Using Smudge Cells on Routine Blood Smears to Predict Clinical Outcome in Chronic Lymphocytic Leukemia: A Universally Available Prognostic Test

Recently developed prognostic tests in early Rai and Binet stage chronic lymphocytic leukemia (CLL) require considerable technologic expertise and are not available worldwide. Smudge cells are CLL cells ruptured during smear preparation. We hypothesized that smudge cell formation is inversely correlated with expression of vimentin, a cytoskeletal protein and prognostic marker, and that the percentage of smudge cells would predict prognosis in CLL. We reviewed the blood smears of 75 patients with previously untreated early- and intermediate-stage CLL (Rai stage 0-II) who were seen at the Mayo Clinic in Rochester, Minn, between September 1989 and December 2000. A total of 200 lymphocytes and smudge cells were counted on each slide and the results expressed as a percentage of the total lymphocytes (intact and smudged). The median percentage of smudge cells was 27% (range, 4%-72%). The percentage of smudge cells inversely correlated with vimentin expression (r=-0.57; P=.007). The median percentage of smudge cells was higher in patients with the mutated immunoglobulin heavy chain gene than in those with the unmutated immunoglobulin heavy chain gene (31% vs 13%; P=.02). Patients with less than 30% smudge cells had a median time from diagnosis to initial treatment of 72.7 months, whereas the median time from diagnosis to initial treatment in patients with 30% or more smudge cells was not reached (P=.001). The percentage of smudge cells as a continuous variable correlated with overall survival (P=.04). The estimation of smudge cells on a blood smear could be a universally available prognostic test in early-stage CLL.