Variability in absolute lymphocyte counts obtained by automated cell counters

Area of Science:

• Hematology
• Clinical Laboratory Science
• Immunology

Background:

• Increasing interest in absolute lymphocyte counts, particularly for monitoring human immunodeficiency virus (HIV) patients.
• Absolute lymphocyte counts are crucial for determining lymphocyte subset values, such as absolute CD4+ counts.
• Current methods combine routine hematology results with flow cytometry data.

Purpose of the Study:

• To investigate the analytic variability in absolute lymphocyte count determination.
• To compare the variability of absolute lymphocyte counts with that of total white blood cell (WBC) counts.
• To assess the impact of different automated methods on lymphocyte count accuracy.

Main Methods:

• Comparison of four automated cell counters (Technicon H*1, TOA NE8000, Coulter STKS, Abbott CD3000) against each other and manual eye counts.
• Analysis of 524 patient specimens.
• Evaluation of analytic variability for absolute lymphocyte counts and total WBC counts.

Main Results:

• Analytic variability for absolute lymphocyte counts was 12.4%, significantly higher than the 4.9% for total WBC counts.
• Method variability was the primary driver of analytic variability in absolute lymphocyte counts.
• Variability in absolute lymphocyte counts exceeded that typically seen in interlaboratory trials for relative CD4 counts.

Conclusions:

• Significant analytic variability exists in automated absolute lymphocyte count methods.
• Method-specific biases in cell classification algorithms limit calibration effectiveness.
• Expressing flow cytometry results as fractions of leukocytes and total lymphocytes, with subsequent WBC count determination, may yield more precise absolute values.