Aberrant lamellar body counts noted on the Beckman Coulter Unicel DxH 800

Abstract

The lamellar body count (LBC) plays a crucial role in fetal lung maturity testing. Lamellar bodies are often counted in the platelet channel of routine hematology analyzers, resulting in a rapid and inexpensive assay for fetal lung maturity. Recently, significant imprecision was noted during LBC validation on the Beckman Coulter Unicel DxH 800. The results of two Beckman Coulter Unicel DxH 800 instruments were compared to those of a Coulter LH 750 and Coulter LH 500. Three pools of amniotic fluid, commercial quality control materials, and proficiency test specimens were analyzed on all four instruments. Fifty patient specimens were also analyzed using the Coulter LH 500 and the Unicel DxH 800. The mean values and precision obtained from commercial quality control materials and proficiency test samples were comparable on all four instruments. However, many erroneously low LBC results were produced from amniotic fluid pools using both DxH 800 instruments. The erroneous values were approximately 50% lower than respective target values, occurred randomly, and affected the low, medium, and high LBC results. Inter-assay precision of the three pools ranged from 24.7 to 39.0 CV% on the DxH 800 instruments. The source of LBC errors likely involves the exclusion of smaller lamellar bodies from the counts. The DxH 800 combines new data fusion technology and mathematical algorithms to produce increased accuracy and flagging efficiency. Laboratorians should be aware that the improved specificity of the DxH 800 may preclude its use for this laboratory-developed test.