Analysis of minimal residual disease in childhood acute lymphoblastic leukemia: comparison between RQ-PCR analysis of Ig/TcR gene rearrangements and multicolor flow cytometric immunophenotyping.
Detection of minimal residual disease (MRD) in follow-up samples from patients with ALL is essential for evaluation of treatment response. We applied multicolor flow cytometry and real-time quantitative PCR (RQ-PCR) to compare MRD results in 71 follow-up samples from 22 children treated for ALL. When results obtained by flow cytometry and RQ-PCR were grouped into positive-negative categories, a significant level of agreement was found in 72% of samples (P<0.001). However, if a cutoff level of 0.01% was applied, the concordance was 89%. MRD could be quantified in 19 samples by both methods, showing a strong correlation (P<0.01). Nevertheless, MRD levels differed more than five-fold between both methods in 4/19 samples. In 20 (28%) samples, the two techniques showed discordant results. Most discordant results (17/20) were due to the limited sensitivity of flow cytometry analysis within the range 0.01-0.001%; remaining discordant results were due to the instable or subclonal IG/TCR gene rearrangements or a limited quantitative range of the applied RQ-PCR targets. Although concordant results could be obtained by flow cytometry and RQ-PCR analysis, MRD levels may differ. Therefore, MRD data obtained by these two techniques are not yet easily exchangeable.
Malec
M
M
Department of Pathology, Astrid Lindgren Child Hospital, Karolinska Institutet at Karolinska University Hospital, Stockholm, Sweden. maria.malec-zacharski@cmm.ki.se <maria.malec-zacharski@cmm.ki.se>
van der Velden
V H J
VH
Björklund
E
E
Wijkhuijs
J M
JM
Söderhäll
S
S
Mazur
J
J
Björkholm
M
M
Porwit-MacDonald
A
A
D000293:Adolescent; D001853:Bone Marrow / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D005260:Female; D005434:Flow Cytometry; D015329:Gene Rearrangement, T-Lymphocyte; D005803:Genes, Immunoglobulin; D019672:Genes, T-Cell Receptor; D006801:Humans; D016130:Immunophenotyping; D007223:Infant; D008297:Male; D018365:Neoplasm, Residual / Q000175:diagnosis / Q000235:genetics*; D016133:Polymerase Chain Reaction; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000175:diagnosis / Q000235:genetics; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000175:diagnosis / Q000235:genetics