ALK rearrangement testing by fish analysis in non-small-cell lung cancer patients: Results of the first Italian external quality assurance scheme

INTRODUCTION: The Italian Association of Medical Oncology and the Italian Society of Anatomic Pathology and Diagnostic Cytopathology organized an external quality assessment (EQA) scheme for anaplastic lymphoma kinase (ALK) rearrangement by florescence in situ hybridization (FISH) analysis in non-small-cell lung cancer (NSCLC). METHODS: Sections from tissue microarrays, each including 10 NSCLC samples with known ALK status, were first validated in five referral laboratories and then provided to 37 participating centers. The laboratories were requested to perform the FISH test, using their usual protocols, and to complete the analysis within 3 weeks. By using a predefined scoring system, two points were assigned in case of correct genotype and zero points to false-negative or false-positive results. The threshold value to pass the EQA scheme was set at 18 points. Two rounds were planned. RESULTS: Thirty-four centers submitted the results within the established deadline. Several errors in the evaluation of genotype (n = 18) were reported, with both false-positive (n = 7) and false-negative (n = 11) results. Test failure occurred in seven cases. Two samples were found to be critical by two referral laboratories and seven participating centers. Twenty-six (70%) laboratories passed the first round and six the second round. Overall, 32 (86%) laboratories passed the ALK EQA scheme. CONCLUSIONS: The results of this first EQA scheme for ALK testing in NSCLC cancer patients indicate that ALK analysis is performed with adequate quality in most Italian laboratories and highlight the importance of EQA in revealing methodological problems that need to be addressed to further increase the reproducibility of molecular tests.