Feasibility of Counting Smudge Cells as Lymphocytes in Differential Leukocyte Counts Performed on Blood Smears of Patients With Established or Suspected Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma.

BACKGROUND

Lymphocytosis and smudge cells are commonly observed on the blood smears of patients with an established or suspected diagnosis of chronic lymphocytic leukemia/small lymphocytic lymphoma. Excluding smudge cells from the manual differential count (MDIFF), a common laboratory practice, yields unreliable results and consequently necessitates performing the MDIFF testing on an albuminized blood smear.

OBJECTIVE

To assess the reliability of counting smudge cells as lymphocytes in the MDIFFs on nonalbuminized smears and automated differentials (ADIFFs) as a substitute for MDIFFs.

METHODS

We compared corresponding results of MDIFFs on nonalbuminized smears vs MDIFFs on albuminized smears (group A, n  = 82), ADIFFs vs MDIFFs on nonalbuminized smears (group B, n  = 68), and ADIFF vs MDIFFs on albuminized smears (group C, n  = 50). Smudge cells on the nonalbuminized smears were counted as lymphocytes. We focused on 2 white blood cell types: neutrophils and lymphocytes.

RESULTS

Respective means for % lymphocytes and % neutrophils were 83.2 vs 83.2 and 14.0 vs 13.6 for Group A, 75.0 vs 77.0 and 20.2 vs 19.8 for Group B, and 76.1 vs 79.3 and 18.7 vs 17.4 for Group C. Respective correlation coefficients for % lymphocytes and % neutrophils were 0.92 and 0.94 for group A, 0.94 and 0.97 for group B, and 0.88 and 0.92 for group C.

CONCLUSION

Counting smudge cells as lymphocytes on nonalbuminized blood smears yielded reliable MDIFF results. Reportable ADIFF results were generated by the analyzer on 73% of the specimens, of which 93% were reliable.