Correction of spurious low platelet counts by optical fluorescence platelet counting of BC-6800 hematology analyzer in EDTA-dependent pseudo thrombocytopenia patients

Abstract

Background To evaluate the dissociation effect of optical fluorescence platelet counting of BC-6800 hematology analyzer on ethylene diamine tetraacetic acid-dependent pseudo thrombocytopenia (EDTA-PTCP) samples. Methods Twenty-three finally identified EDTA-PTCP samples were recruited in this study using criteria as follow: (I) impedance platelet counts lower than 100×10 9 /L with instrument “platelet aggregation” flag; (II) existence of platelet clumps in the blood smear; (III) obviously higher platelet counts without “platelet aggregation” flag and no platelet clumps in blood smear after repeating phlebotomy using citrate anticoagulated tubes. The BC-6800 hematology analyzer and the XE-2100 hematology analyzer were used to test 23 EDTA-PTCP samples and 30 controls on both the impedance channel and the reticulocyte channel. The dissociation rate was defined as optical fluorescence platelet counts in the EDTA tubes/impedance platelet counts in citrate tubes ×100%. Results BC-6800 analyzer’s optical fluorescence platelet counts of EDTA-PTCP samples were significantly higher than impedance platelet counts (t=4.33, P=0.00) and comparable with the platelet counts of re-collected samples in tubes containing citrate anticoagulant. On BC-6800 hematology analyzer, 22 of 23 EDTA-PTCP samples showed a dissociation rate greater than 80%, and the average dissociation rate was 93%. On the XE-2100 hematology analyzer, 1 of the 17 EDTA-PTCP samples showed a dissociation rate greater than 80%, and the average dissociation rate was 56%. Conclusions Optical fluorescence platelet counting of BC-6800 Hematology Analyzer is effective for the correction of spurious low platelet counts in EDTA-PTCP patients, and its dissociation effect on EDTA-PTCP samples was independent of fluorescent dye staining.

Pseudothrombocytopenia—A Review on Causes, Occurrence and Clinical Implications

“…Indeed, PLT-F, PLT-O, and FCM displayed the highest PC, thus suggesting partial dissociation of aggregates using these techniques, as opposed to the impedance method, which was the most vulnerable to platelet clumping. This dissociation effect, independent of manufacturer's fluorescent dye staining, has been assumed in a recent Chinese study [14]. However, sample treatment with hematology or flow cytometry analyzer reagents could not be carried out in our case.…”

“…(iii) A rapid analysis of EDTA blood specimen is advocated, due to time-dependent fall in PC from 1 min after blood collection to 4 h afterwards [4,12,13]; (iv) Fluorescence platelet counting can be effective in correcting spurious low PC [14]; (v) Capillary blood is prone to platelet clumping [15], but it has been described as less rich in aggregates [16]; (vi) Alternative anticoagulants such as magnesium sulfate [5,8,17] and acid citrate dextrose (ACD) [18] are interesting tools to overcome platelets clumps. Hirudin has been studied in few reports only [8,19,20].…”

“…Depending on size, platelet clumps are then enumerated as single large platelets, or as small lymphocytes, resulting in spuriously low PC, and sometimes leading to falsely elevated leukocyte count [ 4 ]. Interestingly, the impedance histogram is a useful tool to detect PTCP, as it may display sawtooth irregularities in the curve and serrated tail, sometimes with no return to the baseline at 20 fL, along with the inability of the analyzer to determine a cut-off between platelets and red blood cell fragments or microcytic red blood cells [ 4 , 14 , 108 , 109 ].…”

“…Some parameters can positively influence platelet counting in presence of PTCP. These include the following: In vitro amikacin supplementation can prevent and dissociate platelet clumps due to EDTA, citrate [ 4 ], or heparin-PTCP [ 9 ] although controversially discussed [ 10 ]; Maintaining blood samples to 37 °C could lead to a more accurate platelet count (PC) or prevent EDTA-dependent PTCP [ 11 , 12 ]; A rapid analysis of EDTA blood specimen is advocated, due to time-dependent fall in PC from 1 min after blood collection to 4 h afterwards [ 4 , 12 , 13 ]; Fluorescence platelet counting can be effective in correcting spurious low PC [ 14 ]; Capillary blood is prone to platelet clumping [ 15 ], but it has been described as less rich in aggregates [ 16 ]; Alternative anticoagulants such as magnesium sulfate [ 5 , 8 , 17 ] and acid citrate dextrose (ACD) [ 18 ] are interesting tools to overcome platelets clumps. Hirudin has been studied in few reports only [ 8 , 19 , 20 ].…”

Pseudo-thrombocytopenia (PTCP). A challenge in the daily laboratory routine?

“…Recently, Bao et al [59] reported a new technology to measure higher platelet counts in EDTA-PTCP based on fluorescence cell analysis (SF-Cube technology), which may be suitable to solve the associated clinical problems. Platelet aggregates dissociate effectively by this technology and platelets are more correctly counted in the CDR (CBC+DIFF+RET) mode without pre-analytical management [60].…”