Platinum concentrations in sera of catalyst production workers are not predictive of platinum salt allergy

Platinum (Pt) salts are potent occupational allergens in precious metal refineries and catalyst productions. The threshold limit value of 2000 ng soluble Pt/m3 enforced in many countries has been questioned because there is still a high incidence of Pt salt allergy. The objective of the present case series is to define the predictive value of biological monitoring by relating Pt in the serum of catalyst production workers and control subjects to sensitization to Pt salts as assessed by skin prick testing. A total of 38 Pt measurements were taken from sera of six workers investigated several times during a 5-year cohort study. Three subjects showed a conversion of skin prick test (SPT) with Pt salts from negative to positive during the cohort study (all considered highly exposed to Pt), and three did not show SPT conversion. Previous therapy with Pt-containing anti-cancer drugs and metallic dental alloys were considered as confounders. Only one of the three workers sensitized to Pt salt had clearly elevated serum Pt concentrations, but this elevation was not observed in each examination. Elevated Pt concentrations were also found in two subjects with low or no exposure to Pt. Both had metallic dental alloys. One control subject without metallic dental alloys showed low Pt concentrations in the serum in four examinations, but a single unexplained high concentration in his initial examination. In this small case series, serum Pt concentrations were neither sensitive nor specific for the prediction of Pt salt sensitization. Low specificity may be explained by Pt-containing metallic dental alloys, but additional unknown confounders may be of importance.