Neutropenia: the accuracy and precision of the neutrophil count in leukopenic patients

Is a 500-Cell Count Necessary for Bone Marrow Differentials?: A Proposed Analytical Method for Validating a Lower Cutoff

OBJECTIVES

By convention, 500 cells are counted for bone marrow aspirate differentials. Evidence supporting such a cutoff is lacking. We hypothesized that 300-cell counts could be sufficient.

METHODS

Cell count results from 165 cases, for which values were recorded at 300 and 500 cells, were analyzed. We tested for statistical differences and changes in diagnostic classification between the two cutoffs.

RESULTS

Three hundred cell counts did not produce diagnostically different results, particularly for myeloblasts and plasma cells, where cell percentages are critical for disease classification. Method comparison analysis did not reach statistical significance for any cell type when comparing the two methods. Bias plots showed narrow, even spread about the mean bias. Contingency table analysis yielded no significant diagnostic discrepancies.

CONCLUSIONS

Performing differential counts on 300 cells would produce clinically and statistically similar results to 500 cells. Reducing the cell number counted has potential cost/labor reductions without affecting quality of care.

Absolute neutrophil counts from automated hematology instruments are accurate and precise even at very low levels

Using 106 samples from patients with an absolute neutrophil count (ANC) less than 2.0 × 10(9)/L, two 5-part differential hematology instruments (Sysmex XE-2100, Sysmex, Kobe, Japan, and Advia 2120i, Siemens Healthcare Diagnostics, Deerfield, IL), two 3-part differential hematology instruments (Sysmex K4500, Sysmex, and Advia 60, Siemens Healthcare Diagnostics), and an automated system for examination of microscopic slides (CellaVision DM96, CellaVision, Lund, Sweden) were compared with a flow cytometric (FCM) neutrophil count using monoclonal antibodies for cell classification. The precision and accuracy of the 5-part differential instrument ANC was very good at more than 0.1 × 10(9)/L, although a small systematic difference (10.3%) was found between the 2 instruments. The ANC of the 3-part differential instruments was less reliable, but the WBC count correlated very well with the WBC count from the 5-part differential instruments. Also, the neutrophil count from the CellaVision DM96 compared very well with FCM. When used in the correct laboratory setting, all of the evaluated instruments provide ANCs and WBCs with adequate accuracy and precision.