Peripheral Blood Lymphocyte Typing as a Useful Tool to Objectify the Oral Mucosa Patch Test in the Diagnosis of Allergic Contact Mucositis to Nickel Marco Di Tola & Rachele Amodeo & Mariacatia Marino & Fabio Tabacco & Rossella Casale & Maurizio Bove & Alfredo Rossi & Patrizia Cardelli & Antonio Picarelli Received: 21 March 2014 /Accepted: 17 April 2014 # Springer Science+Business Media New York 2014 Abstract Nickel (Ni) exposure through the intestinal mucosa may cause a hypersensitivity reaction recently defined as allergic contact mucositis (ACM). This condition is identifi- able by the oral mucosa patch test (omPT), a qualitative and subjective examination that requires clinical expertise. Our aim was to evaluate if a peripheral blood lymphocyte typing performed before and after the omPT for Ni may be able to objectify this examination for diagnostic purposes. Thirty patients with symptoms referable to the ingestion of Ni-rich foods were subjected to omPT for Ni. Before and after the omPT, each patient underwent blood sampling for the typing of total lymphocytes and their subsets (T, T helper or Th, T cytotoxic or Tc, B, natural killer or NK). Statistical analysis was performed by Student t test and receiver operating char- acteristic (ROC) curve analysis. According to the omPT out- comes, 18 patients were defined as Ni-sensitive and the re- maining 12 as controls. In Ni-sensitive patients, the number of total, T, Th, Tc, and B lymphocytes/μL whole blood increased after the omPT (p <0.0001 for the first three, p =0.0004 and p =0.0001 for the last two lymphocyte types). No omPT- dependent lymphocyte increase was observed in controls. The post/pre omPT cell ratio, especially if calculated for Th lymphocytes, appears to be an effective index for diagnostic purposes (sensitivity=100 %, specificity=83.3 %, Youden index=0.833, area under curve (AUC)=0.926, p <0.0001). In conclusion, the peripheral blood lymphocyte typing with calculation of post/pre omPT cell ratio has the potential to support the omPT in diagnosing ACM, with the advantage of providing quantitative and objective data. Keywords Allergic contact mucositis . Nickel . Oral mucosa patch test . Peripheral blood lymphocyte typing . Post/pre omPT cell ratio Introduction Nickel (Ni) is a transition metal widespread in the environ- ment, foods, drugs, chemicals, and metallic utensils [1]. In 2008, the American Contact Dermatitis Society has defined this ubiquitous element as the Contact Allergen of the Year [2]. The prevalence of Ni allergy is indeed growing in many countries and represents a major health and socioeconomic issue. Researches published over the last 40 years from North America to Western Europe highlight a median prevalence of 8.6 %, with values higher among women than men (17.1 vs. 3 %) [3–5]. The skin contact with Ni may cause an allergic contact dermatitis (ACD), for which the epicutaneous patch test (ePT) is considered the gold standard for its diagnosis [6]. Similarly, the ingestion of Ni-rich foods can result in a systemic hyper- sensitivity with dermatologic manifestations or symptoms such as diarrhea, headache, and general discomfort [5, 7, 8]. The allergic contact mucositis (ACM) has been recently de- scribed as a systemic Ni hypersensitivity identifiable by the oral mucosa patch test (omPT) [9]. However, both ePT and M. Di Tola (*) : M. Marino : R. Casale : A. Picarelli Department of Internal Medicine and Medical Specialties, Sapienza University-Polyclinic Umberto I, Viale del Policlinico 155, 00161 Rome, Italy e-mail: marco.ditola@uniroma1.it R. Amodeo : F. Tabacco : P. Cardelli UOC Laboratory Diagnostics, S. Andrea Hospital, Rome, Italy M. Bove : P. Cardelli Department of Clinical and Molecular Medicine, Sapienza University, Rome, Italy A. Rossi Department of Dermatology and Plastic Surgery, Sapienza University, Rome, Italy Biol Trace Elem Res DOI 10.1007/s12011-014-9991-x