Interlaboratory Evaluation of a New Reverse Transcriptase Polymerase Chain Reaction–Based Enzyme-Linked Immunosorbent Assay for the Detection of Circulating Melanoma Cells: A Multicenter Study of the Dermatologic Cooperative Oncology Group

PURPOSE: Reverse transcription-polymerase chain reaction (RT-PCR)–based detection of tyrosinase mRNA is the most frequently used laboratory method for the detection of circulating tumor cells in melanoma patients. However, previously published results showed considerable variability in the PCR positivity rates. MATERIALS AND METHODS: We designed a collaborative study to assess the sensitivity, specificity, and clinical relevance of a new standardized RT-PCR–based enzyme-linked immunosorbent assay (ELISA) for the detection of circulating melanoma cells. Blood samples of healthy donors mixed with cells of a melanoma cell line were prepared in a blinded fashion, and aliquots were sent to seven participating laboratories experienced in RT-PCR. RESULTS: The results demonstrate a high sensitivity (1 melanoma cell/mL blood) and specificity (no false-negatives and 7.4% [2 of 28] false-positives) of the assay and a satisfactory rate of interlaboratory reproducibility. The analysis of aliquots of blinded samples de...