BackgroundTitanium is being increasingly used. Although it is considered to be a non‐allergenic material, allergic reactions to it have been reported. Titanium dioxide has been found to be an unreliable patch test material. Few studies to date have profiled titanium allergy, and it therefore remains difficult to distinguish its manifestations.ObjectivesTo evaluate alternatives for titanium dioxide as a patch test preparation, and to profile titanium reactions and manifestations.MethodsA retrospective chart review was conducted with 458 patients who underwent patch testing with at least 1 of 5 different titanium salts.ResultsAt least 1 positive result was noted in 5.7% of the patients. The frequency of positive results for the tested salts ranged from 0.9% to 7.9%. Titanium(IV) oxalate hydrate had the highest yield and titanium dioxide the lowest. Erythema, dermatitis and local swelling were the most common objective complaints. In 16 (61.5%) patients, the test result had partial or full clinical relevance.ConclusionsNo titanium‐specific risk factors and clinical picture could be identified. Titanium dioxide is not adequately sensitive for identifying titanium allergy. The titanium salts seem to be possible superior patch test preparations, but appear to be unsuitable if used singly. The patient's medical history and clinical picture remain crucial in the diagnostic work‐up.

Background: Skin patch testing is still seen as the gold standard for the diagnosis of allergic hypersensitivity. For several metals and for patients with a suspected adverse reaction to their medical device implant material, patch testing can be unreliable. The current alternative to metal allergy patch testing is the in vitro lymphocyte proliferation test (LPT) using tritiated thymidine. This method is well-established but requires handling of radioactive material, often uses heat-inactivated allogenic human pooled serum and cannot determine T cell subsets. Objective: To develop a radioactive free LPT by using carboxyfluorescein succinimidyl ester (CFSE) and to evaluate the influence of serum source (heat-inactivated human pooled serum [HI HPS] vs autologous serum) on the sensitivity and specificity of the nickel-specific LPT. Methods: Peripheral blood mononuclear cells derived from nickel-allergic patients and healthy controls were collected, labelled with CFSE and cultured in medium containing 10% HI HPS or 10% autologous serum with or without additional T cell skewing cytokine cocktails (Th1: IL-7/IL-12, Th2: IL-7/IL-4 or Th17: IL-7/IL-23/IL-1β) in the absence or presence of NiSO 4 . The stimulation index (SI) was calculated as the ratio of divided cells, that is the percentage of CFSE low/neg CD3 + CD4 + T-lymphocytes upon nickel stimulation compared to the percentage of CFSE low/neg CD3 + CD4 + T-lymphocytes without antigen. These results were compared with the history of Ni allergy, patch test results and the MELISA test.Results: Autologous serum positively influenced Ni-specific proliferation while HI HPS negatively influenced Ni-specific proliferation. The test protocol analysing CD4 + cells and autologous serum without skewing cytokines scored the best diagnostic values (sensitivity 95%; specificity 93%; and overall accuracy 94%) compared to the parallel test using HI HPS (accuracy 60%). Cytokine supplements did not further improve the test protocol which used autologous serum. The protocol using HI HPS could be further improved by addition of the cytokine skewing cocktails. | 723 de GRAAF et Al.