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.
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>
M
M
Malec
V H J
VH
van der Velden
E
E
Björklund
J M
JM
Wijkhuijs
S
S
Söderhäll
J
J
Mazur
M
M
Björkholm
A
A
Porwit-MacDonald
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