D3.88 - 5-Year Metal Patch Testing Analysis of a Portuguese Immunology an Allergology Center: Allergen relevance and Cluster identification

Up to 15% of the global population may be allergic to metals. We aim to analyze 5 years of patch tests (PT) to metals in our department.

Retrospective study of tests (2020-2024) using our 58-hapten metal patch series (chemotechnique®). Readings were performed at 48 and 96 hours, and 1 week. Statistical analysis with SPSS V.27 included descriptive statistics and hierarchical clustering.

Of 71 patients (62.6±15.6 years; min.12, max.84), 52 (73.2%) were women. Forty-four (61.9%) were referred due to implant dysfunction. PT were negative in 22 (31%) patients. Ten (14.1%) patients were monosensitized and 39 (54.9%) polysensitized. Clinical relevance was found in 75.5%.

Day 7 reading revealed 8 new late positive reactions to: Beryllium sulfate (Be-S), Ferric chloride (Fe-Cl), Gold sodium thiosulfate (Au-STh), Mercury (Hg), Palladium chloride (Pd-Cl), Sodium tetrachloropalladate (STCP), Tin, Titanium oxalate (Ti-Ox), Vanadium chloride (V-Cl) and oxide (V-Ox).

Most frequent positivities were Ti-Ox(n=26), Nickel (Ni)(n=23), Pd-Cl(n=21), STCP(n=21), V-Cl(n=11), V-Ox(n=8), Zinc(n=8), Rhodium chloride(n=8), Cobalt(n=5) and Au-STh(n=5). The only Ti hapten (of 5) that tested positive was Ti-Ox. Also, 2 patients with positive Ti-Ox PT had Ti-containing prosthesis and were asymptomatic, suggesting false-positives.

In cluster analysis 3 clusters stood out: patients with co-sensitization to Ni, Pd-Cl and STCP; isolated Ti-Ox sensitization; patients with other metal sensitizations. The majority of Ni-sensitized patients (82,6%) had ≥1 co-sensitization. There was no association between sensitization to Ti and to Ni. Ni (42%), Pd-Cl and STCP (38%) positivities were significantly higher in women.

Ti-Ox, Pd-Cl, and Ni were the most common sensitizers. Multiple sensitizations were more frequent in Ni-allergic patients. Women were more susceptible to Ni, Pd-Cl, and STCP sensitization. Metal sensitization was clinically relevant in 75.5% of cases. The strong association between Ni, Pd-Cl, and STCP positivity suggests cross-reactivity. No association was found between Ti sensitization and other metals, particularly Ni. The identification of two patients with Ti implants who were sensitized but asymptomatic, along with Ti-Ox being the only one of five Ti haptens to elicit reactions, highlights the need for further investigation into the rate of false positives for Ti-Ox.