In this investigation the notion 'sensitivity' of the test method also used by the Nickel Test Sensitive is defined as follows: Sensitivity = is defined as the number of true positive test results divided by (the number of true positive + the number of false negative test results). True positive reactions were defined as 'positive DMG-test reactions that were confirmed by a nickel release above 0.5 μg nickel . cm-2 . week-1'. False negative test results were defined as 'negative DMG-test reactions but where nickel release was above 0.5 μg nickel . cm -2 . week-1'. Thus, the true prevalence of materials that release too much nickel will be underestimated if one only relies on positive DMG test results.