Absolute Neutrophil Counts: Man Vs. Machine

Absolute Neutrophil Counts: Man vs. Machine

Problem:

Absolute Neutrophil Counts (ANC) are hallmark calculations for hematopoietic stem cell transplant (HSCT) patients as a means to accurately measure infection risk and monitor post-transplant engraftment. Historically, this calculation was done solely using data from manual differentials.  Very low white blood cell counts (WBCs) seen in this patient population make for unique challenges with accuracy due to lack of cells to count. Current advancements in accuracy and speed of laboratory instruments posed a question as to why manual differentials for ANC calculation were necessary. Other factors were the turnaround times (TAT) for manual differentials being double that of automated and significant cost difference between tests due to the labor intensity of manual testing.

Intervention:

A research study was performed using 275 specimens from ten different hematology/BMT patients over a period of two months to compare the disparity in ANC from the distinct differential types. The goal was to analyze ANC calculations to determine if data supported a change in practice to using automated differentials routinely.

Automated and manual differential results from each specimen were independently reviewed by a medical technologist and transplant nurse to verify ANC calculations from each source document.  The calculations used were: Manual ANC= [(%SEGS + % BANDS) x WBC] x 10; Automated ANC = [% NE x WBC] x 10.

Results:

Compilation of data showed the correlation factor between calculated ANCs from automated  and manual differentials to be 93% when WBC was greater than 0.7 x 10⁹/L. For lower counts the instrument accuracy in counting cells far exceeded that of the technologist as the instrument is able to detect more white cells. Standard acceptable laboratory correlation for testing with different methods is 90% or greater. Therefore, the calculated ANC results from an automated differential correspond to manual differential results proving use of automated differentials for ANCs to be warranted.

Discussion:

Study data lead to a change in practice by making CBC with automated differential the standard of practice for ANC calculation. This has significantly decreased result TAT allowing for classification of neutropenia and associated patient interventions to happen more quickly and cost effectively.