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Newly published data show routine testing is unlikely to change the management of patients with CSU.
New data suggested that while routine testing of patients with chronic spontaneous urticaria (CSU) may reveal elevated plasma D-dimer levels in a subset of patients, such findings are unlikely to make a difference in the overall management of patients.
Authors Sujoy Khan, MBBS, and Rebecca Avison, both of the United Kingdom’s Hull University Teaching Hospitals NHS Trust, wrote in response to a 2019 study in the same journal, which found that elevated plasma levels of D-dimer could influence treatment options but not the overall management of patients.
Khan and Avison reported the findings of a quality improvement project they recently undertook to determine the usefulness of routine testing in CSU. The project was based on British Society of Allergy and Clinical Immunology guidelines, and was divided into 2 phases: the first involved 169 patient consultations for 7 months between September 2018 and March 2019; the latter involved 190 consultations for 4 months between September and December 2019.
In the first phase, 763 blood tests were performed on 44 patients, with an average age of 42.6 years. Of those, only 12 tests were abnormal, and just 2 (0.3%) resulted in a change in patient management. Ninety-three immunoglobulin E (IgE) tests were performed and 14 patients underwent skin tests, three-quarters (71%) of which were either dermographic or negative.
“The positive specific IgE tests were to aero-allergens such as house dust mite or animal dander that were identified on skin tests but patients felt that this was not new information,” the investigators wrote.
Nearly all patients had tests for 25-hydroxy-vitamin D3 levels and vitamin B12, folate, and ferritin levels (84% and 87%, respectively). The overall cost of testing the patients was at least $2,400. The phase 1 findings resulted in changes to the NHS’ Directory of Services for Immunology.
Phase 2 included 30 patients with CSU and angioedema. Those patients underwent 262 tests, including 73 specific IgE tests, resulting in just 21 abnormal results and 1 (0.4%) patient management change.
Positive tests were due to similar causes as those identified in the first phase, and again did not affect patient management. This time the patients were not given skin prick testing, nor were 25-hydroxy-vitamin D3 or hematinics tests requested. That brought the cost down to roughly $800, the authors said.
“In conclusion, there was no evidence that routine testing in the evaluation of CSU made any change in treatment or that patient safety is likely to be compromised if no tests were offered, if the clinical history was accurate,” Khan and Avison concluded.
Given the lack of an apparent clinical benefit, the investigators offered theories as to why physicians offer the tests. It could be due to pressure to rule out secondary triggers, a desire to reduce patient anxiety, conflicting opinions about triggers, or the tendency to generalize reports that have identified biomarkers in some types of CSU.
“We hope this additional data will be of value in convincing caregivers that routine testing in patients with CSU is of low benefit and only adds to the ongoing costs of therapy,” they said.
The research letter, "Routine testing not beneficial in evaluation of patients with chronic spontaneous urticaria," was published online in the Indian Dermatology Online Journal.