Multicenter evaluation of the analytical and clinical performance of the Elecsys® S100 immunoassay in patients with malignant melanoma

The aim of this multicenter study was to evaluate the technical and clinical performance of the Elecsys® S100 electrochemiluminescence immunoassay and to assess its utility as a tumor marker in patients with malignant melanoma. Imprecision studies yielded within-run coefficients of variation (CVs) of 0.7-2.0% and between-day CVs of 1.0-6.4%. Serum samples that were distributed to 11 participating laboratories for a comparability analysis resulted in excellent recoveries of 93-105% related to the median for all laboratories. The functional sensitivity of the assay was determined to be below 0.02 μg/L. The lot-to-lot reproducibility of Elecsys® S100 was tested by analyzing 110 sera with three different reagent lots on an E2010 analyzer. This lot-to-lot comparison showed excellent correlation, with a coefficient of 0.99. A 95th percentile cut-off value of 0.10 μg/L was calculated from values measured in 206 healthy individuals. Using this cut-off value, sensitivity of 41% was found, with positive and negative predictive values of 0.50 and 0.91, respectively. Method comparison with the Sangtec® 100 luminescence immunoassay, run on two different analyzers, showed correlation with coefficients ranging from 0.76 to 0.95. A comparison of S100 values obtained with both tests showed identical patterns in 68 serial samples from 15 patients with malignant melanoma during follow-up. These findings indicate that serial measurements with the Elecsys® S100 assay are useful for the follow-up and monitoring of therapy in patients with malignant melanoma.