Detection of nickel and palladium contact hypersensitivity by a flow cytometric lymphocyte proliferation test

We established a flow cytometric lymphocyte proliferation test (LPT) for the detection of nickel (Ni) and palladium (Pd) sensitization. Eighty-one consecutive patients with an indication for patch test (PT) were tested by LPT with Ni (NiSO4 ) and Pd (Na2 PdCl4 and PdCl2 ) salts. The imprecision of the LPT was low (coefficient of variation 7.2%). Using PT as a diagnostic reference, the sensitivity and specificity of LPT were 74.4% and 80% for NiSO4 , 74.4% and 78.3% for Na2 PdCl4 , and 57.2% and 85.4% for PdCl2 , respectively. For both Ni and Pd, the likelihood ratio for a positive PT markedly increased with increasing LPT value. With medical history as a reference, the sensitivity and specificity were 40.6% and 82.1% for LPT and 59.4% and 89.7% for PT, respectively. Combination of LPT and PT resulted in a higher specificity of 95%, albeit lower sensitivity of 34.4%. In conclusion, flow cytometric LPT represents a reliable and useful method for the detection of Ni and Pd sensitization. LPT values correlate with PT results and, when used in combination with PT, increase test specificity.