and RDW values are comparable by both methods with a slightly lower MCV noted by the manual method. PLT For this study, a FCM reference procedure was used to accurately validate PLT counts from the newly developed DxH 800 analyzer. Samples analyzed by FCM were in the PLT range of 1 to 1297 · 109/l (n = 256). The DxH 800 showed a strong correlation with both the LH 780 and the FCM (r2 = 0.996 and r2 = 0.985, respectively). The DxH 800 gave accurate results when compared to both the LH 780 and the FCM (P = 0.804, ANOVA) with a small, statistically insigniﬁcant negative bias (Table 2). The accuracy improved when samples that were ﬂagged for review were excluded. A subset of all the samples (n = 57) contained megathrombocytes, a cellular characteristic that potentially could inﬂuence the PLT count. The DxH 800 showed strong correlation with both reference data sets again (LH 780 and FCM, Figure 2b) with r2 values of 0.996 and 0.974, respectively. A second sub- Figure 2. Platelet (PLT) enumera- tion. (a) PLT counts for all sam- ples collected (n = 257) on the DxH 800 and LH 780 vs. ﬂow cytometry (FCM). r2 Values for DxH 800 vs. LH 780 and DxH 800 vs. FCM were 0.996 and 0.985, respectively. (b) PLT counts in the presence of mega- thrombocytes (manually con- ﬁrmed) on DxH 800 and LH 780 compared to the reference FCM. r2 Values for DxH 800 vs. LH 780 and DxH 800 vs. FCM were 0.996 and 0.974, respectively. (c) PLT counts in the presence of microcytosis (manually con- ﬁrmed) on the DxH 800 vs. LH 780 compared to the reference FCM. r2 Values for DxH 800 vs. LH 780 and DxH 800 vs. FCM were 0.998 and 0.966, respec- tively. (a) (c) 2010 Blackwell Publishing Ltd, Int. Jnl. Lab. Hem. 2011, 33, 45–56 B. D. HEDLEY ET AL. DXH 800 PERFORMANCE EVALUATION 51 set of samples containing microcytic or fragmented RBCs (n = 28) were evaluated and again the DxH 800 analyzer demonstrated good correlation with the LH 780 and FCM data (Figure 2c) with r2 values of 0.998 and 0.966, respectively. Both of these PLT subsets showed no signiﬁcant difference between groups (ANO- VA, P = 0.514 and P = 0.903, respectively). PLT accu- racy data at <50, <20, <10 · 109/l PLTs are shown in Table 4 show an impressive performance, particularly in the lower ranges. Of particular note, those samples Table 4. Platelet (PLT) sensitivity and speciﬁcity values for the DxH 800 vs. ﬂow cytometry PLT count (·109/l) Sensitivity TP/(TP + FN) Speciﬁcity TN/(TN + FP) <10 <20 <50 92.3% 83.3% 96.6% 100% 97.6% 95.1% False negative 1/13* 5/30† 2/58‡ *This single value has a value of 10.3. †All samples were ﬂagged for review by the DxH 800. ‡These two samples only showed a small difference in PLT count. (b)