Impact of Different Pre-Dilution Methods on Routine Blood Test Results: A Study With Sysmex XN-1000

To compare three manual pre-dilution procedures with the automated undiluted mode on the Sysmex XN-1000 analyzer and to identify an optimal standard operating procedure for pre-dilution testing.

A total of 60 residual EDTA-K3 whole-blood specimens were consecutively collected between March and May 2024 and analyzed within 2 h. Each specimen was tested in the automated undiluted mode and by three manual pre-dilution procedures: direct mixing, dry-tip wiping, and wet-tip wiping. Pre-dilution was performed at 1:7 (20 μL of blood plus 120 μL of Sysmex DCL diluent) using calibrated pipettes. All procedures were performed by one trained technician. Each method was tested in triplicate, and mean values were analyzed. White blood cell count (WBC), red blood cell count (RBC), hemoglobin (HGB), platelet count (PLT), and hematocrit (HCT) were evaluated by paired t-test, Pearson correlation, Passing-Bablok regression, and bias analysis against CLIA allowable total error (TEa) criteria.

For WBC, RBC, HGB, and PLT, no significant difference was found between any pre-dilution method and the undiluted mode (all p > 0.05); for HCT, only Method 1 differed significantly (p = 0.022). Passing-Bablok regression showed that the wet-tip wiping method had the best overall agreement with the undiluted mode. TEa-based analysis showed that only Methods 2 and 3 met allowable bias limits for all five parameters.

The wet-tip wiping method showed the best overall analytical performance and may be preferred for low-volume specimens on the Sysmex XN-1000 platform.