THE USE OF IGH FINGERPRINTING AND ASO-DEPENDENT - PCR FOR THE INVESTIGATION OF RESIDUAL DISEASE (MRD) IN ALL

In acute lymphoblastic leukaemia (ALL), investigation of minimal resid ual disease by conventional morphology and immunology fails to detect levels of residual disease of <1 leukaemic in 10-100 normal cells. The use of polymerase chain reaction (PCR) to exploit the diversity of th e complementarity determining region (CDR) and immunoglobulin variable heavy chain (VH) family specific usage has greatly improved the sensi tivity up to one leukaemic cell in 10(5)-10(6) normal bone marrow cell s, Here we report on a prospective study of 14 patients with ALL of B- cell lineage by using a combined PCR approach which estimates levels o f disease between 1:10(3) and 1:10(5). The sequential use of allele-sp ecific oligoprimer (ASO) independent tests (using framework 1, FR1 and 3, FR3 primers with a JH consensus primer, sensivity up to 1:5 x 10(3 )) and ASO-dependent PCR (sensitivity up to 1:10(5)) assays were appli ed to 64 bone marrow (BM) follow-up samples in a sequential array of t ests. Results presented in this study indicate high concordance of MRD among different tests for samples with level of residual disease >1:5 x 10(3). Consequently, samples positive by the FR1 and I:R3 fingerpri nting tests were confirmed by the more sensitiive ASC)-dependent tests , as expected, However, the ASO-dependent assays revealed levels of di sease undetected by the FR1 and FR3 test. Although a higher level of s ensitivity is provided by the ASO-dependent tests, the FR1 and FR3 fin gerprinting tests allow MRD investigation in patients with oligoclonal B cell proliferations, CDR3 region of size <15 bp or with ASO primers unsuitable for PCR investigation on technical grounds (i.e. backgroun d signal). If a sequential order of investigation from less (e.g. FR1 anti FR 3 fingerprinting to more sensitive tests (ASO-dependent) is ap plied, an indirect estimate of MRD is obtained for patients with level of disease <1:10(3).