show that H. pylori infection causes the condition.

It may be that it plays an indirect role in genetically predisposed individuals, but this remains unclear, Dr. Black said.

Still, if patients have severe indigestion, look for and treat H. pylori, she recommended, noting that this doesn't always lead to improvement, but can help in some cases.

First-line treatment for chronic urticaria remains low-sedation antihistamines. A controversial treatment approach is the use of doses above typically recommended levels, which appears to be clinically effective in some patients, but no trials have yet shown efficacy with the approach.

Increasing the dose up to four times the recommended level or combining different antihistamines to achieve these levels are among the approaches used. The latter approach to achieving higher doses may be more practical as pharmacists tend to more readily dispense the drugs separately, she noted.

In rare cases, antihistamines may actually cause worsening of urticaria. Allergic reactions can occur in minutes, but they usually occur after 6 hours, and they have been seen with each type of antihistamine.

No definite cause is known, but the allergic reactions may be the result of a direct effect on mast cells. Dr. Black said that she has seen only eight or so cases of this over the past 25 years.

Second- and third-line treatments play an important role in the chronic urticaria, and can include systemic steroids and immunotherapy.

When making decisions about treatment, first consider potential side effects, then ease of administration, and then cost, she advised.

It is not possible to predict which treatments will be effective in a given patient.

When the first-line antihistamine treatments and combinations are not adequate, it is important to reassess disease severity, patient history, and status on the ASST before trying the second- and third-line treatments because of the risk of side effects.

All three types of treatments can be combined, however, "and indeed they usually have to be," Dr. Black said.

BY SHARON WORCESTER

Southeast Bureau