Peripheral blood samples are frequently screened by flow cytometry before bone marrow for suspected leukemia to facilitate treatment decisions. Criteria to establish the diagnosis of a lymphoblastic malignancy from peripheral blood are not well defined.
Retrospective comparison of paired results of peripheral blood flow cytometry and bone marrow in 383 children with ALL diagnosed consecutively at a single center from January 2007 to February 2016. Patients were aged 0-18 years and had an adequate peripheral blood sample collected up to 7 days prior to the BMA. Four-color flow cytometry was used until September 22, 2014, then a 10-color panel was established thereafter.
Of 383 patients with B or T precursor ALL and paired results, only 3 patients had discordant results. There were 2 false positives peripheral blood samples (corresponding to lymphoblastic lymphoma with BM involvement below the threshold of leukemia and ALL that initially did not meet diagnostic criteria but later progressed) and one false negative (qualitatively positive upon review). In 75% of patients (289/383) who underwent both peripheral blood flow cytometry and BMA, the diagnostic LP and first dose of IT chemo were performed during the same sedation as the BMA.
Hematopathologist experience may lead to bias.