In vitro testing for cobalt sensitivity: an aid to diagnosis.

Peripheral blood lymphocytes from 45 patients with a positive patch test to cobalt chloride (CoCl2) and 37 controls were stimulated with various concentrations of CoCl2 and/or cobalt sulphate (CoSO4) or cobalt nitrate (Co(NO3)2) or cobalt acetate [CH3COO)2Co) for various days in culture. Lymphocytes from 35 of these patients showed a significantly greater response than that of the controls. The response occurred in the T enriched population and was monocyte dependent. The strength of the in vivo serial dilution test results did not correlate well with the height of in vitro responses. Lymphocytes from 3 nickel and/or chromium sensitive patients failed to respond to stimulation with cobalt compounds thus confirming the specificity of the reaction. The DNA synthesis test seems to be a reliable in vitro method to aid in the diagnosis of cobalt sensitivity.