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R. Asero, M. Cugno, A. Tedeschi, Autologous plasma and serum skin test in chronic urticaria, British Journal of Dermatology, Volume 166, Issue 6, 1 June 2012, Pages 1362–1363, https://doi.org/10.1111/j.1365-2133.2011.10779.x
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Funding sources: none.
Conflicts of interest: none declared.
Madam, We were surprised to read the study by Yıldız et al.1 about the use of autologous plasma skin test (APST) in patients with chronic urticaria (CU), and would like to comment on some aspects of this issue.
Yıldız et al.1 claim that seven of 42 patients with CU and four of 35 healthy subjects were positive on intradermal testing with sodium citrate diluted with saline solution, and conclude that APST was never positive if evaluated with negative controls. However, their conclusion is undermined by the lack of definition of positivity of intradermal testing with sodium citrate. In our experience, we have not observed any skin reaction to intradermal injection with sodium citrate diluted with saline solution unless the subject shows a marked dermatographism and reacts to saline solution too. If sodium citrate were able to induce nonspecific weal‐and‐flare reactions as claimed by Yıldız et al., one would expect to find a large prevalence of normal subjects scoring positive on APST but, again, this has never been observed in our series2–4 as well as by other authors.5 In the original paper published in the Journal of Allergy and Clinical Immunology,2 to assess the specificity of skin reactions induced by autologous plasma, 10 patients [five positive on autologous serum skin test (ASST) and eight on APST] underwent further intradermal tests using sodium citrate 0·125 mol L−1 in saline; no patient reacted to this solution. In particular, three of the 10 patients tested were APST positive and both ASST and sodium citrate negative. Moreover, no skin reactivity to APST was observed in 10 subjects with allergic rhinitis, or in five subjects with contact dermatitis.
