Alicia Arenas Cortés1, Susana Olmedillas2, Juana Serrano-López1,3, Daniel Lainez-González1, Tamara Castaño1,4, Rodrigo Iñiguez5, José Luis Lopez-Lorenzo1,4, Amanda García4, Mireia Atance1,4, Rocío Nieves Salgado Sánchez1,4, Carlos Blas Lopez1,4, Mariano García Arranz2,6, Pilar Llamas Sillero1,4, Juan Manuel Alonso-Dominguez7,8. 1. Experimental Hematology, Instituto de Investigación Sanitaria Fundación Jiménez Díaz, Universidad Autónoma de Madrid, Avenida de los Reyes Católicos 2, 28040, Madrid, Spain. 2. New Therapy Group, Instituto de Investigación Sanitaria Fundación Jiménez Díaz, Universidad Autónoma de Madrid, Madrid, Spain. 3. Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain. 4. Hematology Department, Fundación Jiménez Díaz University Hospital, Madrid, Spain. 5. Hematology Department, Doce de Octubre University Hospital, Madrid, Spain. 6. Surgical Department, Medicine School, Universidad Autónoma de Madrid, Madrid, Spain. 7. Experimental Hematology, Instituto de Investigación Sanitaria Fundación Jiménez Díaz, Universidad Autónoma de Madrid, Avenida de los Reyes Católicos 2, 28040, Madrid, Spain. juan.adominguez@fjd.es. 8. Hematology Department, Fundación Jiménez Díaz University Hospital, Madrid, Spain. juan.adominguez@fjd.es.
Abstract
BACKGROUND: BCR-ABL1/ABL1 p210 measurement by quantitative polymerase chain reaction (qPCR) is used worldwide to monitor the molecular response in chronic myeloid leukemia (CML) patients. Droplet digital polymerase chain reaction (ddPCR) seems to show a greater sensitivity than qPCR, probably due to the high number of replicates analyzed in ddPCR for the comparison. Additionally, in a recently published comparison, ddPCR measurements were not adequately transformed into International Scale (IS). METHOD: We have analyzed 50 CML patients and ten non-CML donors in parallel by qPCR and ddPCR. To the best of our knowledge, this is the first study comparing both techniques under similar conditions, with BCR-ABL1/ABL1 measurements performed via both techniques transformed into IS. RESULTS: Qualitative and quantitative comparisons showed excellent results. The qualitative correlation showed a Kappa index of 0.94 (95% confidence interval [CI] 0.90-0.98) (P < 0.001). In the quantitative comparison, the absolute intra-class correlation coefficient was 0.868 (95% CI 0.734-0.937; P < 0.001), and Lin's concordance correlation coefficient was 0.863. The Passing-Bablock test indicated a slight proportional difference between qPCR and ddPCR. A quantitative and qualitative subanalysis including 40 patients with a molecular response of 3.0 or deeper showed similar results in every test. In addition, the proportional difference in the Passing-Bablock test disappeared. There were no differences in the sensitivity for BCR-ABL1 detection between qPCR and ddPCR (McNemar test, P = 0.5). CONCLUSIONS: In conclusion, our results show very good quantitative and qualitative correlations between BCR-ABL1/ABL1 p210 results obtained by qPCR and by ddPCR and confirm previous scarce data regarding the lack of an increase in sensitivity of ddPCR over qPCR in this setting.
BACKGROUND:BCR-ABL1/ABL1 p210 measurement by quantitative polymerase chain reaction (qPCR) is used worldwide to monitor the molecular response in chronic myeloid leukemia (CML) patients. Droplet digital polymerase chain reaction (ddPCR) seems to show a greater sensitivity than qPCR, probably due to the high number of replicates analyzed in ddPCR for the comparison. Additionally, in a recently published comparison, ddPCR measurements were not adequately transformed into International Scale (IS). METHOD: We have analyzed 50 CMLpatients and ten non-CML donors in parallel by qPCR and ddPCR. To the best of our knowledge, this is the first study comparing both techniques under similar conditions, with BCR-ABL1/ABL1 measurements performed via both techniques transformed into IS. RESULTS: Qualitative and quantitative comparisons showed excellent results. The qualitative correlation showed a Kappa index of 0.94 (95% confidence interval [CI] 0.90-0.98) (P < 0.001). In the quantitative comparison, the absolute intra-class correlation coefficient was 0.868 (95% CI 0.734-0.937; P < 0.001), and Lin's concordance correlation coefficient was 0.863. The Passing-Bablock test indicated a slight proportional difference between qPCR and ddPCR. A quantitative and qualitative subanalysis including 40 patients with a molecular response of 3.0 or deeper showed similar results in every test. In addition, the proportional difference in the Passing-Bablock test disappeared. There were no differences in the sensitivity for BCR-ABL1 detection between qPCR and ddPCR (McNemar test, P = 0.5). CONCLUSIONS: In conclusion, our results show very good quantitative and qualitative correlations between BCR-ABL1/ABL1 p210 results obtained by qPCR and by ddPCR and confirm previous scarce data regarding the lack of an increase in sensitivity of ddPCR over qPCR in this setting.