Table 5. Nucleated red blood cell false positive and false negative rates, sensitivity, speciﬁcity, and biases on the LH 780 and DxH 800 FP rate FN rate Sensitivity Speciﬁcity Bias LH 780 3% 10% 56% 96% )0.29 DxH 800 0% 6% 73% 100% )0.60 NRBC parameter ﬂagged for review was reduced from 24% on the LH 780 to 14% on the DxH 800. Increased sensitivity and speciﬁcity, much improved correlation in particular in the range of 2–10 NRBCs (DxH 800 vs. FCM, r2 = 0.806 from LH 780 vs. FCM, r2 = 0.444), and decreased false negative/positive rate indicate that the DxH 800 is signiﬁcantly better at detecting and enumerating NRBCs. D I S C U S S I O N The CBC performed by current laboratory instruments is fast, reliable, and accurate on hematologically nor- mal samples (Aulesa et al., 2003; Bourner, Dhaliwal & Sumner, 2005). When all parameters are within nor- mal ranges, the enumeration of cellular elements including a ﬁve-part differential are available for reporting in under a minute from presentation of the sample to the instrument. This process slows down considerably when the indices enumerated stray from normal values or there are abnormalities within the sample that cause ﬂagging or interference, necessitat- ing veriﬁcation of the results prior to reporting. Cellu- lar interference may inﬂuence the WBC count, giant or clumped PLTs may inﬂuence PLT enumeration leading to inaccurate clinical decision making, and the accurate detection and enumeration of NRBCs may indicate the presence of hematological or nonhemato- logical disease (Schwartz & Stansbury, 1954; Harrison et al., 2005; Segal et al., 2005; Bodey, 2009). Samples were accrued for determining the accuracy of the new DxH 800 in the ranges of 0.1 to 190.4 · 109/l for WBC, 1 to 1297 · 109/l for PLTs, and 0–61 NRBCs/100 WBCs. All samples were exam- ined to conﬁrm the accuracy and precision of the new DxH 800 analyzer compared to the predicate analyzer, LH 780, and Flow Cytometer Methods (FCMs) for 2010 Blackwell Publishing Ltd, Int. Jnl. Lab. Hem. 2011, 33, 45–56 B. D. HEDLEY ET AL. DXH 800 PERFORMANCE EVALUATION 53 total WBC, PLT and NRBC counts. WBC differentials were not compared in this study but may be the objective of future studies. The DxH 800 provides extremely precise and accurate PLT and WBC counts over an impressive reporting range considering that the samples were preselected based on abnormal hematological parameters. The DxH 800 also performs appropriate and accurate correction of red cell param- eters in the presence of extreme leukocytosis ( 140 · 109/l). WBC and PLT enumeration in the presence of interference results in a lower review rate and faster turn around times with the DxH 800, when compared to the LH 780. When compared to FCM, the DxH 800 shows no bias in WBC count and PLTs in the lower range; however, with higher PLT and NRBC counts, the DxH 800 shows a slight negative bias. The negative bias with high PLT values (which is not seen at PLT values <50 · 109/l) may be attributed to the FCM reference. This reference method was originally developed for low PLTs numbers (<50 · 109/l) and although a correction for higher PLT numbers (>500 · 109/l) was used the FCM tends to overestimate the PLT value. This could account for the discordance seen in the clinically insigniﬁcant higher range between the DxH 800 and the FCM. The DxH 800 cellular analysis system combines mechanical and technological improvements over pre- vious analyzers resulting in 10 times more data col- lected per sample and translating into improved accuracy and precision. The demand for accurate and precise automated enumeration of WBC counts is dri- ven by the demand placed on hematology laboratories for rapid turnaround times on samples with abnormal features. For WBC enumeration the most common features for interference that generate ‘ﬂags’ are NRBCs, megathrombocytes, PLT clumping, and WBC counts in the lower range of linearity. Patients receiv- ing active chemotherapy as cancer treatment require rapid and accurate results to allow for decisions on continuing treatment or to offer salvage therapy (Nav- arro et al., 1998; Springer, von Ruecker & Dickerhoff, 1998; Sagmeister, Oec & Gmur, 1999; Cosler et al., 2005; Nevo et al., 2007; Oka et al., 2007; Slichter, 2007; Dranitsaris et al., 2008; Bodey, 2009). Our laboratory evaluated the new DxH 800 and found that this new cellular analysis system is capable of providing accurate WBC counts in the presence of interfering particles and in the extreme low range